[RFC PATCH v3 11/20] vfio/pci: Use access ops for hardware information queries

[Shameer Kolothum <skolothumtho@nvidia.com>]

AtomicOps and ROM information queries access PCI configuration and ROM
contents. Run these accesses through access ops and keep userspace
copies outside SRCU. Free the capability buffer if the query fails.

A VF's AtomicOps query accesses its PF. If the PF is managed by VFIO and
supports recovery, check its access ops too. Hold the PF's access_lock
and reject queries when it is closed, since its SRCU instance exists
only while open. Other PF drivers retain their existing behavior.

Signed-off-by: Shameer Kolothum <skolothumtho@nvidia.com>
---
 drivers/vfio/pci/vfio_pci_core.c | 82 ++++++++++++++++++++++++--------
 1 file changed, 61 insertions(+), 21 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index fc6b2673be88..da7166669dc7 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1178,6 +1178,33 @@ static int vfio_pci_info_atomic_cap(struct vfio_pci_core_device *vdev,
 	return vfio_info_add_capability(caps, &cap.header, sizeof(cap));
 }
 
+static long vfio_pci_access_atomic_cap_target(struct vfio_pci_core_device *vdev,
+					      void *data)
+{
+	return vfio_pci_info_atomic_cap(vdev, data);
+}
+
+static long vfio_pci_access_atomic_cap(struct vfio_pci_core_device *vdev,
+				       void *data)
+{
+	struct vfio_pci_core_device *pf_vdev = vdev->sriov_pf_core_dev;
+
+	if (!pf_vdev || !pf_vdev->pci_recovery_supported)
+		return vfio_pci_info_atomic_cap(vdev, data);
+
+	/*
+	 * VF AtomicOps queries read the PF's configuration. The PF association
+	 * lasts until VF removal, but its SRCU instance exists only while
+	 * the PF is open.
+	 */
+	guard(mutex)(&pf_vdev->access_lock);
+	if (!pf_vdev->device_open)
+		return -EIO;
+
+	return vfio_pci_core_access(pf_vdev, vfio_pci_access_atomic_cap_target,
+				    data);
+}
+
 static int vfio_pci_ioctl_get_info(struct vfio_pci_core_device *vdev,
 				   struct vfio_device_info __user *arg)
 {
@@ -1209,10 +1236,12 @@ static int vfio_pci_ioctl_get_info(struct vfio_pci_core_device *vdev,
 		return ret;
 	}
 
-	ret = vfio_pci_info_atomic_cap(vdev, &caps);
+	ret = vfio_pci_core_access(vdev, vfio_pci_access_atomic_cap, &caps);
 	if (ret && ret != -ENODEV) {
-		pci_warn(vdev->pdev,
-			 "Failed to setup AtomicOps info capability\n");
+		if (ret != -EIO)
+			pci_warn(vdev->pdev,
+				 "Failed to setup AtomicOps info capability\n");
+		kfree(caps.buf);
 		return ret;
 	}
 
@@ -1235,6 +1264,31 @@ static int vfio_pci_ioctl_get_info(struct vfio_pci_core_device *vdev,
 	return copy_to_user(arg, &info, minsz) ? -EFAULT : 0;
 }
 
+static long vfio_pci_access_rom_info(struct vfio_pci_core_device *vdev,
+				     void *data)
+{
+	struct vfio_region_info *info = data;
+	struct pci_dev *pdev = vdev->pdev;
+	void __iomem *io;
+	size_t size;
+	u16 cmd;
+
+	/*
+	 * Check ROM content is valid. Need to enable memory
+	 * decode for ROM access in pci_map_rom().
+	 */
+	cmd = vfio_pci_memory_lock_and_enable(vdev);
+	io = pci_map_rom(pdev, &size);
+	if (io) {
+		info->flags = VFIO_REGION_INFO_FLAG_READ;
+		/* Report the BAR size, not the ROM size. */
+		info->size = pci_resource_len(pdev, PCI_ROM_RESOURCE);
+		pci_unmap_rom(pdev, io);
+	}
+	vfio_pci_memory_unlock_and_restore(vdev, cmd);
+	return 0;
+}
+
 int vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
 				   struct vfio_region_info *info,
 				   struct vfio_info_cap *caps)
@@ -1272,29 +1326,15 @@ int vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
 
 		break;
 	case VFIO_PCI_ROM_REGION_INDEX: {
-		void __iomem *io;
-		size_t size;
-		u16 cmd;
-
 		info->offset = VFIO_PCI_INDEX_TO_OFFSET(info->index);
 		info->flags = 0;
 		info->size = 0;
 
 		if (pci_resource_start(pdev, PCI_ROM_RESOURCE)) {
-			/*
-			 * Check ROM content is valid. Need to enable memory
-			 * decode for ROM access in pci_map_rom().
-			 */
-			cmd = vfio_pci_memory_lock_and_enable(vdev);
-			io = pci_map_rom(pdev, &size);
-			if (io) {
-				info->flags = VFIO_REGION_INFO_FLAG_READ;
-				/* Report the BAR size, not the ROM size. */
-				info->size = pci_resource_len(pdev,
-							      PCI_ROM_RESOURCE);
-				pci_unmap_rom(pdev, io);
-			}
-			vfio_pci_memory_unlock_and_restore(vdev, cmd);
+			ret = vfio_pci_core_access(vdev, vfio_pci_access_rom_info,
+						   info);
+			if (ret)
+				return ret;
 		} else if (pdev->rom && pdev->romlen) {
 			info->flags = VFIO_REGION_INFO_FLAG_READ;
 			/* Report BAR size as power of two. */
-- 
2.43.0