Re: [RFC PATCH v4 5/7] vfio-pci: Allow to mmap sub-page MMIO BARs if the mmio page is exclusive

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On 2016/3/17 0:30, Alex Williamson wrote:
On Mon,  7 Mar 2016 15:48:36 +0800
Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx> 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 PCI
resource allocator can make sure these BARs' mmio page will
not be shared with other BARs.

Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
---
  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

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