On 2016/3/17 0:30, Alex Williamson wrote:

On Mon,  7 Mar 2016 15:48:36 +0800
Yongji Xie [off-list ref] wrote:

quoted

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 PCI
resource allocator can make sure these BARs' mmio page will
not be shared with other BARs.

Signed-off-by: Yongji Xie <redacted>
---
  drivers/vfio/pci/vfio_pci.c |    7 ++++++-
  1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 1ce1d36..49d7a69 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c

@@ -589,7 +589,8 @@ static long vfio_pci_ioctl(void *device_data,
  				     VFIO_REGION_INFO_FLAG_WRITE;
  			if (IS_ENABLED(CONFIG_VFIO_PCI_MMAP) &&
  			    pci_resource_flags(pdev, info.index) &
-			    IORESOURCE_MEM && info.size >= PAGE_SIZE) {
+			    IORESOURCE_MEM && !pci_resources_share_page(pdev,
+			    info.index)) {

this would be a preferable line wrap:

                             IORESOURCE_MEM &&
                             !pci_resources_share_page(pdev, info.index)) {

OK. I'll fix it.

Thanks,
Yongji Xie