[Qemu-devel] [RFC PATCH 3/3] vfio/pci: Add support for mmapping MSI-X table

[Yongji Xie <xyjxie@linux.vnet.ibm.com>]

The VFIO-PCI ioctl VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP flag indicate that
platform support mmapping MSI-X table.

With this flag set, we skip some MSI-X table check so that QEMU can
mmap MSI-X table successfully. And we also raise the priority of mmap
memory region in case of overlap with MSI-X/PBA memory region which
is added in msix_init().

Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
---
 hw/vfio/pci.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index a7c6171..bec301c 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1339,7 +1339,8 @@ static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled)
         }
 
         memory_region_set_enabled(&bar->region.mmap_mem, enabled);
-        if (vdev->msix && vdev->msix->table_bar == i) {
+        if (vdev->msix && vdev->msix->table_bar == i &&
+            !(vdev->vbasedev.flags & VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP)) {
             memory_region_set_enabled(&vdev->msix->mmap_mem, enabled);
         }
     }
@@ -1357,7 +1358,8 @@ static void vfio_unregister_bar(VFIOPCIDevice *vdev, int nr)
 
     memory_region_del_subregion(&bar->region.mem, &bar->region.mmap_mem);
 
-    if (vdev->msix && vdev->msix->table_bar == nr) {
+    if (vdev->msix && vdev->msix->table_bar == nr &&
+        !(vdev->vbasedev.flags & VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP)) {
         memory_region_del_subregion(&bar->region.mem, &vdev->msix->mmap_mem);
     }
 }
@@ -1374,7 +1376,8 @@ static void vfio_unmap_bar(VFIOPCIDevice *vdev, int nr)
 
     munmap(bar->region.mmap, memory_region_size(&bar->region.mmap_mem));
 
-    if (vdev->msix && vdev->msix->table_bar == nr) {
+    if (vdev->msix && vdev->msix->table_bar == nr &&
+        !(vdev->vbasedev.flags & VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP)) {
         munmap(vdev->msix->mmap, memory_region_size(&vdev->msix->mmap_mem));
     }
 }
@@ -1420,7 +1423,8 @@ static void vfio_map_bar(VFIOPCIDevice *vdev, int nr)
      * We can't mmap areas overlapping the MSIX vector table, so we
      * potentially insert a direct-mapped subregion before and after it.
      */
-    if (vdev->msix && vdev->msix->table_bar == nr) {
+    if (vdev->msix && vdev->msix->table_bar == nr &&
+        !(vdev->vbasedev.flags & VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP)) {
         size = vdev->msix->table_offset & qemu_real_host_page_mask;
     }
 
@@ -1429,9 +1433,14 @@ static void vfio_map_bar(VFIOPCIDevice *vdev, int nr)
                       &bar->region.mmap_mem, &bar->region.mmap,
                       size, 0, name)) {
         error_report("%s unsupported. Performance may be slow", name);
+    } else if (vdev->vbasedev.flags & VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP) {
+        memory_region_del_subregion(&bar->region.mem, &bar->region.mmap_mem);
+        memory_region_add_subregion_overlap(&bar->region.mem, 0,
+                      &bar->region.mmap_mem, 1);
     }
 
-    if (vdev->msix && vdev->msix->table_bar == nr) {
+    if (vdev->msix && vdev->msix->table_bar == nr &&
+        !(vdev->vbasedev.flags & VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP)) {
         uint64_t start;
 
         start = REAL_HOST_PAGE_ALIGN((uint64_t)vdev->msix->table_offset +
-- 
1.7.9.5