[+cc linux-pci, beginning of thread: https://lore.kernel.org/all/20230602030732.1047696-1-maobibo@xxxxxxxxxxx/] On Fri, Jun 02, 2023 at 12:11:02PM +0800, Huacai Chen wrote: > On Fri, Jun 2, 2023 at 11:07 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote: > > > > LoongArch linux kernel uses 16K page size by default, some pci devices have > > only 4K memory size, it is normal in general architectures. However memory > > space of different pci devices will share one physical page address space. > > This is not safe for mmu protection, also UIO and VFIO requires base > > address of pci memory space page aligned. > > > > This patch adds check with function pcibios_align_resource, and set base > > address of resource page aligned. > > > > Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx> > > --- > > arch/loongarch/pci/pci.c | 23 +++++++++++++++++++++++ > > 1 file changed, 23 insertions(+) > > > > diff --git a/arch/loongarch/pci/pci.c b/arch/loongarch/pci/pci.c > > index 2726639150bc..1380f3672ba2 100644 > > --- a/arch/loongarch/pci/pci.c > > +++ b/arch/loongarch/pci/pci.c > > @@ -83,6 +83,29 @@ int pcibios_alloc_irq(struct pci_dev *dev) > > return acpi_pci_irq_enable(dev); > > } > > > > +/* > > + * memory space size of some pci cards is 4K, it is separated with > > + * different pages for generic architectures, so that mmu protection can > > + * work with different pci cards. However page size for LoongArch system > > + * is 16K, memory space of different pci cards may share the same page > > + * on LoongArch, it is not safe here. > > + * Also uio drivers and vfio drivers sugguests that base address of memory > > + * space should page aligned. This function aligns base address with page size > > + */ > > +resource_size_t pcibios_align_resource(void *data, const struct resource *res, > > + resource_size_t size, resource_size_t align) > > +{ > > + resource_size_t start = res->start; > > + > > + if (res->flags & IORESOURCE_MEM) { > > + if (align & (PAGE_SIZE - 1)) { > > + align = PAGE_SIZE; > > + start = ALIGN(start, align); > I don't know whether this patch is really needed, but the logic here > has some problems. > > For example, if PAGE_SIZE=16KB, align=18KB, what should we do? Align > to 16KB or align to 32KB? IMO it should align to 32KB, but in your > patch it will align to 16KB. > > Huacai > > + } > > + } > > + return start; > > +} > > + > > static void pci_fixup_vgadev(struct pci_dev *pdev) > > { > > struct pci_dev *devp = NULL; > > -- > > 2.27.0 > >
