[Qemu-devel] [RFC PATCH v2] fw/pci: Add support for mapping Intel IGD OpRegion via QEMU

[Alex Williamson <alex.williamson@redhat.com>]

When assigning Intel IGD graphics via QEMU/vfio, the OpRegion for the
device may be exposed as a fw_cfg file.  Allocate space for this, copy
the contents and write the ASL Storage register (0xFC) to point to
this buffer.  NB, it's possible for QEMU to use the write to the ASL
Storage register to map access to the host OpRegion overlapping the
allocated buffer, but we shouldn't care if it does.

References:
kernel vfio opregion support:
https://lkml.org/lkml/2016/2/1/884
QEMU vfio opregion support (revised v2 of 7/7 adds fw_cfg):
https://lists.gnu.org/archive/html/qemu-devel/2016-02/msg00202.html
Gerd's IGD assignment series:
https://lists.gnu.org/archive/html/qemu-devel/2016-01/msg00244.html

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 src/fw/pciinit.c |   30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
index c31c2fa..92170d5 100644
--- a/src/fw/pciinit.c
+++ b/src/fw/pciinit.c
@@ -257,6 +257,32 @@ static void ich9_smbus_setup(struct pci_device *dev, void *arg)
     pci_config_writeb(bdf, ICH9_SMB_HOSTC, ICH9_SMB_HOSTC_HST_EN);
 }
 
+static void intel_igd_opregion_setup(struct pci_device *dev, void *arg)
+{
+    struct romfile_s *file = romfile_find("etc/igd-opregion");
+    void *opregion;
+    u16 bdf = dev->bdf;
+
+    if (!file || !file->size)
+        return;
+
+    opregion = memalign_high(PAGE_SIZE, file->size);
+    if (!opregion) {
+        warn_noalloc();
+        return;
+    }
+
+    if (file->copy(file, opregion, file->size) < 0) {
+        free(opregion);
+        return;
+    }
+
+    pci_config_writel(bdf, 0xFC, cpu_to_le32((u32)opregion));
+
+    dprintf(1, "Intel IGD OpRegion enabled on %02x:%02x.%x\n",
+            pci_bdf_to_bus(bdf), pci_bdf_to_dev(bdf), pci_bdf_to_fn(bdf));
+}
+
 static const struct pci_device_id pci_device_tbl[] = {
     /* PIIX3/PIIX4 PCI to ISA bridge */
     PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371SB_0,
@@ -290,6 +316,10 @@ static const struct pci_device_id pci_device_tbl[] = {
     PCI_DEVICE_CLASS(PCI_VENDOR_ID_APPLE, 0x0017, 0xff00, apple_macio_setup),
     PCI_DEVICE_CLASS(PCI_VENDOR_ID_APPLE, 0x0022, 0xff00, apple_macio_setup),
 
+    /* Intel IGD OpRegion setup */
+    PCI_DEVICE_CLASS(PCI_VENDOR_ID_INTEL, PCI_ANY_ID, PCI_CLASS_DISPLAY_VGA,
+                     intel_igd_opregion_setup),
+
     PCI_DEVICE_END,
 };