| Message ID | 1452841574-2781-2-git-send-email-xyjxie@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, 2016-01-15 at 15:06 +0800, Yongji Xie wrote: > When vfio passthrough a PCI device of which MMIO BARs > are smaller than PAGE_SIZE, guest will not handle the > mmio accesses to the BARs which leads to mmio emulations > in host. > > This is because vfio will not allow to passthrough one > BAR's mmio page which may be shared with other BARs. > > To solve this performance issue, this patch adds a kernel > parameter "pci=resource_page_aligned=on" to enforce > the alignment of all MMIO BARs to be at least PAGE_SIZE, > so that one BAR's mmio page would not be shared with other > BARs. We can also disable it through kernel parameter > "pci=resource_page_aligned=off". > > For the default value of the parameter, we think it should be > arch-independent, so we add a macro > HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED to change it. And we > define this macro to enable this parameter by default on PPC64 > platform which can easily hit this performance issue because > its PAGE_SIZE is 64KB. > > Note that the kernel parameter won't works if kernel doesn't do > resources reallocation. And where do you account for this so that we know whether it's really in effect? > Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com> > --- > Documentation/kernel-parameters.txt | 5 +++++ > arch/powerpc/include/asm/pci.h | 11 +++++++++++ > drivers/pci/pci.c | 35 +++++++++++++++++++++++++++++++++++ > drivers/pci/pci.h | 8 +++++++- > include/linux/pci.h | 4 ++++ > 5 files changed, 62 insertions(+), 1 deletion(-) > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index 742f69d..3f2a7c9 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2857,6 +2857,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > PAGE_SIZE is used as alignment. > PCI-PCI bridge can be specified, if resource > windows need to be expanded. > + resource_page_aligned= Enable/disable enforcing the alignment > + of all PCI devices' memory resources to be > + at least PAGE_SIZE if resources reallocation > + is done by kernel. > + Format: { "on" | "off" } > ecrc= Enable/disable PCIe ECRC (transaction layer > end-to-end CRC checking). > bios: Use BIOS/firmware settings. This is the > diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h > index 3453bd8..2d2b3ef 100644 > --- a/arch/powerpc/include/asm/pci.h > +++ b/arch/powerpc/include/asm/pci.h > @@ -136,6 +136,17 @@ extern pgprot_t pci_phys_mem_access_prot(struct file *file, > unsigned long pfn, > unsigned long size, > pgprot_t prot); > +#ifdef CONFIG_PPC64 > + > +/* For PPC64, We enforce all PCI MMIO BARs to be page aligned > + * by default. This would be helpful to improve performance > + * when we passthrough a PCI device of which BARs are smaller > + * than PAGE_SIZE(64KB). And we can use kernel parameter > + * "pci=resource_page_aligned=off" to disable it. > + */ > +#define HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED 1 > + > +#endif > > #define HAVE_ARCH_PCI_RESOURCE_TO_USER > extern void pci_resource_to_user(const struct pci_dev *dev, int bar, > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 314db8c..7b21238 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -99,6 +99,9 @@ u8 pci_cache_line_size; > */ > unsigned int pcibios_max_latency = 255; > > +bool pci_resources_page_aligned = > + IS_ENABLED(HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED); I don't think this is proper use of IS_ENABLED, which seems to be targeted at CONFIG_ type options. You could define this as that in an arch Kconfig. > + > /* If set, the PCIe ARI capability will not be used. */ > static bool pcie_ari_disabled; > > @@ -4746,6 +4749,35 @@ static ssize_t pci_resource_alignment_store(struct bus_type *bus, > BUS_ATTR(resource_alignment, 0644, pci_resource_alignment_show, > pci_resource_alignment_store); > > +static void pci_resources_get_page_aligned(char *str) > +{ > + if (!strncmp(str, "off", 3)) > + pci_resources_page_aligned = false; > + else if (!strncmp(str, "on", 2)) > + pci_resources_page_aligned = true; > +} "get"? > + > +/* > + * This function checks whether PCI BARs' mmio page will be shared > + * with other BARs. > + */ > +bool pci_resources_share_page(struct pci_dev *dev, int resno) > +{ > + struct resource *res = dev->resource + resno; > + > + if (resource_size(res) >= PAGE_SIZE) > + return false; > + if (pci_resources_page_aligned && !(res->start & ~PAGE_MASK) && > + res->flags & IORESOURCE_MEM) { > + if (res->sibling) > + return (res->sibling->start & ~PAGE_MASK); > + else > + return false; > + } > + return true; > +} > +EXPORT_SYMBOL_GPL(pci_resources_share_page); > + > static int __init pci_resource_alignment_sysfs_init(void) > { > return bus_create_file(&pci_bus_type, > @@ -4859,6 +4891,9 @@ static int __init pci_setup(char *str) > } else if (!strncmp(str, "resource_alignment=", 19)) { > pci_set_resource_alignment_param(str + 19, > strlen(str + 19)); > + } else if (!strncmp(str, "resource_page_aligned=", > + 22)) { > + pci_resources_get_page_aligned(str + 22); Doesn't this seem rather redundant with the option right above it, resource_alignment=? Why not modify that to support syntax where all devices get the same alignment? > } else if (!strncmp(str, "ecrc=", 5)) { > pcie_ecrc_get_policy(str + 5); > } else if (!strncmp(str, "hpiosize=", 9)) { > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index d390fc1..b9b333d 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -312,11 +312,17 @@ static inline resource_size_t pci_resource_alignment(struct pci_dev *dev, > #ifdef CONFIG_PCI_IOV > int resno = res - dev->resource; > > - if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) > + if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) { > + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) > + return PAGE_ALIGN(pci_sriov_resource_alignment(dev, > + resno)); > return pci_sriov_resource_alignment(dev, resno); > + } > #endif > if (dev->class >> 8 == PCI_CLASS_BRIDGE_CARDBUS) > return pci_cardbus_resource_alignment(res); > + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) > + return PAGE_ALIGN(resource_alignment(res)); > return resource_alignment(res); > } Since we already have resource_alignment=, shouldn't we already have the code in place to re-align? > > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 6ae25aa..b640d65 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -1530,6 +1530,10 @@ static inline int pci_get_new_domain_nr(void) { return -ENOSYS; } > (pci_resource_end((dev), (bar)) - \ > pci_resource_start((dev), (bar)) + 1)) > > +extern bool pci_resources_page_aligned; > + > +bool pci_resources_share_page(struct pci_dev *dev, int resno); > + > /* Similar to the helpers above, these manipulate per-pci_dev > * driver-specific data. They are really just a wrapper around > * the generic device structure functions of these calls. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2016/1/29 6:46, Alex Williamson wrote: > On Fri, 2016-01-15 at 15:06 +0800, Yongji Xie wrote: >> When vfio passthrough a PCI device of which MMIO BARs >> are smaller than PAGE_SIZE, guest will not handle the >> mmio accesses to the BARs which leads to mmio emulations >> in host. >> >> This is because vfio will not allow to passthrough one >> BAR's mmio page which may be shared with other BARs. >> >> To solve this performance issue, this patch adds a kernel >> parameter "pci=resource_page_aligned=on" to enforce >> the alignment of all MMIO BARs to be at least PAGE_SIZE, >> so that one BAR's mmio page would not be shared with other >> BARs. We can also disable it through kernel parameter >> "pci=resource_page_aligned=off". >> >> For the default value of the parameter, we think it should be >> arch-independent, so we add a macro >> HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED to change it. And we >> define this macro to enable this parameter by default on PPC64 >> platform which can easily hit this performance issue because >> its PAGE_SIZE is 64KB. >> >> Note that the kernel parameter won't works if kernel doesn't do >> resources reallocation. > And where do you account for this so that we know whether it's really in > effect? We can check the flag PCI_PROBE_ONLY to know whether kernel do resources reallocation. Then we know if the kernel parameter is really in effect. enum { /* Force re-assigning all resources (ignore firmware * setup completely) */ PCI_REASSIGN_ALL_RSRC = 0x00000001, /* Re-assign all bus numbers */ PCI_REASSIGN_ALL_BUS = 0x00000002, /* Do not try to assign, just use existing setup */ ---> PCI_PROBE_ONLY = 0x00000004, And I will add this to commit log. >> Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com> >> --- >> Documentation/kernel-parameters.txt | 5 +++++ >> arch/powerpc/include/asm/pci.h | 11 +++++++++++ >> drivers/pci/pci.c | 35 +++++++++++++++++++++++++++++++++++ >> drivers/pci/pci.h | 8 +++++++- >> include/linux/pci.h | 4 ++++ >> 5 files changed, 62 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt >> index 742f69d..3f2a7c9 100644 >> --- a/Documentation/kernel-parameters.txt >> +++ b/Documentation/kernel-parameters.txt >> @@ -2857,6 +2857,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. >> PAGE_SIZE is used as alignment. >> PCI-PCI bridge can be specified, if resource >> windows need to be expanded. >> + resource_page_aligned= Enable/disable enforcing the alignment >> + of all PCI devices' memory resources to be >> + at least PAGE_SIZE if resources reallocation >> + is done by kernel. >> + Format: { "on" | "off" } >> ecrc= Enable/disable PCIe ECRC (transaction layer >> end-to-end CRC checking). >> bios: Use BIOS/firmware settings. This is the >> diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h >> index 3453bd8..2d2b3ef 100644 >> --- a/arch/powerpc/include/asm/pci.h >> +++ b/arch/powerpc/include/asm/pci.h >> @@ -136,6 +136,17 @@ extern pgprot_t pci_phys_mem_access_prot(struct file *file, >> unsigned long pfn, >> unsigned long size, >> pgprot_t prot); >> +#ifdef CONFIG_PPC64 >> + >> +/* For PPC64, We enforce all PCI MMIO BARs to be page aligned >> + * by default. This would be helpful to improve performance >> + * when we passthrough a PCI device of which BARs are smaller >> + * than PAGE_SIZE(64KB). And we can use kernel parameter >> + * "pci=resource_page_aligned=off" to disable it. >> + */ >> +#define HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED 1 >> + >> +#endif >> >> #define HAVE_ARCH_PCI_RESOURCE_TO_USER >> extern void pci_resource_to_user(const struct pci_dev *dev, int bar, >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >> index 314db8c..7b21238 100644 >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -99,6 +99,9 @@ u8 pci_cache_line_size; >> */ >> unsigned int pcibios_max_latency = 255; >> >> +bool pci_resources_page_aligned = >> + IS_ENABLED(HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED); > I don't think this is proper use of IS_ENABLED, which seems to be > targeted at CONFIG_ type options. You could define this as that in an > arch Kconfig. Is it better that we define this as a pci Kconfig and select it in arch Kconfig? >> + >> /* If set, the PCIe ARI capability will not be used. */ >> static bool pcie_ari_disabled; >> >> @@ -4746,6 +4749,35 @@ static ssize_t pci_resource_alignment_store(struct bus_type *bus, >> BUS_ATTR(resource_alignment, 0644, pci_resource_alignment_show, >> pci_resource_alignment_store); >> >> +static void pci_resources_get_page_aligned(char *str) >> +{ >> + if (!strncmp(str, "off", 3)) >> + pci_resources_page_aligned = false; >> + else if (!strncmp(str, "on", 2)) >> + pci_resources_page_aligned = true; >> +} > "get"? How about pci_resources_parse_page_aligned_param()? >> + >> +/* >> + * This function checks whether PCI BARs' mmio page will be shared >> + * with other BARs. >> + */ >> +bool pci_resources_share_page(struct pci_dev *dev, int resno) >> +{ >> + struct resource *res = dev->resource + resno; >> + >> + if (resource_size(res) >= PAGE_SIZE) >> + return false; >> + if (pci_resources_page_aligned && !(res->start & ~PAGE_MASK) && >> + res->flags & IORESOURCE_MEM) { >> + if (res->sibling) >> + return (res->sibling->start & ~PAGE_MASK); >> + else >> + return false; >> + } >> + return true; >> +} >> +EXPORT_SYMBOL_GPL(pci_resources_share_page); >> + >> static int __init pci_resource_alignment_sysfs_init(void) >> { >> return bus_create_file(&pci_bus_type, >> @@ -4859,6 +4891,9 @@ static int __init pci_setup(char *str) >> } else if (!strncmp(str, "resource_alignment=", 19)) { >> pci_set_resource_alignment_param(str + 19, >> strlen(str + 19)); >> + } else if (!strncmp(str, "resource_page_aligned=", >> + 22)) { >> + pci_resources_get_page_aligned(str + 22); > Doesn't this seem rather redundant with the option right above it, > resource_alignment=? Why not modify that to support syntax where all > devices get the same alignment? > The kernel option will be used to do two things. Firstly, the option can be used to enable all devices to be page aligned. Secondly, we can use the option to disable it when the Kconfig option mentioned above enable all devices to be page aligned by default. We can easily modify this option "resource_alignment=" to do the first thing. But I didn't find a proper way to modify it to do the second thing. >> } else if (!strncmp(str, "ecrc=", 5)) { >> pcie_ecrc_get_policy(str + 5); >> } else if (!strncmp(str, "hpiosize=", 9)) { >> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h >> index d390fc1..b9b333d 100644 >> --- a/drivers/pci/pci.h >> +++ b/drivers/pci/pci.h >> @@ -312,11 +312,17 @@ static inline resource_size_t pci_resource_alignment(struct pci_dev *dev, >> #ifdef CONFIG_PCI_IOV >> int resno = res - dev->resource; >> >> - if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) >> + if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) { >> + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) >> + return PAGE_ALIGN(pci_sriov_resource_alignment(dev, >> + resno)); >> return pci_sriov_resource_alignment(dev, resno); >> + } >> #endif >> if (dev->class >> 8 == PCI_CLASS_BRIDGE_CARDBUS) >> return pci_cardbus_resource_alignment(res); >> + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) >> + return PAGE_ALIGN(resource_alignment(res)); >> return resource_alignment(res); >> } > > Since we already have resource_alignment=, shouldn't we already have the > code in place to re-align? Yes, this code can do the re-aligning. But we can't reuse the code because it re-align device's bars by changing their sizes, which can potentially break some drivers. I'm thinking if we can use IORESOURCE_STARTALIGN for this. Thanks. Regards, Yongji Xie -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 2016-01-29 at 18:37 +0800, Yongji Xie wrote: > On 2016/1/29 6:46, Alex Williamson wrote: > > On Fri, 2016-01-15 at 15:06 +0800, Yongji Xie wrote: > > > When vfio passthrough a PCI device of which MMIO BARs > > > are smaller than PAGE_SIZE, guest will not handle the > > > mmio accesses to the BARs which leads to mmio emulations > > > in host. > > > > > > This is because vfio will not allow to passthrough one > > > BAR's mmio page which may be shared with other BARs. > > > > > > To solve this performance issue, this patch adds a kernel > > > parameter "pci=resource_page_aligned=on" to enforce > > > the alignment of all MMIO BARs to be at least PAGE_SIZE, > > > so that one BAR's mmio page would not be shared with other > > > BARs. We can also disable it through kernel parameter > > > "pci=resource_page_aligned=off". > > > > > > For the default value of the parameter, we think it should be > > > arch-independent, so we add a macro > > > HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED to change it. And we > > > define this macro to enable this parameter by default on PPC64 > > > platform which can easily hit this performance issue because > > > its PAGE_SIZE is 64KB. > > > > > > Note that the kernel parameter won't works if kernel doesn't do > > > resources reallocation. > > And where do you account for this so that we know whether it's really in > > effect? > > We can check the flag PCI_PROBE_ONLY to know whether kernel do > resources reallocation. Then we know if the kernel parameter is really > in effect. > > enum { > /* Force re-assigning all resources (ignore firmware > * setup completely) > */ > PCI_REASSIGN_ALL_RSRC = 0x00000001, > > /* Re-assign all bus numbers */ > PCI_REASSIGN_ALL_BUS = 0x00000002, > > /* Do not try to assign, just use existing setup */ > ---> PCI_PROBE_ONLY = 0x00000004, > > And I will add this to commit log. We need more than a commit log entry for this, what's the purpose of the pci_resources_share_page() function if we don't know if this is in effect? > > > Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com> > > > --- > > > Documentation/kernel-parameters.txt | 5 +++++ > > > arch/powerpc/include/asm/pci.h | 11 +++++++++++ > > > drivers/pci/pci.c | 35 +++++++++++++++++++++++++++++++++++ > > > drivers/pci/pci.h | 8 +++++++- > > > include/linux/pci.h | 4 ++++ > > > 5 files changed, 62 insertions(+), 1 deletion(-) > > > > > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > > > index 742f69d..3f2a7c9 100644 > > > --- a/Documentation/kernel-parameters.txt > > > +++ b/Documentation/kernel-parameters.txt > > > @@ -2857,6 +2857,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > > > PAGE_SIZE is used as alignment. > > > PCI-PCI bridge can be specified, if resource > > > windows need to be expanded. > > > + resource_page_aligned= Enable/disable enforcing the alignment > > > + of all PCI devices' memory resources to be > > > + at least PAGE_SIZE if resources reallocation > > > + is done by kernel. > > > + Format: { "on" | "off" } > > > ecrc= Enable/disable PCIe ECRC (transaction layer > > > end-to-end CRC checking). > > > bios: Use BIOS/firmware settings. This is the > > > diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h > > > index 3453bd8..2d2b3ef 100644 > > > --- a/arch/powerpc/include/asm/pci.h > > > +++ b/arch/powerpc/include/asm/pci.h > > > @@ -136,6 +136,17 @@ extern pgprot_t pci_phys_mem_access_prot(struct file *file, > > > unsigned long pfn, > > > unsigned long size, > > > pgprot_t prot); > > > +#ifdef CONFIG_PPC64 > > > + > > > +/* For PPC64, We enforce all PCI MMIO BARs to be page aligned > > > + * by default. This would be helpful to improve performance > > > + * when we passthrough a PCI device of which BARs are smaller > > > + * than PAGE_SIZE(64KB). And we can use kernel parameter > > > + * "pci=resource_page_aligned=off" to disable it. > > > + */ > > > +#define HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED 1 > > > + > > > +#endif > > > > > > #define HAVE_ARCH_PCI_RESOURCE_TO_USER > > > extern void pci_resource_to_user(const struct pci_dev *dev, int bar, > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > > > index 314db8c..7b21238 100644 > > > --- a/drivers/pci/pci.c > > > +++ b/drivers/pci/pci.c > > > @@ -99,6 +99,9 @@ u8 pci_cache_line_size; > > > */ > > > unsigned int pcibios_max_latency = 255; > > > > > > +bool pci_resources_page_aligned = > > > + IS_ENABLED(HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED); > > I don't think this is proper use of IS_ENABLED, which seems to be > > targeted at CONFIG_ type options. You could define this as that in an > > arch Kconfig. > > Is it better that we define this as a pci Kconfig and select it in arch > Kconfig? If you want to use IS_ENABLE here, I would think so. > > > + > > > /* If set, the PCIe ARI capability will not be used. */ > > > static bool pcie_ari_disabled; > > > > > > @@ -4746,6 +4749,35 @@ static ssize_t pci_resource_alignment_store(struct bus_type *bus, > > > BUS_ATTR(resource_alignment, 0644, pci_resource_alignment_show, > > > pci_resource_alignment_store); > > > > > > +static void pci_resources_get_page_aligned(char *str) > > > +{ > > > + if (!strncmp(str, "off", 3)) > > > + pci_resources_page_aligned = false; > > > + else if (!strncmp(str, "on", 2)) > > > + pci_resources_page_aligned = true; > > > +} > > "get"? > > How about pci_resources_parse_page_aligned_param()? Better. > > > + > > > +/* > > > + * This function checks whether PCI BARs' mmio page will be shared > > > + * with other BARs. > > > + */ > > > +bool pci_resources_share_page(struct pci_dev *dev, int resno) > > > +{ > > > + struct resource *res = dev->resource + resno; > > > + > > > + if (resource_size(res) >= PAGE_SIZE) > > > + return false; > > > + if (pci_resources_page_aligned && !(res->start & ~PAGE_MASK) && > > > + res->flags & IORESOURCE_MEM) { > > > + if (res->sibling) > > > + return (res->sibling->start & ~PAGE_MASK); > > > + else > > > + return false; > > > + } > > > + return true; > > > +} > > > +EXPORT_SYMBOL_GPL(pci_resources_share_page); > > > + > > > static int __init pci_resource_alignment_sysfs_init(void) > > > { > > > return bus_create_file(&pci_bus_type, > > > @@ -4859,6 +4891,9 @@ static int __init pci_setup(char *str) > > > } else if (!strncmp(str, "resource_alignment=", 19)) { > > > pci_set_resource_alignment_param(str + 19, > > > strlen(str + 19)); > > > + } else if (!strncmp(str, "resource_page_aligned=", > > > + 22)) { > > > + pci_resources_get_page_aligned(str + 22); > > Doesn't this seem rather redundant with the option right above it, > > resource_alignment=? Why not modify that to support syntax where all > > devices get the same alignment? > > > > The kernel option will be used to do two things. > > Firstly, the option can be used to enable all devices to be page aligned. > > Secondly, we can use the option to disable it when the Kconfig option > mentioned above enable all devices to be page aligned by default. > > We can easily modify this option "resource_alignment=" to do the first > thing. But I didn't find a proper way to modify it to do the second thing. You could allow an arch specified default which is overridden by specifying a resource_alignment= value. Then you need a way to disable it, which you could simply do by making pci_set_resource_alignment_param() able to parse something like resource_alignment=off. > > > } else if (!strncmp(str, "ecrc=", 5)) { > > > pcie_ecrc_get_policy(str + 5); > > > } else if (!strncmp(str, "hpiosize=", 9)) { > > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > > > index d390fc1..b9b333d 100644 > > > --- a/drivers/pci/pci.h > > > +++ b/drivers/pci/pci.h > > > @@ -312,11 +312,17 @@ static inline resource_size_t pci_resource_alignment(struct pci_dev *dev, > > > #ifdef CONFIG_PCI_IOV > > > int resno = res - dev->resource; > > > > > > - if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) > > > + if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) { > > > + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) > > > + return PAGE_ALIGN(pci_sriov_resource_alignment(dev, > > > + resno)); > > > return pci_sriov_resource_alignment(dev, resno); > > > + } > > > #endif > > > if (dev->class >> 8 == PCI_CLASS_BRIDGE_CARDBUS) > > > return pci_cardbus_resource_alignment(res); > > > + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) > > > + return PAGE_ALIGN(resource_alignment(res)); > > > return resource_alignment(res); > > > } > > > > Since we already have resource_alignment=, shouldn't we already have the > > code in place to re-align? > > Yes, this code can do the re-aligning. But we can't reuse the code because > it re-align device's bars by changing their sizes, which can potentially > break > some drivers. > > I'm thinking if we can use IORESOURCE_STARTALIGN for this. Thanks. Shouldn't we fix resource_alignment= then to make it behave in a more compatible way then? resource_alignment=64k,resource_resize=off? Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2016/1/30 3:01, Alex Williamson wrote: > On Fri, 2016-01-29 at 18:37 +0800, Yongji Xie wrote: >> On 2016/1/29 6:46, Alex Williamson wrote: >>> On Fri, 2016-01-15 at 15:06 +0800, Yongji Xie wrote: >>>> When vfio passthrough a PCI device of which MMIO BARs >>>> are smaller than PAGE_SIZE, guest will not handle the >>>> mmio accesses to the BARs which leads to mmio emulations >>>> in host. >>>> >>>> This is because vfio will not allow to passthrough one >>>> BAR's mmio page which may be shared with other BARs. >>>> >>>> To solve this performance issue, this patch adds a kernel >>>> parameter "pci=resource_page_aligned=on" to enforce >>>> the alignment of all MMIO BARs to be at least PAGE_SIZE, >>>> so that one BAR's mmio page would not be shared with other >>>> BARs. We can also disable it through kernel parameter >>>> "pci=resource_page_aligned=off". >>>> >>>> For the default value of the parameter, we think it should be >>>> arch-independent, so we add a macro >>>> HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED to change it. And we >>>> define this macro to enable this parameter by default on PPC64 >>>> platform which can easily hit this performance issue because >>>> its PAGE_SIZE is 64KB. >>>> >>>> Note that the kernel parameter won't works if kernel doesn't do >>>> resources reallocation. >>> And where do you account for this so that we know whether it's really in >>> effect? >> >> We can check the flag PCI_PROBE_ONLY to know whether kernel do >> resources reallocation. Then we know if the kernel parameter is really >> in effect. >> >> enum { >> /* Force re-assigning all resources (ignore firmware >> * setup completely) >> */ >> PCI_REASSIGN_ALL_RSRC = 0x00000001, >> >> /* Re-assign all bus numbers */ >> PCI_REASSIGN_ALL_BUS = 0x00000002, >> >> /* Do not try to assign, just use existing setup */ >> ---> PCI_PROBE_ONLY = 0x00000004, >> >> And I will add this to commit log. > We need more than a commit log entry for this, what's the purpose of the > pci_resources_share_page() function if we don't know if this is in > effect? It seems the parameter will be always in effect if we reuse the re-aligning code of parameter "resource_alignment=" in pci_reassigndev_resource_alignment(). >>>> Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com> >>>> --- >>>> Documentation/kernel-parameters.txt | 5 +++++ >>>> arch/powerpc/include/asm/pci.h | 11 +++++++++++ >>>> drivers/pci/pci.c | 35 +++++++++++++++++++++++++++++++++++ >>>> drivers/pci/pci.h | 8 +++++++- >>>> include/linux/pci.h | 4 ++++ >>>> 5 files changed, 62 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt >>>> index 742f69d..3f2a7c9 100644 >>>> --- a/Documentation/kernel-parameters.txt >>>> +++ b/Documentation/kernel-parameters.txt >>>> @@ -2857,6 +2857,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. >>>> PAGE_SIZE is used as alignment. >>>> PCI-PCI bridge can be specified, if resource >>>> windows need to be expanded. >>>> + resource_page_aligned= Enable/disable enforcing the alignment >>>> + of all PCI devices' memory resources to be >>>> + at least PAGE_SIZE if resources reallocation >>>> + is done by kernel. >>>> + Format: { "on" | "off" } >>>> ecrc= Enable/disable PCIe ECRC (transaction layer >>>> end-to-end CRC checking). >>>> bios: Use BIOS/firmware settings. This is the >>>> diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h >>>> index 3453bd8..2d2b3ef 100644 >>>> --- a/arch/powerpc/include/asm/pci.h >>>> +++ b/arch/powerpc/include/asm/pci.h >>>> @@ -136,6 +136,17 @@ extern pgprot_t pci_phys_mem_access_prot(struct file *file, >>>> unsigned long pfn, >>>> unsigned long size, >>>> pgprot_t prot); >>>> +#ifdef CONFIG_PPC64 >>>> + >>>> +/* For PPC64, We enforce all PCI MMIO BARs to be page aligned >>>> + * by default. This would be helpful to improve performance >>>> + * when we passthrough a PCI device of which BARs are smaller >>>> + * than PAGE_SIZE(64KB). And we can use kernel parameter >>>> + * "pci=resource_page_aligned=off" to disable it. >>>> + */ >>>> +#define HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED 1 >>>> + >>>> +#endif >>>> >>>> #define HAVE_ARCH_PCI_RESOURCE_TO_USER >>>> extern void pci_resource_to_user(const struct pci_dev *dev, int bar, >>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >>>> index 314db8c..7b21238 100644 >>>> --- a/drivers/pci/pci.c >>>> +++ b/drivers/pci/pci.c >>>> @@ -99,6 +99,9 @@ u8 pci_cache_line_size; >>>> */ >>>> unsigned int pcibios_max_latency = 255; >>>> >>>> +bool pci_resources_page_aligned = >>>> + IS_ENABLED(HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED); >>> I don't think this is proper use of IS_ENABLED, which seems to be >>> targeted at CONFIG_ type options. You could define this as that in an >>> arch Kconfig. >> >> Is it better that we define this as a pci Kconfig and select it in arch >> Kconfig? > If you want to use IS_ENABLE here, I would think so. Actually, I'm not sure if it's necessary to add a Kconfig option for it. I prefer to do it like previous version: #ifdef HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED bool pci_resources_page_aligned = true; #else bool pci_resources_page_aligned; #endif >>>> + >>>> /* If set, the PCIe ARI capability will not be used. */ >>>> static bool pcie_ari_disabled; >>>> >>>> @@ -4746,6 +4749,35 @@ static ssize_t pci_resource_alignment_store(struct bus_type *bus, >>>> BUS_ATTR(resource_alignment, 0644, pci_resource_alignment_show, >>>> pci_resource_alignment_store); >>>> >>>> +static void pci_resources_get_page_aligned(char *str) >>>> +{ >>>> + if (!strncmp(str, "off", 3)) >>>> + pci_resources_page_aligned = false; >>>> + else if (!strncmp(str, "on", 2)) >>>> + pci_resources_page_aligned = true; >>>> +} >>> "get"? >> >> How about pci_resources_parse_page_aligned_param()? > Better. > >>>> + >>>> +/* >>>> + * This function checks whether PCI BARs' mmio page will be shared >>>> + * with other BARs. >>>> + */ >>>> +bool pci_resources_share_page(struct pci_dev *dev, int resno) >>>> +{ >>>> + struct resource *res = dev->resource + resno; >>>> + >>>> + if (resource_size(res) >= PAGE_SIZE) >>>> + return false; >>>> + if (pci_resources_page_aligned && !(res->start & ~PAGE_MASK) && >>>> + res->flags & IORESOURCE_MEM) { >>>> + if (res->sibling) >>>> + return (res->sibling->start & ~PAGE_MASK); >>>> + else >>>> + return false; >>>> + } >>>> + return true; >>>> +} >>>> +EXPORT_SYMBOL_GPL(pci_resources_share_page); >>>> + >>>> static int __init pci_resource_alignment_sysfs_init(void) >>>> { >>>> return bus_create_file(&pci_bus_type, >>>> @@ -4859,6 +4891,9 @@ static int __init pci_setup(char *str) >>>> } else if (!strncmp(str, "resource_alignment=", 19)) { >>>> pci_set_resource_alignment_param(str + 19, >>>> strlen(str + 19)); >>>> + } else if (!strncmp(str, "resource_page_aligned=", >>>> + 22)) { >>>> + pci_resources_get_page_aligned(str + 22); >>> Doesn't this seem rather redundant with the option right above it, >>> resource_alignment=? Why not modify that to support syntax where all >>> devices get the same alignment? >>> >> >> The kernel option will be used to do two things. >> >> Firstly, the option can be used to enable all devices to be page aligned. >> >> Secondly, we can use the option to disable it when the Kconfig option >> mentioned above enable all devices to be page aligned by default. >> >> We can easily modify this option "resource_alignment=" to do the first >> thing. But I didn't find a proper way to modify it to do the second thing. > You could allow an arch specified default which is overridden by > specifying a resource_alignment= value. Then you need a way to disable > it, which you could simply do by making > pci_set_resource_alignment_param() able to parse something like > resource_alignment=off. We just want to enforce the alignment of all MMIO BARs to be page aligned in this patch. And both the arch specified default value and pci_resources_page_aligned are something like *on/off* enforcing the alignment of resources to be page aligned. So I think it's better to add a parameter whose format is *on/off*. If we reuse "resource_alignment=", we need an additional translation from "resource_alignment="(format: [<order of align>@]...) to pci_resources_page_aligned(format: true/false). And "resource_alignment=" is always used to specify alignments of devices. Would it be misunderstanding to add some syntax like "resource_alignment=off"? >>>> } else if (!strncmp(str, "ecrc=", 5)) { >>>> pcie_ecrc_get_policy(str + 5); >>>> } else if (!strncmp(str, "hpiosize=", 9)) { >>>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h >>>> index d390fc1..b9b333d 100644 >>>> --- a/drivers/pci/pci.h >>>> +++ b/drivers/pci/pci.h >>>> @@ -312,11 +312,17 @@ static inline resource_size_t pci_resource_alignment(struct pci_dev *dev, >>>> #ifdef CONFIG_PCI_IOV >>>> int resno = res - dev->resource; >>>> >>>> - if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) >>>> + if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) { >>>> + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) >>>> + return PAGE_ALIGN(pci_sriov_resource_alignment(dev, >>>> + resno)); >>>> return pci_sriov_resource_alignment(dev, resno); >>>> + } >>>> #endif >>>> if (dev->class >> 8 == PCI_CLASS_BRIDGE_CARDBUS) >>>> return pci_cardbus_resource_alignment(res); >>>> + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) >>>> + return PAGE_ALIGN(resource_alignment(res)); >>>> return resource_alignment(res); >>>> } >>> >>> Since we already have resource_alignment=, shouldn't we already have the >>> code in place to re-align? >> >> Yes, this code can do the re-aligning. But we can't reuse the code because >> it re-align device's bars by changing their sizes, which can potentially >> break >> some drivers. >> >> I'm thinking if we can use IORESOURCE_STARTALIGN for this. Thanks. > Shouldn't we fix resource_alignment= then to make it behave in a more > compatible way then? resource_alignment=64k,resource_resize=off? > Thanks, > > Alex > Good point! We can add something like "resource_resize=off" to "resource_alignment=". Then we can reuse the re-aligning code. Thanks. Regards, Yongji Xie -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 742f69d..3f2a7c9 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2857,6 +2857,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. PAGE_SIZE is used as alignment. PCI-PCI bridge can be specified, if resource windows need to be expanded. + resource_page_aligned= Enable/disable enforcing the alignment + of all PCI devices' memory resources to be + at least PAGE_SIZE if resources reallocation + is done by kernel. + Format: { "on" | "off" } ecrc= Enable/disable PCIe ECRC (transaction layer end-to-end CRC checking). bios: Use BIOS/firmware settings. This is the diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h index 3453bd8..2d2b3ef 100644 --- a/arch/powerpc/include/asm/pci.h +++ b/arch/powerpc/include/asm/pci.h @@ -136,6 +136,17 @@ extern pgprot_t pci_phys_mem_access_prot(struct file *file, unsigned long pfn, unsigned long size, pgprot_t prot); +#ifdef CONFIG_PPC64 + +/* For PPC64, We enforce all PCI MMIO BARs to be page aligned + * by default. This would be helpful to improve performance + * when we passthrough a PCI device of which BARs are smaller + * than PAGE_SIZE(64KB). And we can use kernel parameter + * "pci=resource_page_aligned=off" to disable it. + */ +#define HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED 1 + +#endif #define HAVE_ARCH_PCI_RESOURCE_TO_USER extern void pci_resource_to_user(const struct pci_dev *dev, int bar, diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 314db8c..7b21238 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -99,6 +99,9 @@ u8 pci_cache_line_size; */ unsigned int pcibios_max_latency = 255; +bool pci_resources_page_aligned = + IS_ENABLED(HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED); + /* If set, the PCIe ARI capability will not be used. */ static bool pcie_ari_disabled; @@ -4746,6 +4749,35 @@ static ssize_t pci_resource_alignment_store(struct bus_type *bus, BUS_ATTR(resource_alignment, 0644, pci_resource_alignment_show, pci_resource_alignment_store); +static void pci_resources_get_page_aligned(char *str) +{ + if (!strncmp(str, "off", 3)) + pci_resources_page_aligned = false; + else if (!strncmp(str, "on", 2)) + pci_resources_page_aligned = true; +} + +/* + * This function checks whether PCI BARs' mmio page will be shared + * with other BARs. + */ +bool pci_resources_share_page(struct pci_dev *dev, int resno) +{ + struct resource *res = dev->resource + resno; + + if (resource_size(res) >= PAGE_SIZE) + return false; + if (pci_resources_page_aligned && !(res->start & ~PAGE_MASK) && + res->flags & IORESOURCE_MEM) { + if (res->sibling) + return (res->sibling->start & ~PAGE_MASK); + else + return false; + } + return true; +} +EXPORT_SYMBOL_GPL(pci_resources_share_page); + static int __init pci_resource_alignment_sysfs_init(void) { return bus_create_file(&pci_bus_type, @@ -4859,6 +4891,9 @@ static int __init pci_setup(char *str) } else if (!strncmp(str, "resource_alignment=", 19)) { pci_set_resource_alignment_param(str + 19, strlen(str + 19)); + } else if (!strncmp(str, "resource_page_aligned=", + 22)) { + pci_resources_get_page_aligned(str + 22); } else if (!strncmp(str, "ecrc=", 5)) { pcie_ecrc_get_policy(str + 5); } else if (!strncmp(str, "hpiosize=", 9)) { diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index d390fc1..b9b333d 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -312,11 +312,17 @@ static inline resource_size_t pci_resource_alignment(struct pci_dev *dev, #ifdef CONFIG_PCI_IOV int resno = res - dev->resource; - if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) + if (resno >= PCI_IOV_RESOURCES && resno <= PCI_IOV_RESOURCE_END) { + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) + return PAGE_ALIGN(pci_sriov_resource_alignment(dev, + resno)); return pci_sriov_resource_alignment(dev, resno); + } #endif if (dev->class >> 8 == PCI_CLASS_BRIDGE_CARDBUS) return pci_cardbus_resource_alignment(res); + if (pci_resources_page_aligned && res->flags & IORESOURCE_MEM) + return PAGE_ALIGN(resource_alignment(res)); return resource_alignment(res); } diff --git a/include/linux/pci.h b/include/linux/pci.h index 6ae25aa..b640d65 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -1530,6 +1530,10 @@ static inline int pci_get_new_domain_nr(void) { return -ENOSYS; } (pci_resource_end((dev), (bar)) - \ pci_resource_start((dev), (bar)) + 1)) +extern bool pci_resources_page_aligned; + +bool pci_resources_share_page(struct pci_dev *dev, int resno); + /* Similar to the helpers above, these manipulate per-pci_dev * driver-specific data. They are really just a wrapper around * the generic device structure functions of these calls.
When vfio passthrough a PCI device of which MMIO BARs are smaller than PAGE_SIZE, guest will not handle the mmio accesses to the BARs which leads to mmio emulations in host. This is because vfio will not allow to passthrough one BAR's mmio page which may be shared with other BARs. To solve this performance issue, this patch adds a kernel parameter "pci=resource_page_aligned=on" to enforce the alignment of all MMIO BARs to be at least PAGE_SIZE, so that one BAR's mmio page would not be shared with other BARs. We can also disable it through kernel parameter "pci=resource_page_aligned=off". For the default value of the parameter, we think it should be arch-independent, so we add a macro HAVE_PCI_DEFAULT_RESOURCES_PAGE_ALIGNED to change it. And we define this macro to enable this parameter by default on PPC64 platform which can easily hit this performance issue because its PAGE_SIZE is 64KB. Note that the kernel parameter won't works if kernel doesn't do resources reallocation. Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com> --- Documentation/kernel-parameters.txt | 5 +++++ arch/powerpc/include/asm/pci.h | 11 +++++++++++ drivers/pci/pci.c | 35 +++++++++++++++++++++++++++++++++++ drivers/pci/pci.h | 8 +++++++- include/linux/pci.h | 4 ++++ 5 files changed, 62 insertions(+), 1 deletion(-)