Hi, Bibo, On Fri, Jun 9, 2023 at 10:20 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote: > > Some PCI devices have only 4K memory space size, it is normal in general > machines and aligned with page size. However some architectures which > support different page size, default page size on LoongArch is 16K, and > ARM64 supports page size varying from 4K to 64K. On machines where larger > page size is use, memory space region of two different pci devices may be > in one page. It is not safe with mmu protection, also VFIO pci device > driver requires base address of pci memory space page aligned, so that it > can be memory mapped to qemu user space when it is passed-through to vm. > > It consumes more pci memory resource with page size alignment requirement, > here extra option PCI_MEMRES_PAGE_ALIGN is added, it can be enabled by > different architectures. > > Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx> > --- > Change history > v4: add extra kernel option PCI_MEMRES_PAGE_ALIGN to set memory resource > page aligned. > > v3: move alignment requirement to generic pci code > > v2: add pci resource alignment requirement in arch specified function > pcibios_align_resource on arm64/LoongArch platforms > > --- > arch/loongarch/Kconfig | 1 + > drivers/pci/Kconfig | 3 +++ > drivers/pci/setup-res.c | 7 +++++++ > 3 files changed, 11 insertions(+) > > diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig > index d38b066fc931..65b2f6ba9f8e 100644 > --- a/arch/loongarch/Kconfig > +++ b/arch/loongarch/Kconfig > @@ -142,6 +142,7 @@ config LOONGARCH > select PCI_LOONGSON > select PCI_MSI_ARCH_FALLBACKS > select PCI_QUIRKS > + select PCI_MEMRES_PAGE_ALIGN > select PERF_USE_VMALLOC > select RTC_LIB > select SMP > diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig > index 9309f2469b41..9be5f85ff9dc 100644 > --- a/drivers/pci/Kconfig > +++ b/drivers/pci/Kconfig > @@ -128,6 +128,9 @@ config PCI_LOCKLESS_CONFIG > config PCI_BRIDGE_EMUL > bool > > +config PCI_MEMRES_PAGE_ALIGN > + bool > + > config PCI_IOV > bool "PCI IOV support" > select PCI_ATS > diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c > index 967f9a758923..6ad76734a670 100644 > --- a/drivers/pci/setup-res.c > +++ b/drivers/pci/setup-res.c > @@ -339,6 +339,13 @@ int pci_assign_resource(struct pci_dev *dev, int resno) > return -EINVAL; > } > > +#ifdef CONFIG_PCI_MEMRES_PAGE_ALIGN > + /* > + * force minimum page alignment for vfio pci usage > + */ > + if (res->flags & IORESOURCE_MEM) > + align = max_t(resource_size_t, PAGE_SIZE, align); > +#endif Does this really have its effect? The common version of pcibios_align_resource() simply returns res->start, and doesn't care about the 'align' parameter. Huacai > size = resource_size(res); > ret = _pci_assign_resource(dev, resno, size, align); > > -- > 2.27.0 >
