| Message ID | 20230707014754.51333-2-stewart.hildebrand@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Kconfig for PCI passthrough on ARM | expand |
On 07.07.2023 03:47, Stewart Hildebrand wrote: > --- a/xen/arch/arm/Kconfig > +++ b/xen/arch/arm/Kconfig > @@ -190,6 +190,15 @@ config STATIC_SHM > help > This option enables statically shared memory on a dom0less system. > > +config PCI_PASSTHROUGH > + bool "PCI passthrough" if EXPERT > + depends on ARM_64 > + select HAS_PCI > + select HAS_VPCI > + default n No need for this line - that's what the tool does by default anyway. Jan
Hi Jan, On 07/07/2023 07:55, Jan Beulich wrote: > On 07.07.2023 03:47, Stewart Hildebrand wrote: >> --- a/xen/arch/arm/Kconfig >> +++ b/xen/arch/arm/Kconfig >> @@ -190,6 +190,15 @@ config STATIC_SHM >> help >> This option enables statically shared memory on a dom0less system. >> >> +config PCI_PASSTHROUGH >> + bool "PCI passthrough" if EXPERT >> + depends on ARM_64 >> + select HAS_PCI >> + select HAS_VPCI >> + default n > > No need for this line - that's what the tool does by default anyway. I would rather keep. We are already using 'default n' and it is making more obvious the default value. Cheers,
Hi, On 07/07/2023 02:47, Stewart Hildebrand wrote: > From: Rahul Singh <rahul.singh@arm.com> > > Setting CONFIG_PCI_PASSTHROUGH=y will enable PCI passthrough on ARM, even though > the feature is not yet complete in the current upstream codebase. The purpose of > this is to make it easier to enable the necessary configs (HAS_PCI, HAS_VPCI) for > testing and development of PCI passthrough on ARM. > > Since PCI passthrough on ARM is still work in progress at this time, make it > depend on EXPERT. > > Signed-off-by: Rahul Singh <rahul.singh@arm.com> > Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com> > Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com> Acked-by: Julien Grall <jgrall@amazon.com> Cheers,
Hi Stewart, On 07/07/2023 02:47, Stewart Hildebrand wrote: > From: Rahul Singh <rahul.singh@arm.com> > > Setting CONFIG_PCI_PASSTHROUGH=y will enable PCI passthrough on ARM, even though > the feature is not yet complete in the current upstream codebase. The purpose of > this is to make it easier to enable the necessary configs (HAS_PCI, HAS_VPCI) for > testing and development of PCI passthrough on ARM. > > Since PCI passthrough on ARM is still work in progress at this time, make it > depend on EXPERT. While preparing the patch for committing, I noticed that HAS_PASSTHROUGH will now allow the user to select one of the IOMMU quarantine options. There are three of them right now: 1. none 2. basic (i.e. faulting) 3. scratch page The latter is unlikely to work on Arm because we don't setup the scratch page. AFAIU, for that, we would need to implement the callback quarantine_init(). I would expect 1 and 2 work. That said, I think 1. would behave like 2. because on Arm the device should not be automatically re-assigned to dom0. I know this is correct for platform device, but will it be valid for PCI as well? Overall, before enabling HAS_PASSTHROUGH, I think there would be a bit of tweaking necessary to at least prevent a user to select the option 3 (either via Kconfig or the command line). And possibly update the Kconfig for IOMMU_QUARANTINE to reflect the behavior on Arm. Cheers,
On 7/13/23 14:40, Julien Grall wrote: > Hi Stewart, > > On 07/07/2023 02:47, Stewart Hildebrand wrote: >> From: Rahul Singh <rahul.singh@arm.com> >> >> Setting CONFIG_PCI_PASSTHROUGH=y will enable PCI passthrough on ARM, even though >> the feature is not yet complete in the current upstream codebase. The purpose of >> this is to make it easier to enable the necessary configs (HAS_PCI, HAS_VPCI) for >> testing and development of PCI passthrough on ARM. >> >> Since PCI passthrough on ARM is still work in progress at this time, make it >> depend on EXPERT. > > While preparing the patch for committing, I noticed that HAS_PASSTHROUGH > will now allow the user to select one of the IOMMU quarantine options. > > There are three of them right now: > 1. none > 2. basic (i.e. faulting) > 3. scratch page > > The latter is unlikely to work on Arm because we don't setup the scratch > page. AFAIU, for that, we would need to implement the callback > quarantine_init(). > > I would expect 1 and 2 work. That said, I think 1. would behave like 2. > because on Arm the device should not be automatically re-assigned to > dom0. I know this is correct for platform device, but will it be valid > for PCI as well? In a system with dom0 where the guest is created from the xl toolstack, we rely on "xl pci-assignable-add". Upon domain destruction, the device automatically gets assigned to domIO. However, there's nothing preventing a user from attempting to invoke "xl pci-assignable-remove", which should assign the device back to dom0, but it is not automatic. With dom0less, PCI devices are not deassigned from the domU. > Overall, before enabling HAS_PASSTHROUGH, I think there would be a bit > of tweaking necessary to at least prevent a user to select the option 3 > (either via Kconfig or the command line). And possibly update the > Kconfig for IOMMU_QUARANTINE to reflect the behavior on Arm. OK
Hi, On 18/07/2023 18:35, Stewart Hildebrand wrote: > On 7/13/23 14:40, Julien Grall wrote: >> Hi Stewart, >> >> On 07/07/2023 02:47, Stewart Hildebrand wrote: >>> From: Rahul Singh <rahul.singh@arm.com> >>> >>> Setting CONFIG_PCI_PASSTHROUGH=y will enable PCI passthrough on ARM, even though >>> the feature is not yet complete in the current upstream codebase. The purpose of >>> this is to make it easier to enable the necessary configs (HAS_PCI, HAS_VPCI) for >>> testing and development of PCI passthrough on ARM. >>> >>> Since PCI passthrough on ARM is still work in progress at this time, make it >>> depend on EXPERT. >> >> While preparing the patch for committing, I noticed that HAS_PASSTHROUGH >> will now allow the user to select one of the IOMMU quarantine options. >> >> There are three of them right now: >> 1. none >> 2. basic (i.e. faulting) >> 3. scratch page >> >> The latter is unlikely to work on Arm because we don't setup the scratch >> page. AFAIU, for that, we would need to implement the callback >> quarantine_init(). >> >> I would expect 1 and 2 work. That said, I think 1. would behave like 2. >> because on Arm the device should not be automatically re-assigned to >> dom0. I know this is correct for platform device, but will it be valid >> for PCI as well? > > In a system with dom0 where the guest is created from the xl toolstack, we rely on "xl pci-assignable-add". Upon domain destruction, the device automatically gets assigned to domIO. Ok. To clarify, does this mean any DMA will fault, the same as for platform device? > However, there's nothing preventing a user from attempting to invoke "xl pci-assignable-remove", which should assign the device back to dom0, but it is not automatic. I don't think we want to fully prevent a user to re-assign a device to dom0. But we at least want to avoid re-assigning the device to dom0 by default. After that a user can reset the device before it gets re-assigned to dom0. Cheers,
On 7/20/23 05:20, Julien Grall wrote: > Hi, > > On 18/07/2023 18:35, Stewart Hildebrand wrote: >> On 7/13/23 14:40, Julien Grall wrote: >>> Hi Stewart, >>> >>> On 07/07/2023 02:47, Stewart Hildebrand wrote: >>>> From: Rahul Singh <rahul.singh@arm.com> >>>> >>>> Setting CONFIG_PCI_PASSTHROUGH=y will enable PCI passthrough on ARM, even though >>>> the feature is not yet complete in the current upstream codebase. The purpose of >>>> this is to make it easier to enable the necessary configs (HAS_PCI, HAS_VPCI) for >>>> testing and development of PCI passthrough on ARM. >>>> >>>> Since PCI passthrough on ARM is still work in progress at this time, make it >>>> depend on EXPERT. >>> >>> While preparing the patch for committing, I noticed that HAS_PASSTHROUGH >>> will now allow the user to select one of the IOMMU quarantine options. >>> >>> There are three of them right now: >>> 1. none >>> 2. basic (i.e. faulting) >>> 3. scratch page >>> >>> The latter is unlikely to work on Arm because we don't setup the scratch >>> page. AFAIU, for that, we would need to implement the callback >>> quarantine_init(). >>> >>> I would expect 1 and 2 work. That said, I think 1. would behave like 2. >>> because on Arm the device should not be automatically re-assigned to >>> dom0. I know this is correct for platform device, but will it be valid >>> for PCI as well? >> >> In a system with dom0 where the guest is created from the xl toolstack, we rely on "xl pci-assignable-add". Upon domain destruction, the device automatically gets assigned to domIO. > > Ok. To clarify, does this mean any DMA will fault, the same as for > platform device? Yes, when the PCI device is assigned to domIO, any DMA from the device will produce a SMMU fault. The value of the quarantine= option doesn't change this behavior. >> However, there's nothing preventing a user from attempting to invoke "xl pci-assignable-remove", which should assign the device back to dom0, but it is not automatic. > > I don't think we want to fully prevent a user to re-assign a device to > dom0. But we at least want to avoid re-assigning the device to dom0 by > default. After that a user can reset the device before it gets > re-assigned to dom0. > > Cheers, > > -- > Julien Grall
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig index 439cc94f3344..4e0cc421ad48 100644 --- a/xen/arch/arm/Kconfig +++ b/xen/arch/arm/Kconfig @@ -190,6 +190,15 @@ config STATIC_SHM help This option enables statically shared memory on a dom0less system. +config PCI_PASSTHROUGH + bool "PCI passthrough" if EXPERT + depends on ARM_64 + select HAS_PCI + select HAS_VPCI + default n + help + This option enables PCI device passthrough + endmenu menu "ARM errata workaround via the alternative framework"