[Qemu-devel] [PATCH] vfio/pci-quirks: Set non-zero GMS memory size for IGD

[Dmitry Fleytman]

There is a claim that GMS memory is unused however
Intel Windows 10 drivers starting from V.4534 (10/7/2016)
allocate extra ~4G memory when GMS size set to 0.

This patch fixes this issue by seting IGD GMS memory
size to minimum by changing default value of x-igd-gms
device parameter.

Signed-off-by: Dmitry Fleytman <address@hidden>
---
 hw/vfio/pci-quirks.c | 13 +++++++++----
 hw/vfio/pci.c        |  2 +-
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
index 349085e..197cb90 100644
--- a/hw/vfio/pci-quirks.c
+++ b/hw/vfio/pci-quirks.c
@@ -1527,10 +1527,15 @@ static void vfio_probe_igd_bar4_quirk(VFIOPCIDevice 
*vdev, int nr)
     }
 
     /*
-     * Assume we have no GMS memory, but allow it to be overrided by device
-     * option (experimental).  The spec doesn't actually allow zero GMS when
-     * when IVD (IGD VGA Disable) is clear, but the claim is that it's unused,
-     * so let's not waste VM memory for it.
+     * There is a claim that GMS memory is unused and we want to waste for it
+     * as less VM memory as possible, however Intel Windows 10 drivers starting
+     * from V.4534 (10/7/2016) allocate extra ~4G memory when GMS size set to 
0.
+     * The spec as well doesn't actually allow zero GMS when IVD
+     * (IGD VGA Disable) is clear.
+     *
+     * Therefore we set GMS memory size to minimal by default via device
+     * option x-igd-gms (experimental) and allow further tweaking of this
+     * parameter.
      */
     gmch &= ~((gen < 8 ? 0x1f : 0xff) << (gen < 8 ? 3 : 8));
 
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index d4051cb..bda07b7 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -2982,7 +2982,7 @@ static Property vfio_pci_dev_properties[] = {
                        sub_vendor_id, PCI_ANY_ID),
     DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
                        sub_device_id, PCI_ANY_ID),
-    DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 0),
+    DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 1),
     /*
      * TODO - support passed fds... is this necessary?
      * DEFINE_PROP_STRING("vfiofd", VFIOPCIDevice, vfiofd_name),
-- 
2.9.4