[Qemu-devel] [RFC PATCH 1/2] qemu vfio-pci: Add support for VGA MMIO and I/O port access

[Alex Williamson]

Most VGA cards need some kind of quirk to fully operate since they
hide backdoors to get to other registers outside of PCI config space
within the registers, but this provides the base infrastructure.  If
we could identity map PCI resources for assigned devices we would need
a lot fewer quirks.

To enable this, use a kernel side vfio-pci driver that incorporates
VGA support (patches posted), and use the -vga none option and add the
x-vga=on option for the vfio-pci device.  The "x-" denotes this as an
experimental feature.  You may also need to use a cached copy of the
VGA BIOS for your device, passing it to vfio-pci using the romfile=
option.

Signed-off-by: Alex Williamson <address@hidden>
---
 hw/vfio_pci.c |  174 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 174 insertions(+)

diff --git a/hw/vfio_pci.c b/hw/vfio_pci.c
index c51ae67..f05a4aa 100644
--- a/hw/vfio_pci.c
+++ b/hw/vfio_pci.c
@@ -59,6 +59,15 @@ typedef struct VFIOBAR {
     uint8_t nr; /* cache the BAR number for debug */
 } VFIOBAR;
 
+typedef struct VFIOLegacyIO {
+    off_t fd_offset;
+    int fd;
+    MemoryRegion mem;
+    off_t region_offset;
+    size_t size;
+    uint32_t flags;
+} VFIOLegacyIO;
+
 typedef struct VFIOINTx {
     bool pending; /* interrupt pending */
     bool kvm_accel; /* set when QEMU bypass through KVM enabled */
@@ -126,10 +135,15 @@ typedef struct VFIODevice {
     int nr_vectors; /* Number of MSI/MSIX vectors currently in use */
     int interrupt; /* Current interrupt type */
     VFIOBAR bars[PCI_NUM_REGIONS - 1]; /* No ROM */
+    VFIOLegacyIO vga[3]; /* 0xa0000, 0x3b0, 0x3c0 */
     PCIHostDeviceAddress host;
     QLIST_ENTRY(VFIODevice) next;
     struct VFIOGroup *group;
+    uint32_t features;
+#define VFIO_FEATURE_ENABLE_VGA_BIT 0
+#define VFIO_FEATURE_ENABLE_VGA (1 << VFIO_FEATURE_ENABLE_VGA_BIT)
     bool reset_works;
+    bool has_vga;
 } VFIODevice;
 
 typedef struct VFIOGroup {
@@ -957,6 +971,87 @@ static const MemoryRegionOps vfio_bar_ops = {
     .endianness = DEVICE_LITTLE_ENDIAN,
 };
 
+static void vfio_legacy_write(void *opaque, hwaddr addr,
+                              uint64_t data, unsigned size)
+{
+    VFIOLegacyIO *io = opaque;
+    union {
+        uint8_t byte;
+        uint16_t word;
+        uint32_t dword;
+        uint64_t qword;
+    } buf;
+    off_t offset = io->fd_offset + io->region_offset + addr;
+
+    switch (size) {
+    case 1:
+        buf.byte = data;
+        break;
+    case 2:
+        buf.word = cpu_to_le16(data);
+        break;
+    case 4:
+        buf.dword = cpu_to_le32(data);
+        break;
+    default:
+        hw_error("vfio: unsupported write size, %d bytes\n", size);
+        break;
+    }
+
+    if (pwrite(io->fd, &buf, size, offset) != size) {
+        error_report("%s(,0x%"HWADDR_PRIx", 0x%"PRIx64", %d) failed: %m\n",
+                     __func__, io->region_offset + addr, data, size);
+    }
+
+    DPRINTF("%s(0x%"HWADDR_PRIx", 0x%"PRIx64", %d)\n",
+            __func__, io->region_offset + addr, data, size);
+}
+
+static uint64_t vfio_legacy_read(void *opaque, hwaddr addr, unsigned size)
+{
+    VFIOLegacyIO *io = opaque;
+    union {
+        uint8_t byte;
+        uint16_t word;
+        uint32_t dword;
+        uint64_t qword;
+    } buf;
+    uint64_t data = 0;
+    off_t offset = io->fd_offset + io->region_offset + addr;
+
+    if (pread(io->fd, &buf, size, offset) != size) {
+        error_report("%s(,0x%"HWADDR_PRIx", %d) failed: %m\n",
+                     __func__, io->region_offset + addr, size);
+        return (uint64_t)-1;
+    }
+
+    switch (size) {
+    case 1:
+        data = buf.byte;
+        break;
+    case 2:
+        data = le16_to_cpu(buf.word);
+        break;
+    case 4:
+        data = le32_to_cpu(buf.dword);
+        break;
+    default:
+        hw_error("vfio: unsupported read size, %d bytes\n", size);
+        break;
+    }
+
+    DPRINTF("%s(0x%"HWADDR_PRIx", %d) = 0x%"PRIx64"\n",
+            __func__, io->region_offset + addr, size, data);
+
+    return data;
+}
+
+static const MemoryRegionOps vfio_legacy_ops = {
+    .read = vfio_legacy_read,
+    .write = vfio_legacy_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+};
+
 /*
  * PCI config space
  */
@@ -1497,6 +1592,26 @@ static void vfio_map_bars(VFIODevice *vdev)
     for (i = 0; i < PCI_ROM_SLOT; i++) {
         vfio_map_bar(vdev, i);
     }
+
+    if (vdev->has_vga && (vdev->features & VFIO_FEATURE_ENABLE_VGA)) {
+        memory_region_init_io(&vdev->vga[0].mem, &vfio_legacy_ops,
+                              &vdev->vga[0], "address@hidden",
+                              0xc0000 - 0xa0000);
+        memory_region_add_subregion_overlap(pci_address_space(&vdev->pdev),
+                                            0xa0000, &vdev->vga[0].mem, 1);
+
+        memory_region_init_io(&vdev->vga[1].mem, &vfio_legacy_ops,
+                              &vdev->vga[1], "address@hidden",
+                              0x3bc - 0x3b0);
+        memory_region_add_subregion_overlap(pci_address_space_io(&vdev->pdev),
+                                            0x3b0, &vdev->vga[1].mem, 1);
+
+        memory_region_init_io(&vdev->vga[2].mem, &vfio_legacy_ops,
+                              &vdev->vga[2], "address@hidden",
+                              0x3e0 - 0x3c0);
+        memory_region_add_subregion_overlap(pci_address_space_io(&vdev->pdev),
+                                            0x3c0, &vdev->vga[2].mem, 1);
+    }
 }
 
 static void vfio_unmap_bars(VFIODevice *vdev)
@@ -1506,6 +1621,20 @@ static void vfio_unmap_bars(VFIODevice *vdev)
     for (i = 0; i < PCI_ROM_SLOT; i++) {
         vfio_unmap_bar(vdev, i);
     }
+
+    if (vdev->has_vga && (vdev->features & VFIO_FEATURE_ENABLE_VGA)) {
+        memory_region_del_subregion(pci_address_space(&vdev->pdev),
+                                    &vdev->vga[0].mem);
+        memory_region_destroy(&vdev->vga[0].mem);
+
+        memory_region_del_subregion(pci_address_space_io(&vdev->pdev),
+                                    &vdev->vga[1].mem);
+        memory_region_destroy(&vdev->vga[1].mem);
+
+        memory_region_del_subregion(pci_address_space_io(&vdev->pdev),
+                                    &vdev->vga[2].mem);
+        memory_region_destroy(&vdev->vga[2].mem);
+    }
 }
 
 /*
@@ -1901,6 +2030,49 @@ static int vfio_get_device(VFIOGroup *group, const char 
*name, VFIODevice *vdev)
     vdev->config_size = reg_info.size;
     vdev->config_offset = reg_info.offset;
 
+    if (dev_info.flags & VFIO_DEVICE_FLAGS_PCI_VGA) {
+        struct vfio_region_info mmio_info, io_info;
+
+        if (!(dev_info.flags & VFIO_DEVICE_FLAGS_PCI_LEGACY_MMIO) ||
+            !(dev_info.flags & VFIO_DEVICE_FLAGS_PCI_LEGACY_IOPORT)) {
+            error_report("vfio: Device reports VGA support but not legacy "
+                         "MMIO or I/O port ranges.  VGA support disabled.\n");
+            goto error;
+        }
+
+        mmio_info.argsz = io_info.argsz = sizeof(struct vfio_region_info);
+        mmio_info.index = VFIO_PCI_LEGACY_MMIO_REGION_INDEX;
+        io_info.index = VFIO_PCI_LEGACY_IOPORT_REGION_INDEX;
+
+        ret = ioctl(vdev->fd, VFIO_DEVICE_GET_REGION_INFO, &mmio_info);
+        if (ret) {
+            error_report("vfio: Unable to access VGA MMIO resources: %m\n");
+            goto error;
+        }
+
+        vdev->vga[0].flags = mmio_info.flags;
+        vdev->vga[0].size = mmio_info.size;
+        vdev->vga[0].fd_offset = mmio_info.offset;
+        vdev->vga[0].fd = vdev->fd;
+        vdev->vga[0].region_offset = 0xa0000;
+
+        ret = ioctl(vdev->fd, VFIO_DEVICE_GET_REGION_INFO, &io_info);
+        if (ret) {
+            error_report("vfio: Unable to access VGA IOPORT resources: %m\n");
+            goto error;
+        }
+
+        vdev->vga[1].flags = vdev->vga[2].flags = io_info.flags;
+        vdev->vga[1].size = vdev->vga[2].size = io_info.size;
+        vdev->vga[1].fd_offset = vdev->vga[2].fd_offset = io_info.offset;
+        vdev->vga[1].fd = vdev->vga[2].fd = vdev->fd;
+
+        vdev->vga[1].region_offset = 0x3b0;
+        vdev->vga[2].region_offset = 0x3c0;
+
+        vdev->has_vga = true;
+    }
+
 error:
     if (ret) {
         QLIST_REMOVE(vdev, next);
@@ -2095,6 +2267,8 @@ static Property vfio_pci_dev_properties[] = {
     DEFINE_PROP_PCI_HOST_DEVADDR("host", VFIODevice, host),
     DEFINE_PROP_UINT32("x-intx-mmap-timeout-ms", VFIODevice,
                        intx.mmap_timeout, 1100),
+    DEFINE_PROP_BIT("x-vga", VFIODevice, features,
+                    VFIO_FEATURE_ENABLE_VGA_BIT, false),
     /*
      * TODO - support passed fds... is this necessary?
      * DEFINE_PROP_STRING("vfiofd", VFIODevice, vfiofd_name),