virtio_pmem: support feature SHMEM_REGION

This patch adds the support for feature VIRTIO_PMEM_F_SHMEM_REGION
(virtio spec v1.2 section 5.19.5.2 [1]).

During feature negotiation, if VIRTIO_PMEM_F_SHMEM_REGION is offered
by the device, the driver looks for a shared memory region of id 0.
If it is found, this feature is understood. Otherwise, this feature
bit is cleared.

During probe, if VIRTIO_PMEM_F_SHMEM_REGION has been negotiated,
virtio pmem ignores the `start` and `size` fields in device config
and uses the physical address range of shared memory region 0.

[1] https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-6480002

Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Message-Id: <20231220204906.566922-1-changyuanl@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
index a92eb172f0e7eb9a0feed5a05a7b887066c02ec2..4ceced5cefcf1d40d9eef0817c623bd798a49d79 100644 (file)
--- a/drivers/nvdimm/virtio_pmem.c
+++ b/drivers/nvdimm/virtio_pmem.c
@@ -29,12 +29,27 @@ static int init_vq(struct virtio_pmem *vpmem)
        return 0;
 };
 
+static int virtio_pmem_validate(struct virtio_device *vdev)
+{
+       struct virtio_shm_region shm_reg;
+
+       if (virtio_has_feature(vdev, VIRTIO_PMEM_F_SHMEM_REGION) &&
+               !virtio_get_shm_region(vdev, &shm_reg, (u8)VIRTIO_PMEM_SHMEM_REGION_ID)
+       ) {
+               dev_notice(&vdev->dev, "failed to get shared memory region %d\n",
+                               VIRTIO_PMEM_SHMEM_REGION_ID);
+               __virtio_clear_bit(vdev, VIRTIO_PMEM_F_SHMEM_REGION);
+       }
+       return 0;
+}
+
 static int virtio_pmem_probe(struct virtio_device *vdev)
 {
        struct nd_region_desc ndr_desc = {};
        struct nd_region *nd_region;
        struct virtio_pmem *vpmem;
        struct resource res;
+       struct virtio_shm_region shm_reg;
        int err = 0;
 
        if (!vdev->config->get) {
@@ -57,10 +72,16 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
                goto out_err;
        }
 
-       virtio_cread_le(vpmem->vdev, struct virtio_pmem_config,
-                       start, &vpmem->start);
-       virtio_cread_le(vpmem->vdev, struct virtio_pmem_config,
-                       size, &vpmem->size);
+       if (virtio_has_feature(vdev, VIRTIO_PMEM_F_SHMEM_REGION)) {
+               virtio_get_shm_region(vdev, &shm_reg, (u8)VIRTIO_PMEM_SHMEM_REGION_ID);
+               vpmem->start = shm_reg.addr;
+               vpmem->size = shm_reg.len;
+       } else {
+               virtio_cread_le(vpmem->vdev, struct virtio_pmem_config,
+                               start, &vpmem->start);
+               virtio_cread_le(vpmem->vdev, struct virtio_pmem_config,
+                               size, &vpmem->size);
+       }
 
        res.start = vpmem->start;
        res.end   = vpmem->start + vpmem->size - 1;
@@ -122,10 +143,17 @@ static void virtio_pmem_remove(struct virtio_device *vdev)
        virtio_reset_device(vdev);
 }
 
+static unsigned int features[] = {
+       VIRTIO_PMEM_F_SHMEM_REGION,
+};
+
 static struct virtio_driver virtio_pmem_driver = {
+       .feature_table          = features,
+       .feature_table_size     = ARRAY_SIZE(features),
        .driver.name            = KBUILD_MODNAME,
        .driver.owner           = THIS_MODULE,
        .id_table               = id_table,
+       .validate               = virtio_pmem_validate,
        .probe                  = virtio_pmem_probe,
        .remove                 = virtio_pmem_remove,
 };

diff --git a/include/uapi/linux/virtio_pmem.h b/include/uapi/linux/virtio_pmem.h
index d676b3620383c3cb76be7b4aa3651b1a99e5ded9..ede4f3564977dcd477e386c51c2a73a11dac43a2 100644 (file)
--- a/include/uapi/linux/virtio_pmem.h
+++ b/include/uapi/linux/virtio_pmem.h
@@ -14,6 +14,13 @@
 #include <linux/virtio_ids.h>
 #include <linux/virtio_config.h>
 
+/* Feature bits */
+/* guest physical address range will be indicated as shared memory region 0 */
+#define VIRTIO_PMEM_F_SHMEM_REGION 0
+
+/* shmid of the shared memory region corresponding to the pmem */
+#define VIRTIO_PMEM_SHMEM_REGION_ID 0
+
 struct virtio_pmem_config {
        __le64 start;
        __le64 size;