diff mbox

[RFC] pci: ACS quirk for AMD southbridge

Message ID 20120712050653.20439.11009.stgit@bling.home (mailing list archive)
State New, archived
Headers show

Commit Message

Alex Williamson July 12, 2012, 5:18 a.m. UTC 
We've confirmed that peer-to-peer between these devices is
not possible.  We can therefore claim that they support a
subset of ACS.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: Joerg Roedel <Joerg.Roedel@amd.com>
---

Two things about this patch make me a little nervous.  The
first is that I'd really like to have a pci_is_pcie() test
in pci_mf_no_p2p_acs_enabled(), but these devices don't
have a PCIe capability.  That means that if there was a
topology where these devices sit on a legacy PCI bus,
we incorrectly return that we're ACS safe here.  That leads
to my second problem, pciids seems to suggest that some of
these functions have been around for a while.  Is it just
this package that's peer-to-peer safe, or is it safe to
assume that any previous assembly of these functions is
also p2p safe.  Maybe we need to factor in device revs if
that uniquely identifies this package?

Looks like another useful device to potentially quirk
would be:

00:15.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 0)
00:15.1 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 1)
00:15.2 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 2)
00:15.3 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 3)

00:15.0 0604: 1002:43a0
00:15.1 0604: 1002:43a1
00:15.2 0604: 1002:43a2
00:15.3 0604: 1002:43a3

 drivers/pci/quirks.c |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)


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Comments

Andreas Hartmann July 12, 2012, 4:29 p.m. UTC | #1 
Hello Alex,

I tested the patch below against linux 3.4.4 and with this
PCI WLAN-device:

06:07.0 Network controller: Ralink corp. RT2800 802.11n PCI
06:07.0 0280: 1814:0601

The device resides behind a PCI to PCI bridge:

00:14.4 PCI bridge: Advanced Micro Devices [AMD] nee ATI SBx00 PCI to PCI Bridge (rev 40) (prog-if 01 [Subtractive decode])
00:14.4 0604: 1002:4384 (rev 40) (prog-if 01 [Subtractive decode])

The device works fine in kvm / 64bit. Surprisingly, it isn't necessary
at all to put the PCI to PCI bridge to the VM. It's enough to put the
WLAN-device to the VM and bind it to vfio-pci. That's all. The bridge
isn't bound to vfio-pci (it's bound to nothing).

I stripped off linux-pci because I'm no member of this list.


Thanks.
kind regards,
Andreas


Alex Williamson wrote:
> We've confirmed that peer-to-peer between these devices is
> not possible.  We can therefore claim that they support a
> subset of ACS.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: Andreas Hartmann <andihartmann@01019freenet.de>
> Cc: Joerg Roedel <Joerg.Roedel@amd.com>
> ---
> 
> Two things about this patch make me a little nervous.  The
> first is that I'd really like to have a pci_is_pcie() test
> in pci_mf_no_p2p_acs_enabled(), but these devices don't
> have a PCIe capability.  That means that if there was a
> topology where these devices sit on a legacy PCI bus,
> we incorrectly return that we're ACS safe here.  That leads
> to my second problem, pciids seems to suggest that some of
> these functions have been around for a while.  Is it just
> this package that's peer-to-peer safe, or is it safe to
> assume that any previous assembly of these functions is
> also p2p safe.  Maybe we need to factor in device revs if
> that uniquely identifies this package?
> 
> Looks like another useful device to potentially quirk
> would be:
> 
> 00:15.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 0)
> 00:15.1 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 1)
> 00:15.2 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 2)
> 00:15.3 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 3)
> 
> 00:15.0 0604: 1002:43a0
> 00:15.1 0604: 1002:43a1
> 00:15.2 0604: 1002:43a2
> 00:15.3 0604: 1002:43a3
> 
>  drivers/pci/quirks.c |   29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 4ebc865..2c84961 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3271,11 +3271,40 @@ struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
>  	return pci_dev_get(dev);
>  }
>  
> +/*
> + * Multifunction devices that do not support peer-to-peer between
> + * functions can claim to support a subset of ACS.  Such devices
> + * effectively enable request redirect (RR) and completion redirect (CR)
> + * since all transactions are redirected to the upstream root complex.
> + */
> +static int pci_mf_no_p2p_acs_enabled(struct pci_dev *dev, u16 acs_flags)
> +{
> +	if (!dev->multifunction)
> +		return -ENODEV;
> +
> +	/* Filter out flags not applicable to multifunction */
> +	acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
> +
> +	return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
> +}
> +
>  static const struct pci_dev_acs_enabled {
>  	u16 vendor;
>  	u16 device;
>  	int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
>  } pci_dev_acs_enabled[] = {
> +	/*
> +	 * AMD/ATI multifunction southbridge devices.  AMD has confirmed
> +	 * that peer-to-peer between these devices is not possible, so
> +	 * they do support a subset of ACS even though the capability is
> +	 * not exposed in config space.
> +	 */
> +	{ PCI_VENDOR_ID_ATI, 0x4385, pci_mf_no_p2p_acs_enabled },
> +	{ PCI_VENDOR_ID_ATI, 0x439c, pci_mf_no_p2p_acs_enabled },
> +	{ PCI_VENDOR_ID_ATI, 0x4383, pci_mf_no_p2p_acs_enabled },
> +	{ PCI_VENDOR_ID_ATI, 0x439d, pci_mf_no_p2p_acs_enabled },
> +	{ PCI_VENDOR_ID_ATI, 0x4384, pci_mf_no_p2p_acs_enabled },
> +	{ PCI_VENDOR_ID_ATI, 0x4399, pci_mf_no_p2p_acs_enabled },
>  	{ 0 }
>  };
>  
> 
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Bjorn Helgaas June 26, 2013, 4:15 a.m. UTC | #2 
On Wed, Jul 11, 2012 at 11:18 PM, Alex Williamson
<alex.williamson@redhat.com> wrote:
> We've confirmed that peer-to-peer between these devices is
> not possible.  We can therefore claim that they support a
> subset of ACS.
>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Cc: Joerg Roedel <Joerg.Roedel@amd.com>
> ---
>
> Two things about this patch make me a little nervous.  The
> first is that I'd really like to have a pci_is_pcie() test
> in pci_mf_no_p2p_acs_enabled(), but these devices don't
> have a PCIe capability.  That means that if there was a
> topology where these devices sit on a legacy PCI bus,
> we incorrectly return that we're ACS safe here.  That leads
> to my second problem, pciids seems to suggest that some of
> these functions have been around for a while.  Is it just
> this package that's peer-to-peer safe, or is it safe to
> assume that any previous assembly of these functions is
> also p2p safe.  Maybe we need to factor in device revs if
> that uniquely identifies this package?
>
> Looks like another useful device to potentially quirk
> would be:
>
> 00:15.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 0)
> 00:15.1 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 1)
> 00:15.2 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 2)
> 00:15.3 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 3)
>
> 00:15.0 0604: 1002:43a0
> 00:15.1 0604: 1002:43a1
> 00:15.2 0604: 1002:43a2
> 00:15.3 0604: 1002:43a3
>
>  drivers/pci/quirks.c |   29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 4ebc865..2c84961 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3271,11 +3271,40 @@ struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
>         return pci_dev_get(dev);
>  }
>
> +/*
> + * Multifunction devices that do not support peer-to-peer between
> + * functions can claim to support a subset of ACS.  Such devices
> + * effectively enable request redirect (RR) and completion redirect (CR)
> + * since all transactions are redirected to the upstream root complex.
> + */
> +static int pci_mf_no_p2p_acs_enabled(struct pci_dev *dev, u16 acs_flags)
> +{
> +       if (!dev->multifunction)
> +               return -ENODEV;
> +
> +       /* Filter out flags not applicable to multifunction */
> +       acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
> +
> +       return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
> +}
> +
>  static const struct pci_dev_acs_enabled {
>         u16 vendor;
>         u16 device;
>         int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
>  } pci_dev_acs_enabled[] = {
> +       /*
> +        * AMD/ATI multifunction southbridge devices.  AMD has confirmed
> +        * that peer-to-peer between these devices is not possible, so
> +        * they do support a subset of ACS even though the capability is
> +        * not exposed in config space.
> +        */
> +       { PCI_VENDOR_ID_ATI, 0x4385, pci_mf_no_p2p_acs_enabled },
> +       { PCI_VENDOR_ID_ATI, 0x439c, pci_mf_no_p2p_acs_enabled },
> +       { PCI_VENDOR_ID_ATI, 0x4383, pci_mf_no_p2p_acs_enabled },
> +       { PCI_VENDOR_ID_ATI, 0x439d, pci_mf_no_p2p_acs_enabled },
> +       { PCI_VENDOR_ID_ATI, 0x4384, pci_mf_no_p2p_acs_enabled },
> +       { PCI_VENDOR_ID_ATI, 0x4399, pci_mf_no_p2p_acs_enabled },
>         { 0 }
>  };
>
>

I was looking for something else and found this old email.  This patch
hasn't been applied and I haven't seen any discussion about it.  Is it
still of interest?  It seems relevant to the current ACS discussion
[1].

If it's relevant, what's the topology?  Apparently they don't have a
PCIe capability.  Is the upstream device a PCIe device (a downstream
port or a root port)?  I assume anything downstream from these AMD
devices (0x4385, 0x439c, etc.) is plain PCI (not PCIe)?

Bjorn

[1] https://lkml.kernel.org/r/20130607163441.7733.23221.stgit@bling.home
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Bjorn Helgaas June 26, 2013, 4:22 a.m. UTC | #3 
[fix Joerg's email address]

On Tue, Jun 25, 2013 at 10:15 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> On Wed, Jul 11, 2012 at 11:18 PM, Alex Williamson
> <alex.williamson@redhat.com> wrote:
>> We've confirmed that peer-to-peer between these devices is
>> not possible.  We can therefore claim that they support a
>> subset of ACS.
>>
>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
>> Cc: Joerg Roedel <Joerg.Roedel@amd.com>
>> ---
>>
>> Two things about this patch make me a little nervous.  The
>> first is that I'd really like to have a pci_is_pcie() test
>> in pci_mf_no_p2p_acs_enabled(), but these devices don't
>> have a PCIe capability.  That means that if there was a
>> topology where these devices sit on a legacy PCI bus,
>> we incorrectly return that we're ACS safe here.  That leads
>> to my second problem, pciids seems to suggest that some of
>> these functions have been around for a while.  Is it just
>> this package that's peer-to-peer safe, or is it safe to
>> assume that any previous assembly of these functions is
>> also p2p safe.  Maybe we need to factor in device revs if
>> that uniquely identifies this package?
>>
>> Looks like another useful device to potentially quirk
>> would be:
>>
>> 00:15.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 0)
>> 00:15.1 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 1)
>> 00:15.2 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 2)
>> 00:15.3 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 3)
>>
>> 00:15.0 0604: 1002:43a0
>> 00:15.1 0604: 1002:43a1
>> 00:15.2 0604: 1002:43a2
>> 00:15.3 0604: 1002:43a3
>>
>>  drivers/pci/quirks.c |   29 +++++++++++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>> index 4ebc865..2c84961 100644
>> --- a/drivers/pci/quirks.c
>> +++ b/drivers/pci/quirks.c
>> @@ -3271,11 +3271,40 @@ struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
>>         return pci_dev_get(dev);
>>  }
>>
>> +/*
>> + * Multifunction devices that do not support peer-to-peer between
>> + * functions can claim to support a subset of ACS.  Such devices
>> + * effectively enable request redirect (RR) and completion redirect (CR)
>> + * since all transactions are redirected to the upstream root complex.
>> + */
>> +static int pci_mf_no_p2p_acs_enabled(struct pci_dev *dev, u16 acs_flags)
>> +{
>> +       if (!dev->multifunction)
>> +               return -ENODEV;
>> +
>> +       /* Filter out flags not applicable to multifunction */
>> +       acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
>> +
>> +       return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
>> +}
>> +
>>  static const struct pci_dev_acs_enabled {
>>         u16 vendor;
>>         u16 device;
>>         int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
>>  } pci_dev_acs_enabled[] = {
>> +       /*
>> +        * AMD/ATI multifunction southbridge devices.  AMD has confirmed
>> +        * that peer-to-peer between these devices is not possible, so
>> +        * they do support a subset of ACS even though the capability is
>> +        * not exposed in config space.
>> +        */
>> +       { PCI_VENDOR_ID_ATI, 0x4385, pci_mf_no_p2p_acs_enabled },
>> +       { PCI_VENDOR_ID_ATI, 0x439c, pci_mf_no_p2p_acs_enabled },
>> +       { PCI_VENDOR_ID_ATI, 0x4383, pci_mf_no_p2p_acs_enabled },
>> +       { PCI_VENDOR_ID_ATI, 0x439d, pci_mf_no_p2p_acs_enabled },
>> +       { PCI_VENDOR_ID_ATI, 0x4384, pci_mf_no_p2p_acs_enabled },
>> +       { PCI_VENDOR_ID_ATI, 0x4399, pci_mf_no_p2p_acs_enabled },
>>         { 0 }
>>  };
>>
>>
>
> I was looking for something else and found this old email.  This patch
> hasn't been applied and I haven't seen any discussion about it.  Is it
> still of interest?  It seems relevant to the current ACS discussion
> [1].
>
> If it's relevant, what's the topology?  Apparently they don't have a
> PCIe capability.  Is the upstream device a PCIe device (a downstream
> port or a root port)?  I assume anything downstream from these AMD
> devices (0x4385, 0x439c, etc.) is plain PCI (not PCIe)?
>
> Bjorn
>
> [1] https://lkml.kernel.org/r/20130607163441.7733.23221.stgit@bling.home
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Andreas Hartmann June 26, 2013, 3:14 p.m. UTC | #4 
Bjorn Helgaas wrote:
> [fix Joerg's email address]
> 
> On Tue, Jun 25, 2013 at 10:15 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
>> On Wed, Jul 11, 2012 at 11:18 PM, Alex Williamson
>> <alex.williamson@redhat.com> wrote:
>>> We've confirmed that peer-to-peer between these devices is
>>> not possible.  We can therefore claim that they support a
>>> subset of ACS.
>>>
>>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
>>> Cc: Joerg Roedel <Joerg.Roedel@amd.com>
>>> ---
>>>
>>> Two things about this patch make me a little nervous.  The
>>> first is that I'd really like to have a pci_is_pcie() test
>>> in pci_mf_no_p2p_acs_enabled(), but these devices don't
>>> have a PCIe capability.  That means that if there was a
>>> topology where these devices sit on a legacy PCI bus,
>>> we incorrectly return that we're ACS safe here.  That leads
>>> to my second problem, pciids seems to suggest that some of
>>> these functions have been around for a while.  Is it just
>>> this package that's peer-to-peer safe, or is it safe to
>>> assume that any previous assembly of these functions is
>>> also p2p safe.  Maybe we need to factor in device revs if
>>> that uniquely identifies this package?
>>>
>>> Looks like another useful device to potentially quirk
>>> would be:
>>>
>>> 00:15.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 0)
>>> 00:15.1 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 1)
>>> 00:15.2 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 2)
>>> 00:15.3 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 3)
>>>
>>> 00:15.0 0604: 1002:43a0
>>> 00:15.1 0604: 1002:43a1
>>> 00:15.2 0604: 1002:43a2
>>> 00:15.3 0604: 1002:43a3
>>>
>>>  drivers/pci/quirks.c |   29 +++++++++++++++++++++++++++++
>>>  1 file changed, 29 insertions(+)
>>>
>>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>>> index 4ebc865..2c84961 100644
>>> --- a/drivers/pci/quirks.c
>>> +++ b/drivers/pci/quirks.c
>>> @@ -3271,11 +3271,40 @@ struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
>>>         return pci_dev_get(dev);
>>>  }
>>>
>>> +/*
>>> + * Multifunction devices that do not support peer-to-peer between
>>> + * functions can claim to support a subset of ACS.  Such devices
>>> + * effectively enable request redirect (RR) and completion redirect (CR)
>>> + * since all transactions are redirected to the upstream root complex.
>>> + */
>>> +static int pci_mf_no_p2p_acs_enabled(struct pci_dev *dev, u16 acs_flags)
>>> +{
>>> +       if (!dev->multifunction)
>>> +               return -ENODEV;
>>> +
>>> +       /* Filter out flags not applicable to multifunction */
>>> +       acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
>>> +
>>> +       return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
>>> +}
>>> +
>>>  static const struct pci_dev_acs_enabled {
>>>         u16 vendor;
>>>         u16 device;
>>>         int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
>>>  } pci_dev_acs_enabled[] = {
>>> +       /*
>>> +        * AMD/ATI multifunction southbridge devices.  AMD has confirmed
>>> +        * that peer-to-peer between these devices is not possible, so
>>> +        * they do support a subset of ACS even though the capability is
>>> +        * not exposed in config space.
>>> +        */
>>> +       { PCI_VENDOR_ID_ATI, 0x4385, pci_mf_no_p2p_acs_enabled },
>>> +       { PCI_VENDOR_ID_ATI, 0x439c, pci_mf_no_p2p_acs_enabled },
>>> +       { PCI_VENDOR_ID_ATI, 0x4383, pci_mf_no_p2p_acs_enabled },
>>> +       { PCI_VENDOR_ID_ATI, 0x439d, pci_mf_no_p2p_acs_enabled },
>>> +       { PCI_VENDOR_ID_ATI, 0x4384, pci_mf_no_p2p_acs_enabled },
>>> +       { PCI_VENDOR_ID_ATI, 0x4399, pci_mf_no_p2p_acs_enabled },
>>>         { 0 }
>>>  };
>>>
>>>
>>
>> I was looking for something else and found this old email.  This patch
>> hasn't been applied and I haven't seen any discussion about it.  Is it
>> still of interest?  It seems relevant to the current ACS discussion
>> [1].

It is absolutely relevant. I always have to patch my kernel to get it
working to put my pci device to VM. Meanwhile I'm doing it for
kernel 3.9. I would be very glad to get these patches to the kernel as
they don't do anything bad!

My multifunction devices are the devices defined in the patch. My
current pci device passed through is a intel ethernet device:

-[0000:00]-+-00.0  Advanced Micro Devices [AMD] nee ATI RD890 PCI to PCI bridge (external gfx0 port B)
           +-00.2  Advanced Micro Devices [AMD] nee ATI RD990 I/O Memory Management Unit (IOMMU)
           +-02.0-[01]--+-00.0  Advanced Micro Devices [AMD] nee ATI Turks [Radeon HD 6570]
           |            \-00.1  Advanced Micro Devices [AMD] nee ATI Turks HDMI Audio [Radeon HD 6000 Series]
           +-04.0-[02]----00.0  Etron Technology, Inc. EJ168 USB 3.0 Host Controller
           +-05.0-[03]----00.0  Atheros Communications Inc. AR9300 Wireless LAN adaptor
           +-09.0-[04]----00.0  Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller
           +-0a.0-[05]----00.0  Etron Technology, Inc. EJ168 USB 3.0 Host Controller
           +-11.0  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 SATA Controller [AHCI mode]
           +-12.0  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
           +-12.2  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 USB EHCI Controller
           +-13.0  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
           +-13.2  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 USB EHCI Controller
           +-14.0  Advanced Micro Devices [AMD] nee ATI SBx00 SMBus Controller
           +-14.2  Advanced Micro Devices [AMD] nee ATI SBx00 Azalia (Intel HDA)
           +-14.3  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 LPC host controller
           +-14.4-[06]--+-06.0  Intel Corporation 82557/8/9/0/1 Ethernet Pro 100
           |            \-0e.0  VIA Technologies, Inc. VT6306/7/8 [Fire II(M)] IEEE 1394 OHCI Controller
           +-14.5  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 USB OHCI2 Controller
           +-15.0-[07]--
           +-16.0  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
           +-16.2  Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 USB EHCI Controller
           +-18.0  Advanced Micro Devices [AMD] Family 15h Processor Function 0
           +-18.1  Advanced Micro Devices [AMD] Family 15h Processor Function 1
           +-18.2  Advanced Micro Devices [AMD] Family 15h Processor Function 2
           +-18.3  Advanced Micro Devices [AMD] Family 15h Processor Function 3
           +-18.4  Advanced Micro Devices [AMD] Family 15h Processor Function 4
           \-18.5  Advanced Micro Devices [AMD] Family 15h Processor Function 5


lspci -vvvvv -s 14.4
00:14.4 PCI bridge: Advanced Micro Devices [AMD] nee ATI SBx00 PCI to PCI Bridge (rev 40) (prog-if 01 [Subtractive decode])
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop+ ParErr- Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 64
        Bus: primary=00, secondary=06, subordinate=06, sec-latency=64
        I/O behind bridge: 00009000-00009fff
        Memory behind bridge: fd800000-fd8fffff
        Prefetchable memory behind bridge: fd700000-fd7fffff
        Secondary status: 66MHz- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort+ <SERR- <PERR-
        BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B-
                PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-


lspci -vvvvv -s 6.0
06:06.0 Ethernet controller: Intel Corporation 82557/8/9/0/1 Ethernet Pro 100 (rev 0c)
        Subsystem: Intel Corporation EtherExpress PRO/100 S Desktop Adapter
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 64 (2000ns min, 14000ns max), Cache Line Size: 64 bytes
        Interrupt: pin A routed to IRQ 20
        Region 0: Memory at fd8ff000 (32-bit, non-prefetchable) [size=4K]
        Region 1: I/O ports at 9f00 [size=64]
        Region 2: Memory at fd8c0000 (32-bit, non-prefetchable) [size=128K]
        Expansion ROM at fd700000 [disabled] [size=64K]
        Capabilities: [dc] Power Management version 2
                Flags: PMEClk- DSI+ D1+ D2+ AuxCurrent=0mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
                Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=2 PME-
        Kernel driver in use: vfio-pci


Thanks,
kind regards,
Andreas Hartmann
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Alex Williamson June 26, 2013, 3:51 p.m. UTC | #5 
On Wed, 2013-06-26 at 17:14 +0200, Andreas Hartmann wrote:
> Bjorn Helgaas wrote:
> > [fix Joerg's email address]
> > 
> > On Tue, Jun 25, 2013 at 10:15 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> >> On Wed, Jul 11, 2012 at 11:18 PM, Alex Williamson
> >> <alex.williamson@redhat.com> wrote:
> >>> We've confirmed that peer-to-peer between these devices is
> >>> not possible.  We can therefore claim that they support a
> >>> subset of ACS.
> >>>
> >>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> >>> Cc: Joerg Roedel <Joerg.Roedel@amd.com>
> >>> ---
> >>>
> >>> Two things about this patch make me a little nervous.  The
> >>> first is that I'd really like to have a pci_is_pcie() test
> >>> in pci_mf_no_p2p_acs_enabled(), but these devices don't
> >>> have a PCIe capability.  That means that if there was a
> >>> topology where these devices sit on a legacy PCI bus,
> >>> we incorrectly return that we're ACS safe here.  That leads
> >>> to my second problem, pciids seems to suggest that some of
> >>> these functions have been around for a while.  Is it just
> >>> this package that's peer-to-peer safe, or is it safe to
> >>> assume that any previous assembly of these functions is
> >>> also p2p safe.  Maybe we need to factor in device revs if
> >>> that uniquely identifies this package?
> >>>
> >>> Looks like another useful device to potentially quirk
> >>> would be:
> >>>
> >>> 00:15.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 0)
> >>> 00:15.1 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 1)
> >>> 00:15.2 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 2)
> >>> 00:15.3 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 3)
> >>>
> >>> 00:15.0 0604: 1002:43a0
> >>> 00:15.1 0604: 1002:43a1
> >>> 00:15.2 0604: 1002:43a2
> >>> 00:15.3 0604: 1002:43a3
> >>>
> >>>  drivers/pci/quirks.c |   29 +++++++++++++++++++++++++++++
> >>>  1 file changed, 29 insertions(+)
> >>>
> >>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> >>> index 4ebc865..2c84961 100644
> >>> --- a/drivers/pci/quirks.c
> >>> +++ b/drivers/pci/quirks.c
> >>> @@ -3271,11 +3271,40 @@ struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
> >>>         return pci_dev_get(dev);
> >>>  }
> >>>
> >>> +/*
> >>> + * Multifunction devices that do not support peer-to-peer between
> >>> + * functions can claim to support a subset of ACS.  Such devices
> >>> + * effectively enable request redirect (RR) and completion redirect (CR)
> >>> + * since all transactions are redirected to the upstream root complex.
> >>> + */
> >>> +static int pci_mf_no_p2p_acs_enabled(struct pci_dev *dev, u16 acs_flags)
> >>> +{
> >>> +       if (!dev->multifunction)
> >>> +               return -ENODEV;
> >>> +
> >>> +       /* Filter out flags not applicable to multifunction */
> >>> +       acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
> >>> +
> >>> +       return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
> >>> +}
> >>> +
> >>>  static const struct pci_dev_acs_enabled {
> >>>         u16 vendor;
> >>>         u16 device;
> >>>         int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
> >>>  } pci_dev_acs_enabled[] = {
> >>> +       /*
> >>> +        * AMD/ATI multifunction southbridge devices.  AMD has confirmed
> >>> +        * that peer-to-peer between these devices is not possible, so
> >>> +        * they do support a subset of ACS even though the capability is
> >>> +        * not exposed in config space.
> >>> +        */
> >>> +       { PCI_VENDOR_ID_ATI, 0x4385, pci_mf_no_p2p_acs_enabled },
> >>> +       { PCI_VENDOR_ID_ATI, 0x439c, pci_mf_no_p2p_acs_enabled },
> >>> +       { PCI_VENDOR_ID_ATI, 0x4383, pci_mf_no_p2p_acs_enabled },
> >>> +       { PCI_VENDOR_ID_ATI, 0x439d, pci_mf_no_p2p_acs_enabled },
> >>> +       { PCI_VENDOR_ID_ATI, 0x4384, pci_mf_no_p2p_acs_enabled },
> >>> +       { PCI_VENDOR_ID_ATI, 0x4399, pci_mf_no_p2p_acs_enabled },
> >>>         { 0 }
> >>>  };
> >>>
> >>>
> >>
> >> I was looking for something else and found this old email.  This patch
> >> hasn't been applied and I haven't seen any discussion about it.  Is it
> >> still of interest?  It seems relevant to the current ACS discussion
> >> [1].
> 
> It is absolutely relevant. I always have to patch my kernel to get it
> working to put my pci device to VM. Meanwhile I'm doing it for
> kernel 3.9. I would be very glad to get these patches to the kernel as
> they don't do anything bad!

I'd still like to see this get in too.  IIRC, where we left off was that
Joerg had confirmed with the hardware folks that there is no
peer-to-peer between these devices, but we still had questions about
whether that was true for any instance of these vendor/device IDs.
These devices are re-used in several packages and I'm not sure if we
need to somehow figure out what package (ie. which chipset generation)
we're looking at to know if p2p is used.  Thanks,

Alex


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Andreas Hartmann June 26, 2013, 4:24 p.m. UTC | #6 
Alex Williamson wrote:
> On Wed, 2013-06-26 at 17:14 +0200, Andreas Hartmann wrote:
>> Bjorn Helgaas wrote:
>>> [fix Joerg's email address]
>>>
>>> On Tue, Jun 25, 2013 at 10:15 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
>>>> On Wed, Jul 11, 2012 at 11:18 PM, Alex Williamson
>>>> <alex.williamson@redhat.com> wrote:
>>>>> We've confirmed that peer-to-peer between these devices is
>>>>> not possible.  We can therefore claim that they support a
>>>>> subset of ACS.
>>>>>
>>>>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
>>>>> Cc: Joerg Roedel <Joerg.Roedel@amd.com>
>>>>> ---
>>>>>
>>>>> Two things about this patch make me a little nervous.  The
>>>>> first is that I'd really like to have a pci_is_pcie() test
>>>>> in pci_mf_no_p2p_acs_enabled(), but these devices don't
>>>>> have a PCIe capability.  That means that if there was a
>>>>> topology where these devices sit on a legacy PCI bus,
>>>>> we incorrectly return that we're ACS safe here.  That leads
>>>>> to my second problem, pciids seems to suggest that some of
>>>>> these functions have been around for a while.  Is it just
>>>>> this package that's peer-to-peer safe, or is it safe to
>>>>> assume that any previous assembly of these functions is
>>>>> also p2p safe.  Maybe we need to factor in device revs if
>>>>> that uniquely identifies this package?
>>>>>
>>>>> Looks like another useful device to potentially quirk
>>>>> would be:
>>>>>
>>>>> 00:15.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 0)
>>>>> 00:15.1 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 1)
>>>>> 00:15.2 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 2)
>>>>> 00:15.3 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 3)
>>>>>
>>>>> 00:15.0 0604: 1002:43a0
>>>>> 00:15.1 0604: 1002:43a1
>>>>> 00:15.2 0604: 1002:43a2
>>>>> 00:15.3 0604: 1002:43a3
>>>>>
>>>>>  drivers/pci/quirks.c |   29 +++++++++++++++++++++++++++++
>>>>>  1 file changed, 29 insertions(+)
>>>>>
>>>>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>>>>> index 4ebc865..2c84961 100644
>>>>> --- a/drivers/pci/quirks.c
>>>>> +++ b/drivers/pci/quirks.c
>>>>> @@ -3271,11 +3271,40 @@ struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
>>>>>         return pci_dev_get(dev);
>>>>>  }
>>>>>
>>>>> +/*
>>>>> + * Multifunction devices that do not support peer-to-peer between
>>>>> + * functions can claim to support a subset of ACS.  Such devices
>>>>> + * effectively enable request redirect (RR) and completion redirect (CR)
>>>>> + * since all transactions are redirected to the upstream root complex.
>>>>> + */
>>>>> +static int pci_mf_no_p2p_acs_enabled(struct pci_dev *dev, u16 acs_flags)
>>>>> +{
>>>>> +       if (!dev->multifunction)
>>>>> +               return -ENODEV;
>>>>> +
>>>>> +       /* Filter out flags not applicable to multifunction */
>>>>> +       acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
>>>>> +
>>>>> +       return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
>>>>> +}
>>>>> +
>>>>>  static const struct pci_dev_acs_enabled {
>>>>>         u16 vendor;
>>>>>         u16 device;
>>>>>         int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
>>>>>  } pci_dev_acs_enabled[] = {
>>>>> +       /*
>>>>> +        * AMD/ATI multifunction southbridge devices.  AMD has confirmed
>>>>> +        * that peer-to-peer between these devices is not possible, so
>>>>> +        * they do support a subset of ACS even though the capability is
>>>>> +        * not exposed in config space.
>>>>> +        */
>>>>> +       { PCI_VENDOR_ID_ATI, 0x4385, pci_mf_no_p2p_acs_enabled },
>>>>> +       { PCI_VENDOR_ID_ATI, 0x439c, pci_mf_no_p2p_acs_enabled },
>>>>> +       { PCI_VENDOR_ID_ATI, 0x4383, pci_mf_no_p2p_acs_enabled },
>>>>> +       { PCI_VENDOR_ID_ATI, 0x439d, pci_mf_no_p2p_acs_enabled },
>>>>> +       { PCI_VENDOR_ID_ATI, 0x4384, pci_mf_no_p2p_acs_enabled },
>>>>> +       { PCI_VENDOR_ID_ATI, 0x4399, pci_mf_no_p2p_acs_enabled },
>>>>>         { 0 }
>>>>>  };
>>>>>
>>>>>
>>>>
>>>> I was looking for something else and found this old email.  This patch
>>>> hasn't been applied and I haven't seen any discussion about it.  Is it
>>>> still of interest?  It seems relevant to the current ACS discussion
>>>> [1].
>>
>> It is absolutely relevant. I always have to patch my kernel to get it
>> working to put my pci device to VM. Meanwhile I'm doing it for
>> kernel 3.9. I would be very glad to get these patches to the kernel as
>> they don't do anything bad!
> 
> I'd still like to see this get in too.  IIRC, where we left off was that
> Joerg had confirmed with the hardware folks that there is no
> peer-to-peer between these devices, but we still had questions about
> whether that was true for any instance of these vendor/device IDs.
> These devices are re-used in several packages and I'm not sure if we
> need to somehow figure out what package (ie. which chipset generation)
> we're looking at to know if p2p is used. 

Does this statement cover your question?
http://article.gmane.org/gmane.comp.emulators.kvm.devel/99402

Andreas
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Alex Williamson June 26, 2013, 4:44 p.m. UTC | #7 
On Wed, 2013-06-26 at 18:24 +0200, Andreas Hartmann wrote:
> Alex Williamson wrote:
> > On Wed, 2013-06-26 at 17:14 +0200, Andreas Hartmann wrote:
> >> Bjorn Helgaas wrote:
> >>> [fix Joerg's email address]
> >>>
> >>> On Tue, Jun 25, 2013 at 10:15 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> >>>> On Wed, Jul 11, 2012 at 11:18 PM, Alex Williamson
> >>>> <alex.williamson@redhat.com> wrote:
> >>>>> We've confirmed that peer-to-peer between these devices is
> >>>>> not possible.  We can therefore claim that they support a
> >>>>> subset of ACS.
> >>>>>
> >>>>> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> >>>>> Cc: Joerg Roedel <Joerg.Roedel@amd.com>
> >>>>> ---
> >>>>>
> >>>>> Two things about this patch make me a little nervous.  The
> >>>>> first is that I'd really like to have a pci_is_pcie() test
> >>>>> in pci_mf_no_p2p_acs_enabled(), but these devices don't
> >>>>> have a PCIe capability.  That means that if there was a
> >>>>> topology where these devices sit on a legacy PCI bus,
> >>>>> we incorrectly return that we're ACS safe here.  That leads
> >>>>> to my second problem, pciids seems to suggest that some of
> >>>>> these functions have been around for a while.  Is it just
> >>>>> this package that's peer-to-peer safe, or is it safe to
> >>>>> assume that any previous assembly of these functions is
> >>>>> also p2p safe.  Maybe we need to factor in device revs if
> >>>>> that uniquely identifies this package?
> >>>>>
> >>>>> Looks like another useful device to potentially quirk
> >>>>> would be:
> >>>>>
> >>>>> 00:15.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 0)
> >>>>> 00:15.1 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB700/SB800/SB900 PCI to PCI bridge (PCIE port 1)
> >>>>> 00:15.2 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 2)
> >>>>> 00:15.3 PCI bridge: Advanced Micro Devices [AMD] nee ATI SB900 PCI to PCI bridge (PCIE port 3)
> >>>>>
> >>>>> 00:15.0 0604: 1002:43a0
> >>>>> 00:15.1 0604: 1002:43a1
> >>>>> 00:15.2 0604: 1002:43a2
> >>>>> 00:15.3 0604: 1002:43a3
> >>>>>
> >>>>>  drivers/pci/quirks.c |   29 +++++++++++++++++++++++++++++
> >>>>>  1 file changed, 29 insertions(+)
> >>>>>
> >>>>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> >>>>> index 4ebc865..2c84961 100644
> >>>>> --- a/drivers/pci/quirks.c
> >>>>> +++ b/drivers/pci/quirks.c
> >>>>> @@ -3271,11 +3271,40 @@ struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
> >>>>>         return pci_dev_get(dev);
> >>>>>  }
> >>>>>
> >>>>> +/*
> >>>>> + * Multifunction devices that do not support peer-to-peer between
> >>>>> + * functions can claim to support a subset of ACS.  Such devices
> >>>>> + * effectively enable request redirect (RR) and completion redirect (CR)
> >>>>> + * since all transactions are redirected to the upstream root complex.
> >>>>> + */
> >>>>> +static int pci_mf_no_p2p_acs_enabled(struct pci_dev *dev, u16 acs_flags)
> >>>>> +{
> >>>>> +       if (!dev->multifunction)
> >>>>> +               return -ENODEV;
> >>>>> +
> >>>>> +       /* Filter out flags not applicable to multifunction */
> >>>>> +       acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
> >>>>> +
> >>>>> +       return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
> >>>>> +}
> >>>>> +
> >>>>>  static const struct pci_dev_acs_enabled {
> >>>>>         u16 vendor;
> >>>>>         u16 device;
> >>>>>         int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
> >>>>>  } pci_dev_acs_enabled[] = {
> >>>>> +       /*
> >>>>> +        * AMD/ATI multifunction southbridge devices.  AMD has confirmed
> >>>>> +        * that peer-to-peer between these devices is not possible, so
> >>>>> +        * they do support a subset of ACS even though the capability is
> >>>>> +        * not exposed in config space.
> >>>>> +        */
> >>>>> +       { PCI_VENDOR_ID_ATI, 0x4385, pci_mf_no_p2p_acs_enabled },
> >>>>> +       { PCI_VENDOR_ID_ATI, 0x439c, pci_mf_no_p2p_acs_enabled },
> >>>>> +       { PCI_VENDOR_ID_ATI, 0x4383, pci_mf_no_p2p_acs_enabled },
> >>>>> +       { PCI_VENDOR_ID_ATI, 0x439d, pci_mf_no_p2p_acs_enabled },
> >>>>> +       { PCI_VENDOR_ID_ATI, 0x4384, pci_mf_no_p2p_acs_enabled },
> >>>>> +       { PCI_VENDOR_ID_ATI, 0x4399, pci_mf_no_p2p_acs_enabled },
> >>>>>         { 0 }
> >>>>>  };
> >>>>>
> >>>>>
> >>>>
> >>>> I was looking for something else and found this old email.  This patch
> >>>> hasn't been applied and I haven't seen any discussion about it.  Is it
> >>>> still of interest?  It seems relevant to the current ACS discussion
> >>>> [1].
> >>
> >> It is absolutely relevant. I always have to patch my kernel to get it
> >> working to put my pci device to VM. Meanwhile I'm doing it for
> >> kernel 3.9. I would be very glad to get these patches to the kernel as
> >> they don't do anything bad!
> > 
> > I'd still like to see this get in too.  IIRC, where we left off was that
> > Joerg had confirmed with the hardware folks that there is no
> > peer-to-peer between these devices, but we still had questions about
> > whether that was true for any instance of these vendor/device IDs.
> > These devices are re-used in several packages and I'm not sure if we
> > need to somehow figure out what package (ie. which chipset generation)
> > we're looking at to know if p2p is used. 
> 
> Does this statement cover your question?
> http://article.gmane.org/gmane.comp.emulators.kvm.devel/99402

Yeah, perhaps it does.  I initially disregarded it because it's easy to
tell if an IOMMU is active, but more difficult to tell if one is there
and inactive.  However, iommu_present() will tell us if one is there and
active, which is mostly what we care about.  Thanks,

Alex


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diff mbox

Patch

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 4ebc865..2c84961 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -3271,11 +3271,40 @@  struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
 	return pci_dev_get(dev);
 }
 
+/*
+ * Multifunction devices that do not support peer-to-peer between
+ * functions can claim to support a subset of ACS.  Such devices
+ * effectively enable request redirect (RR) and completion redirect (CR)
+ * since all transactions are redirected to the upstream root complex.
+ */
+static int pci_mf_no_p2p_acs_enabled(struct pci_dev *dev, u16 acs_flags)
+{
+	if (!dev->multifunction)
+		return -ENODEV;
+
+	/* Filter out flags not applicable to multifunction */
+	acs_flags &= (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC | PCI_ACS_DT);
+
+	return acs_flags & ~(PCI_ACS_RR | PCI_ACS_CR) ? 0 : 1;
+}
+
 static const struct pci_dev_acs_enabled {
 	u16 vendor;
 	u16 device;
 	int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags);
 } pci_dev_acs_enabled[] = {
+	/*
+	 * AMD/ATI multifunction southbridge devices.  AMD has confirmed
+	 * that peer-to-peer between these devices is not possible, so
+	 * they do support a subset of ACS even though the capability is
+	 * not exposed in config space.
+	 */
+	{ PCI_VENDOR_ID_ATI, 0x4385, pci_mf_no_p2p_acs_enabled },
+	{ PCI_VENDOR_ID_ATI, 0x439c, pci_mf_no_p2p_acs_enabled },
+	{ PCI_VENDOR_ID_ATI, 0x4383, pci_mf_no_p2p_acs_enabled },
+	{ PCI_VENDOR_ID_ATI, 0x439d, pci_mf_no_p2p_acs_enabled },
+	{ PCI_VENDOR_ID_ATI, 0x4384, pci_mf_no_p2p_acs_enabled },
+	{ PCI_VENDOR_ID_ATI, 0x4399, pci_mf_no_p2p_acs_enabled },
 	{ 0 }
 };