On Thu, 2015-12-17 at 18:26 +0800, yongji xie wrote: > > On 2015/12/17 4:04, Alex Williamson wrote: > > On Fri, 2015-12-11 at 16:53 +0800, Yongji Xie wrote: > > > Current vfio-pci implementation disallows to mmap > > > sub-page(size < PAGE_SIZE) MMIO BARs because these BARs' mmio > > > page > > > may be shared with other BARs. > > > > > > But we should allow to mmap these sub-page MMIO BARs if all MMIO > > > BARs > > > are page aligned which leads the BARs' mmio page would not be > > > shared > > > with other BARs. > > > > > > This patch adds support for this case and we also add a > > > VFIO_DEVICE_FLAGS_PCI_PAGE_ALIGNED flag to notify userspace that > > > platform supports all MMIO BARs to be page aligned. > > > > > > Signed-off-by: Yongji Xie <xyj...@linux.vnet.ibm.com> > > > --- > > > drivers/vfio/pci/vfio_pci.c | 10 +++++++++- > > > drivers/vfio/pci/vfio_pci_private.h | 5 +++++ > > > include/uapi/linux/vfio.h | 2 ++ > > > 3 files changed, 16 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/vfio/pci/vfio_pci.c > > > b/drivers/vfio/pci/vfio_pci.c > > > index 32b88bd..dbcad99 100644 > > > --- a/drivers/vfio/pci/vfio_pci.c > > > +++ b/drivers/vfio/pci/vfio_pci.c > > > @@ -443,6 +443,9 @@ static long vfio_pci_ioctl(void *device_data, > > > if (vdev->reset_works) > > > info.flags |= VFIO_DEVICE_FLAGS_RESET; > > > > > > + if (vfio_pci_bar_page_aligned()) > > > + info.flags |= > > > VFIO_DEVICE_FLAGS_PCI_PAGE_ALIGNED; > > > + > > > info.num_regions = VFIO_PCI_NUM_REGIONS; > > > info.num_irqs = VFIO_PCI_NUM_IRQS; > > > > > > @@ -479,7 +482,8 @@ static long vfio_pci_ioctl(void *device_data, > > > VFIO_REGION_INFO_FLAG_WRIT > > > E; > > > if (IS_ENABLED(CONFIG_VFIO_PCI_MMAP) && > > > pci_resource_flags(pdev, > > > info.index) & > > > - IORESOURCE_MEM && info.size >= > > > PAGE_SIZE) > > > + IORESOURCE_MEM && (info.size >= > > > PAGE_SIZE || > > > + vfio_pci_bar_page_aligned())) > > > info.flags |= > > > VFIO_REGION_INFO_FLAG_MMAP; > > > break; > > > case VFIO_PCI_ROM_REGION_INDEX: > > > @@ -855,6 +859,10 @@ static int vfio_pci_mmap(void *device_data, > > > struct vm_area_struct *vma) > > > return -EINVAL; > > > > > > phys_len = pci_resource_len(pdev, index); > > > + > > > + if (vfio_pci_bar_page_aligned()) > > > + phys_len = PAGE_ALIGN(phys_len); > > > + > > > req_len = vma->vm_end - vma->vm_start; > > > pgoff = vma->vm_pgoff & > > > ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - > > > 1); > > > diff --git a/drivers/vfio/pci/vfio_pci_private.h > > > b/drivers/vfio/pci/vfio_pci_private.h > > > index 0e7394f..319352a 100644 > > > --- a/drivers/vfio/pci/vfio_pci_private.h > > > +++ b/drivers/vfio/pci/vfio_pci_private.h > > > @@ -69,6 +69,11 @@ struct vfio_pci_device { > > > #define is_irq_none(vdev) (!(is_intx(vdev) || is_msi(vdev) || > > > is_msix(vdev))) > > > #define irq_is(vdev, type) (vdev->irq_type == type) > > > > > > +static inline bool vfio_pci_bar_page_aligned(void) > > > +{ > > > + return IS_ENABLED(CONFIG_PPC64); > > > +} > > I really dislike this. This is a problem for any architecture that > > runs on larger pages, and even an annoyance on 4k hosts. Why are > > we > > only solving it for PPC64? > Yes, I know it's a problem for other architectures. But I'm not sure > if > other archs prefer > to enforce the alignment of all BARs to be at least PAGE_SIZE which > would result in > some waste of address space. > > So I just propose a prototype and add PPC64 support here. And other > archs could decide > to use it or not by themselves. > > Can't we do something similar in the core PCI code and detect it? > So you mean we can do it like this: > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index d390fc1..f46c04d 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -320,6 +320,11 @@ static inline resource_size_t > pci_resource_alignment(struct pci_dev *dev, > return resource_alignment(res); > } > > +static inline bool pci_bar_page_aligned(void) > +{ > + return IS_ENABLED(CONFIG_PPC64); > +} > + > void pci_enable_acs(struct pci_dev *dev); > > struct pci_dev_reset_methods { > > or add a config option to indicate that PCI MMIO BARs should be page > aligned?
Yes, I'm thinking of a boot commandline option, maybe one that PPC64 can default to enabled if it chooses to. The problem is not unique to PPC64 and the solution should not be unique either. I don't want to need to revisit this for ARM, which we know is going to be similarly afflicted. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html