[Qemu-devel] [PULL 1/1] Revert "vfio/pci-quirks.c: Disable stolen memory for igd VFIO"

[Alex Williamson]

From: Xiong Zhang <address@hidden>

This reverts commit c2b2e158cc7b1cb431bd6039824ec13c3184a775.

The original patch intend to prevent linux i915 driver from using
stolen meory. But this patch breaks windows IGD driver loading on
Gen9+, as IGD HW will use stolen memory on Gen9+, once windows IGD
driver see zero size stolen memory, it will unload.
Meanwhile stolen memory will be disabled in 915 when i915 run as
a guest.

Signed-off-by: Xiong Zhang <address@hidden>
[aw: Gen9+ is SkyLake and newer]
Signed-off-by: Alex Williamson <address@hidden>
---
 hw/vfio/pci-quirks.c |   65 +++++++++++++++++++++-----------------------------
 1 file changed, 27 insertions(+), 38 deletions(-)

diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c
index e995e32deedf..e9b493b939db 100644
--- a/hw/vfio/pci-quirks.c
+++ b/hw/vfio/pci-quirks.c
@@ -1367,45 +1367,14 @@ static void vfio_probe_igd_bar4_quirk(VFIOPCIDevice 
*vdev, int nr)
     uint16_t cmd_orig, cmd;
     Error *err = NULL;
 
-    /* This must be an Intel VGA device. */
-    if (!vfio_pci_is(vdev, PCI_VENDOR_ID_INTEL, PCI_ANY_ID) ||
-        !vfio_is_vga(vdev) || nr != 4) {
-        return;
-    }
-
-    /*
-     * IGD is not a standard, they like to change their specs often.  We
-     * only attempt to support back to SandBridge and we hope that newer
-     * devices maintain compatibility with generation 8.
-     */
-    gen = igd_gen(vdev);
-    if (gen != 6 && gen != 8) {
-        error_report("IGD device %s is unsupported by IGD quirks, "
-                     "try SandyBridge or newer", vdev->vbasedev.name);
-        return;
-    }
-
-    /*
-     * Regardless of running in UPT or legacy mode, the guest graphics
-     * driver may attempt to use stolen memory, however only legacy mode
-     * has BIOS support for reserving stolen memory in the guest VM.
-     * Emulate the GMCH register in all cases and zero out the stolen
-     * memory size here. Legacy mode may request allocation and re-write
-     * this below.
-     */
-    gmch = vfio_pci_read_config(&vdev->pdev, IGD_GMCH, 4);
-    gmch &= ~((gen < 8 ? 0x1f : 0xff) << (gen < 8 ? 3 : 8));
-
-    /* GMCH is read-only, emulated */
-    pci_set_long(vdev->pdev.config + IGD_GMCH, gmch);
-    pci_set_long(vdev->pdev.wmask + IGD_GMCH, 0);
-    pci_set_long(vdev->emulated_config_bits + IGD_GMCH, ~0);
-
     /*
-     * This must be at address 00:02.0 for us to even onsider enabling
-     * legacy mode.  The vBIOS has dependencies on the PCI bus address.
+     * This must be an Intel VGA device at address 00:02.0 for us to even
+     * consider enabling legacy mode.  The vBIOS has dependencies on the
+     * PCI bus address.
      */
-    if (&vdev->pdev != pci_find_device(pci_device_root_bus(&vdev->pdev),
+    if (!vfio_pci_is(vdev, PCI_VENDOR_ID_INTEL, PCI_ANY_ID) ||
+        !vfio_is_vga(vdev) || nr != 4 ||
+        &vdev->pdev != pci_find_device(pci_device_root_bus(&vdev->pdev),
                                        0, PCI_DEVFN(0x2, 0))) {
         return;
     }
@@ -1425,6 +1394,18 @@ static void vfio_probe_igd_bar4_quirk(VFIOPCIDevice 
*vdev, int nr)
     }
 
     /*
+     * IGD is not a standard, they like to change their specs often.  We
+     * only attempt to support back to SandBridge and we hope that newer
+     * devices maintain compatibility with generation 8.
+     */
+    gen = igd_gen(vdev);
+    if (gen != 6 && gen != 8) {
+        error_report("IGD device %s is unsupported in legacy mode, "
+                     "try SandyBridge or newer", vdev->vbasedev.name);
+        return;
+    }
+
+    /*
      * Most of what we're doing here is to enable the ROM to run, so if
      * there's no ROM, there's no point in setting up this quirk.
      * NB. We only seem to get BIOS ROMs, so a UEFI VM would need CSM support.
@@ -1479,6 +1460,8 @@ static void vfio_probe_igd_bar4_quirk(VFIOPCIDevice 
*vdev, int nr)
         goto out;
     }
 
+    gmch = vfio_pci_read_config(&vdev->pdev, IGD_GMCH, 4);
+
     /*
      * If IGD VGA Disable is clear (expected) and VGA is not already enabled,
      * try to enable it.  Probably shouldn't be using legacy mode without VGA,
@@ -1549,11 +1532,12 @@ static void vfio_probe_igd_bar4_quirk(VFIOPCIDevice 
*vdev, int nr)
      * when IVD (IGD VGA Disable) is clear, but the claim is that it's unused,
      * so let's not waste VM memory for it.
      */
+    gmch &= ~((gen < 8 ? 0x1f : 0xff) << (gen < 8 ? 3 : 8));
+
     if (vdev->igd_gms) {
         if (vdev->igd_gms <= 0x10) {
             gms_mb = vdev->igd_gms * 32;
             gmch |= vdev->igd_gms << (gen < 8 ? 3 : 8);
-            pci_set_long(vdev->pdev.config + IGD_GMCH, gmch);
         } else {
             error_report("Unsupported IGD GMS value 0x%x", vdev->igd_gms);
             vdev->igd_gms = 0;
@@ -1573,6 +1557,11 @@ static void vfio_probe_igd_bar4_quirk(VFIOPCIDevice 
*vdev, int nr)
     fw_cfg_add_file(fw_cfg_find(), "etc/igd-bdsm-size",
                     bdsm_size, sizeof(*bdsm_size));
 
+    /* GMCH is read-only, emulated */
+    pci_set_long(vdev->pdev.config + IGD_GMCH, gmch);
+    pci_set_long(vdev->pdev.wmask + IGD_GMCH, 0);
+    pci_set_long(vdev->emulated_config_bits + IGD_GMCH, ~0);
+
     /* BDSM is read-write, emulated.  The BIOS needs to be able to write it */
     pci_set_long(vdev->pdev.config + IGD_BDSM, 0);
     pci_set_long(vdev->pdev.wmask + IGD_BDSM, ~0);