hisi_acc_vfio_pci: Restrict access to VF dev BAR2 migration region

HiSilicon ACC VF device BAR2 region consists of both functional register
space and migration control register space. Unnecessarily exposing the
migration BAR region to the Guest has the potential to prevent/corrupt
the Guest migration.

Hence, introduce a separate struct vfio_device_ops for migration support
which will override the ioctl/read/write/mmap methods to hide the
migration region and limit the Guest access only to the functional
register space.

This will be used in subsequent patches when we add migration support
to the driver.

Please note that it is OK to export the entire VF BAR if migration is
not supported or required as this cannot affect the PF configurations.

Reviewed-by: Longfang Liu <liulongfang@huawei.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20220308184902.2242-6-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 126 insertions, 0 deletions

diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
index 8129c3457b3b..582ee4fa4109 100644
--- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
+++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
@@ -13,6 +13,119 @@
 #include <linux/vfio.h>
 #include <linux/vfio_pci_core.h>
 
+static int hisi_acc_pci_rw_access_check(struct vfio_device *core_vdev,
+					size_t count, loff_t *ppos,
+					size_t *new_count)
+{
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	struct vfio_pci_core_device *vdev =
+		container_of(core_vdev, struct vfio_pci_core_device, vdev);
+
+	if (index == VFIO_PCI_BAR2_REGION_INDEX) {
+		loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+		resource_size_t end = pci_resource_len(vdev->pdev, index) / 2;
+
+		/* Check if access is for migration control region */
+		if (pos >= end)
+			return -EINVAL;
+
+		*new_count = min(count, (size_t)(end - pos));
+	}
+
+	return 0;
+}
+
+static int hisi_acc_vfio_pci_mmap(struct vfio_device *core_vdev,
+				  struct vm_area_struct *vma)
+{
+	struct vfio_pci_core_device *vdev =
+		container_of(core_vdev, struct vfio_pci_core_device, vdev);
+	unsigned int index;
+
+	index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
+	if (index == VFIO_PCI_BAR2_REGION_INDEX) {
+		u64 req_len, pgoff, req_start;
+		resource_size_t end = pci_resource_len(vdev->pdev, index) / 2;
+
+		req_len = vma->vm_end - vma->vm_start;
+		pgoff = vma->vm_pgoff &
+			((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
+		req_start = pgoff << PAGE_SHIFT;
+
+		if (req_start + req_len > end)
+			return -EINVAL;
+	}
+
+	return vfio_pci_core_mmap(core_vdev, vma);
+}
+
+static ssize_t hisi_acc_vfio_pci_write(struct vfio_device *core_vdev,
+				       const char __user *buf, size_t count,
+				       loff_t *ppos)
+{
+	size_t new_count = count;
+	int ret;
+
+	ret = hisi_acc_pci_rw_access_check(core_vdev, count, ppos, &new_count);
+	if (ret)
+		return ret;
+
+	return vfio_pci_core_write(core_vdev, buf, new_count, ppos);
+}
+
+static ssize_t hisi_acc_vfio_pci_read(struct vfio_device *core_vdev,
+				      char __user *buf, size_t count,
+				      loff_t *ppos)
+{
+	size_t new_count = count;
+	int ret;
+
+	ret = hisi_acc_pci_rw_access_check(core_vdev, count, ppos, &new_count);
+	if (ret)
+		return ret;
+
+	return vfio_pci_core_read(core_vdev, buf, new_count, ppos);
+}
+
+static long hisi_acc_vfio_pci_ioctl(struct vfio_device *core_vdev, unsigned int cmd,
+				    unsigned long arg)
+{
+	if (cmd == VFIO_DEVICE_GET_REGION_INFO) {
+		struct vfio_pci_core_device *vdev =
+			container_of(core_vdev, struct vfio_pci_core_device, vdev);
+		struct pci_dev *pdev = vdev->pdev;
+		struct vfio_region_info info;
+		unsigned long minsz;
+
+		minsz = offsetofend(struct vfio_region_info, offset);
+
+		if (copy_from_user(&info, (void __user *)arg, minsz))
+			return -EFAULT;
+
+		if (info.argsz < minsz)
+			return -EINVAL;
+
+		if (info.index == VFIO_PCI_BAR2_REGION_INDEX) {
+			info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
+
+			/*
+			 * ACC VF dev BAR2 region consists of both functional
+			 * register space and migration control register space.
+			 * Report only the functional region to Guest.
+			 */
+			info.size = pci_resource_len(pdev, info.index) / 2;
+
+			info.flags = VFIO_REGION_INFO_FLAG_READ |
+					VFIO_REGION_INFO_FLAG_WRITE |
+					VFIO_REGION_INFO_FLAG_MMAP;
+
+			return copy_to_user((void __user *)arg, &info, minsz) ?
+					    -EFAULT : 0;
+		}
+	}
+	return vfio_pci_core_ioctl(core_vdev, cmd, arg);
+}
+
 static int hisi_acc_vfio_pci_open_device(struct vfio_device *core_vdev)
 {
 	struct vfio_pci_core_device *vdev =
@@ -28,6 +141,19 @@ static int hisi_acc_vfio_pci_open_device(struct vfio_device *core_vdev)
 	return 0;
 }
 
+static const struct vfio_device_ops hisi_acc_vfio_pci_migrn_ops = {
+	.name = "hisi-acc-vfio-pci-migration",
+	.open_device = hisi_acc_vfio_pci_open_device,
+	.close_device = vfio_pci_core_close_device,
+	.ioctl = hisi_acc_vfio_pci_ioctl,
+	.device_feature = vfio_pci_core_ioctl_feature,
+	.read = hisi_acc_vfio_pci_read,
+	.write = hisi_acc_vfio_pci_write,
+	.mmap = hisi_acc_vfio_pci_mmap,
+	.request = vfio_pci_core_request,
+	.match = vfio_pci_core_match,
+};
+
 static const struct vfio_device_ops hisi_acc_vfio_pci_ops = {
 	.name = "hisi-acc-vfio-pci",
 	.open_device = hisi_acc_vfio_pci_open_device,