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SubjectRe: [PATCH 04/20] virtio: Implement get_shm_region for PCI transport
On Wed, Mar 04, 2020 at 11:58:29AM -0500, Vivek Goyal wrote:
> From: Sebastien Boeuf <sebastien.boeuf@intel.com>
>
> On PCI the shm regions are found using capability entries;
> find a region by searching for the capability.
>
> Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: kbuild test robot <lkp@intel.com>
> ---
> drivers/virtio/virtio_pci_modern.c | 107 +++++++++++++++++++++++++++++
> include/uapi/linux/virtio_pci.h | 11 ++-
> 2 files changed, 117 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 7abcc50838b8..52f179411015 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -443,6 +443,111 @@ static void del_vq(struct virtio_pci_vq_info *info)
> vring_del_virtqueue(vq);
> }
>
> +static int virtio_pci_find_shm_cap(struct pci_dev *dev,
> + u8 required_id,
> + u8 *bar, u64 *offset, u64 *len)
> +{
> + int pos;
> +
> + for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR);
> + pos > 0;
> + pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) {
> + u8 type, cap_len, id;
> + u32 tmp32;
> + u64 res_offset, res_length;
> +
> + pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
> + cfg_type),
> + &type);
> + if (type != VIRTIO_PCI_CAP_SHARED_MEMORY_CFG)
> + continue;
> +
> + pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
> + cap_len),
> + &cap_len);
> + if (cap_len != sizeof(struct virtio_pci_cap64)) {
> + printk(KERN_ERR "%s: shm cap with bad size offset: %d size: %d\n",
> + __func__, pos, cap_len);
> + continue;
> + }
> +
> + pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
> + id),
> + &id);
> + if (id != required_id)
> + continue;
> +
> + /* Type, and ID match, looks good */
> + pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
> + bar),
> + bar);
> +
> + /* Read the lower 32bit of length and offset */
> + pci_read_config_dword(dev, pos + offsetof(struct virtio_pci_cap, offset),
> + &tmp32);
> + res_offset = tmp32;
> + pci_read_config_dword(dev, pos + offsetof(struct virtio_pci_cap, length),
> + &tmp32);
> + res_length = tmp32;
> +
> + /* and now the top half */
> + pci_read_config_dword(dev,
> + pos + offsetof(struct virtio_pci_cap64,
> + offset_hi),
> + &tmp32);
> + res_offset |= ((u64)tmp32) << 32;
> + pci_read_config_dword(dev,
> + pos + offsetof(struct virtio_pci_cap64,
> + length_hi),
> + &tmp32);
> + res_length |= ((u64)tmp32) << 32;
> +
> + *offset = res_offset;
> + *len = res_length;
> +
> + return pos;
> + }
> + return 0;
> +}
> +
> +static bool vp_get_shm_region(struct virtio_device *vdev,
> + struct virtio_shm_region *region, u8 id)
> +{
> + struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> + struct pci_dev *pci_dev = vp_dev->pci_dev;
> + u8 bar;
> + u64 offset, len;
> + phys_addr_t phys_addr;
> + size_t bar_len;
> + int ret;
> +
> + if (!virtio_pci_find_shm_cap(pci_dev, id, &bar, &offset, &len)) {
> + return false;
> + }
> +
> + ret = pci_request_region(pci_dev, bar, "virtio-pci-shm");
> + if (ret < 0) {
> + dev_err(&pci_dev->dev, "%s: failed to request BAR\n",
> + __func__);
> + return false;
> + }
> +
> + phys_addr = pci_resource_start(pci_dev, bar);
> + bar_len = pci_resource_len(pci_dev, bar);
> +
> + if (offset + len > bar_len) {
> + dev_err(&pci_dev->dev,
> + "%s: bar shorter than cap offset+len\n",
> + __func__);
> + return false;
> + }
> +

Something wrong with indentation here.
Also as long as you are validating things, it's worth checking
offset + len does not overflow.

> + region->len = len;
> + region->addr = (u64) phys_addr + offset;
> +
> + return true;
> +}
> +
> static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
> .get = NULL,
> .set = NULL,
> @@ -457,6 +562,7 @@ static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
> .bus_name = vp_bus_name,
> .set_vq_affinity = vp_set_vq_affinity,
> .get_vq_affinity = vp_get_vq_affinity,
> + .get_shm_region = vp_get_shm_region,
> };
>
> static const struct virtio_config_ops virtio_pci_config_ops = {
> @@ -473,6 +579,7 @@ static const struct virtio_config_ops virtio_pci_config_ops = {
> .bus_name = vp_bus_name,
> .set_vq_affinity = vp_set_vq_affinity,
> .get_vq_affinity = vp_get_vq_affinity,
> + .get_shm_region = vp_get_shm_region,
> };
>
> /**
> diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
> index 90007a1abcab..fe9f43680a1d 100644
> --- a/include/uapi/linux/virtio_pci.h
> +++ b/include/uapi/linux/virtio_pci.h
> @@ -113,6 +113,8 @@
> #define VIRTIO_PCI_CAP_DEVICE_CFG 4
> /* PCI configuration access */
> #define VIRTIO_PCI_CAP_PCI_CFG 5
> +/* Additional shared memory capability */
> +#define VIRTIO_PCI_CAP_SHARED_MEMORY_CFG 8
>
> /* This is the PCI capability header: */
> struct virtio_pci_cap {
> @@ -121,11 +123,18 @@ struct virtio_pci_cap {
> __u8 cap_len; /* Generic PCI field: capability length */
> __u8 cfg_type; /* Identifies the structure. */
> __u8 bar; /* Where to find it. */
> - __u8 padding[3]; /* Pad to full dword. */
> + __u8 id; /* Multiple capabilities of the same type */
> + __u8 padding[2]; /* Pad to full dword. */
> __le32 offset; /* Offset within bar. */
> __le32 length; /* Length of the structure, in bytes. */
> };
>
> +struct virtio_pci_cap64 {
> + struct virtio_pci_cap cap;
> + __le32 offset_hi; /* Most sig 32 bits of offset */
> + __le32 length_hi; /* Most sig 32 bits of length */
> +};
> +
> struct virtio_pci_notify_cap {
> struct virtio_pci_cap cap;
> __le32 notify_off_multiplier; /* Multiplier for queue_notify_off. */
> --
> 2.20.1

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