vfio/pci: Intel IGD host and LCP bridge config space access

Provide read-only access to PCI config space of the PCI host bridge
and LPC bridge through device specific regions.  This may be used to
configure a VM with matching register contents to satisfy driver
requirements.  Providing this through the vfio file descriptor removes
an additional userspace requirement for access through pci-sysfs and
removes the CAP_SYS_ADMIN requirement that doesn't appear to apply to
the specific devices we're accessing.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

3 files changed, 183 insertions, 7 deletions

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index cb2624db37d8..74a375297494 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -111,6 +111,7 @@ static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
 }
 
 static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev);
+static void vfio_pci_disable(struct vfio_pci_device *vdev);
 
 static int vfio_pci_enable(struct vfio_pci_device *vdev)
 {
@@ -170,10 +171,16 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
                 vdev->has_vga = true;
 
 
-        if (vfio_pci_is_vga(pdev) && pdev->vendor == PCI_VENDOR_ID_INTEL) {
-                if (vfio_pci_igd_opregion_init(vdev) == 0)
-                        dev_info(&pdev->dev,
-                                 "Intel IGD OpRegion support enabled\n");
+        if (vfio_pci_is_vga(pdev) &&
+            pdev->vendor == PCI_VENDOR_ID_INTEL &&
+            IS_ENABLED(CONFIG_VFIO_PCI_IGD)) {
+                ret = vfio_pci_igd_init(vdev);
+                if (ret) {
+                        dev_warn(&vdev->pdev->dev,
+                                 "Failed to setup Intel IGD regions\n");
+                        vfio_pci_disable(vdev);
+                        return ret;
+                }
         }
 
         return 0;
diff --git a/drivers/vfio/pci/vfio_pci_igd.c b/drivers/vfio/pci/vfio_pci_igd.c
index 3b6a6f7b367b..6394b168ef29 100644
--- a/drivers/vfio/pci/vfio_pci_igd.c
+++ b/drivers/vfio/pci/vfio_pci_igd.c
@@ -55,7 +55,7 @@ static const struct vfio_pci_regops vfio_pci_igd_regops = {
         .release        = vfio_pci_igd_release,
 };
 
-int vfio_pci_igd_opregion_init(struct vfio_pci_device *vdev)
+static int vfio_pci_igd_opregion_init(struct vfio_pci_device *vdev)
 {
         __le32 *dwordp = (__le32 *)(vdev->vconfig + OPREGION_PCI_ADDR);
         u32 addr, size;
@@ -109,3 +109,172 @@ int vfio_pci_igd_opregion_init(struct vfio_pci_device *vdev)
 
         return ret;
 }
+
+static size_t vfio_pci_igd_cfg_rw(struct vfio_pci_device *vdev,
+                                  char __user *buf, size_t count, loff_t *ppos,
+                                  bool iswrite)
+{
+        unsigned int i = VFIO_PCI_OFFSET_TO_INDEX(*ppos) - VFIO_PCI_NUM_REGIONS;
+        struct pci_dev *pdev = vdev->region[i].data;
+        loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+        size_t size;
+        int ret;
+
+        if (pos >= vdev->region[i].size || iswrite)
+                return -EINVAL;
+
+        size = count = min(count, (size_t)(vdev->region[i].size - pos));
+
+        if ((pos & 1) && size) {
+                u8 val;
+
+                ret = pci_user_read_config_byte(pdev, pos, &val);
+                if (ret)
+                        return pcibios_err_to_errno(ret);
+
+                if (copy_to_user(buf + count - size, &val, 1))
+                        return -EFAULT;
+
+                pos++;
+                size--;
+        }
+
+        if ((pos & 3) && size > 2) {
+                u16 val;
+
+                ret = pci_user_read_config_word(pdev, pos, &val);
+                if (ret)
+                        return pcibios_err_to_errno(ret);
+
+                val = cpu_to_le16(val);
+                if (copy_to_user(buf + count - size, &val, 2))
+                        return -EFAULT;
+
+                pos += 2;
+                size -= 2;
+        }
+
+        while (size > 3) {
+                u32 val;
+
+                ret = pci_user_read_config_dword(pdev, pos, &val);
+                if (ret)
+                        return pcibios_err_to_errno(ret);
+
+                val = cpu_to_le32(val);
+                if (copy_to_user(buf + count - size, &val, 4))
+                        return -EFAULT;
+
+                pos += 4;
+                size -= 4;
+        }
+
+        while (size >= 2) {
+                u16 val;
+
+                ret = pci_user_read_config_word(pdev, pos, &val);
+                if (ret)
+                        return pcibios_err_to_errno(ret);
+
+                val = cpu_to_le16(val);
+                if (copy_to_user(buf + count - size, &val, 2))
+                        return -EFAULT;
+
+                pos += 2;
+                size -= 2;
+        }
+
+        while (size) {
+                u8 val;
+
+                ret = pci_user_read_config_byte(pdev, pos, &val);
+                if (ret)
+                        return pcibios_err_to_errno(ret);
+
+                if (copy_to_user(buf + count - size, &val, 1))
+                        return -EFAULT;
+
+                pos++;
+                size--;
+        }
+
+        *ppos += count;
+
+        return count;
+}
+
+static void vfio_pci_igd_cfg_release(struct vfio_pci_device *vdev,
+                                     struct vfio_pci_region *region)
+{
+        struct pci_dev *pdev = region->data;
+
+        pci_dev_put(pdev);
+}
+
+static const struct vfio_pci_regops vfio_pci_igd_cfg_regops = {
+        .rw             = vfio_pci_igd_cfg_rw,
+        .release        = vfio_pci_igd_cfg_release,
+};
+
+static int vfio_pci_igd_cfg_init(struct vfio_pci_device *vdev)
+{
+        struct pci_dev *host_bridge, *lpc_bridge;
+        int ret;
+
+        host_bridge = pci_get_domain_bus_and_slot(0, 0, PCI_DEVFN(0, 0));
+        if (!host_bridge)
+                return -ENODEV;
+
+        if (host_bridge->vendor != PCI_VENDOR_ID_INTEL ||
+            host_bridge->class != (PCI_CLASS_BRIDGE_HOST << 8)) {
+                pci_dev_put(host_bridge);
+                return -EINVAL;
+        }
+
+        ret = vfio_pci_register_dev_region(vdev,
+                PCI_VENDOR_ID_INTEL | VFIO_REGION_TYPE_PCI_VENDOR_TYPE,
+                VFIO_REGION_SUBTYPE_INTEL_IGD_HOST_CFG,
+                &vfio_pci_igd_cfg_regops, host_bridge->cfg_size,
+                VFIO_REGION_INFO_FLAG_READ, host_bridge);
+        if (ret) {
+                pci_dev_put(host_bridge);
+                return ret;
+        }
+
+        lpc_bridge = pci_get_domain_bus_and_slot(0, 0, PCI_DEVFN(0x1f, 0));
+        if (!lpc_bridge)
+                return -ENODEV;
+
+        if (lpc_bridge->vendor != PCI_VENDOR_ID_INTEL ||
+            lpc_bridge->class != (PCI_CLASS_BRIDGE_ISA << 8)) {
+                pci_dev_put(lpc_bridge);
+                return -EINVAL;
+        }
+
+        ret = vfio_pci_register_dev_region(vdev,
+                PCI_VENDOR_ID_INTEL | VFIO_REGION_TYPE_PCI_VENDOR_TYPE,
+                VFIO_REGION_SUBTYPE_INTEL_IGD_LPC_CFG,
+                &vfio_pci_igd_cfg_regops, lpc_bridge->cfg_size,
+                VFIO_REGION_INFO_FLAG_READ, lpc_bridge);
+        if (ret) {
+                pci_dev_put(lpc_bridge);
+                return ret;
+        }
+
+        return 0;
+}
+
+int vfio_pci_igd_init(struct vfio_pci_device *vdev)
+{
+        int ret;
+
+        ret = vfio_pci_igd_opregion_init(vdev);
+        if (ret)
+                return ret;
+
+        ret = vfio_pci_igd_cfg_init(vdev);
+        if (ret)
+                return ret;
+
+        return 0;
+}
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 19f7699ac699..8a7d546d18a0 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -123,9 +123,9 @@ extern int vfio_pci_register_dev_region(struct vfio_pci_device *vdev,
                                         const struct vfio_pci_regops *ops,
                                         size_t size, u32 flags, void *data);
 #ifdef CONFIG_VFIO_PCI_IGD
-extern int vfio_pci_igd_opregion_init(struct vfio_pci_device *vdev);
+extern int vfio_pci_igd_init(struct vfio_pci_device *vdev);
 #else
-static inline int vfio_pci_igd_opregion_init(struct vfio_pci_device *vdev)
+static inline int vfio_pci_igd_init(struct vfio_pci_device *vdev)
 {
         return -ENODEV;
 }