On Tue, Dec 19, 2023 at 11:32:27PM -0800, Changyuan Lyu wrote:
> On Tue, Dec 19, 2023 at 11:01 PM Michael S. Tsirkin <m...@redhat.com> wrote:
> >
> > This is not a great description. Please describe what the patch does.
>
> Thanks for the feedback! Please see the v3 patch below.
>
> ---8<---
>
> This patch adds the support for feature VIRTIO_PMEM_F_SHMEM_REGION
> (virtio spec v1.2 section 5.19.5.2 [1]). Feature bit
> VIRTIO_PMEM_F_SHMEM_REGION is added to the driver feature
> table.
>
> If the driver feature bit VIRTIO_PMEM_F_SHMEM_REGION is found,
> during probe, virtio pmem ignores the `start` and `size` fields in
> device config and looks for a shared memory region of id 0. The
> physical address range of the pmem is then determined by 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 <changyu...@google.com>
>
> ---
> v3:
> * updated the patch description.
> V2:
> * renamed VIRTIO_PMEM_SHMCAP_ID to VIRTIO_PMEM_SHMEM_REGION_ID
> * fixed the error handling when region 0 does not exist
> ---
> drivers/nvdimm/virtio_pmem.c | 30 ++++++++++++++++++++++++++----
> include/uapi/linux/virtio_pmem.h | 8 ++++++++
> 2 files changed, 34 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> index a92eb172f0e7..8e447c7558cb 100644
> --- a/drivers/nvdimm/virtio_pmem.c
> +++ b/drivers/nvdimm/virtio_pmem.c
> @@ -35,6 +35,8 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
> struct nd_region *nd_region;
> struct virtio_pmem *vpmem;
> struct resource res;
> + struct virtio_shm_region shm_reg;
> + bool have_shm;
> int err = 0;
>
> if (!vdev->config->get) {
> @@ -57,10 +59,24 @@ 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)) {
> + have_shm = virtio_get_shm_region(vdev, &shm_reg,
> + (u8)VIRTIO_PMEM_SHMEM_REGION_ID);
> + if (!have_shm) {
> + dev_err(&vdev->dev, "failed to get shared memory region
> %d\n",
> + VIRTIO_PMEM_SHMEM_REGION_ID);
> + err = -ENXIO;
> + goto out_vq;
Maybe additionally, add a validate callback and clear
VIRTIO_PMEM_F_SHMEM_REGION if VIRTIO_PMEM_SHMEM_REGION_ID is not there.
> + }
> + 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;
> @@ -122,7 +138,13 @@ 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,
> diff --git a/include/uapi/linux/virtio_pmem.h
> b/include/uapi/linux/virtio_pmem.h
> index d676b3620383..c5e49b6e58b1 100644
> --- a/include/uapi/linux/virtio_pmem.h
> +++ b/include/uapi/linux/virtio_pmem.h
> @@ -14,6 +14,14 @@
> #include <linux/virtio_ids.h>
> #include <linux/virtio_config.h>
>
> +/* Feature bits */
> +#define VIRTIO_PMEM_F_SHMEM_REGION 0 /* guest physical address range will be
> + * indicated as shared memory region 0
> + */
Either make this comment shorter to fit in one line, or put the
multi-line comment before the define.
> +
> +/* 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;
> --
> 2.43.0.472.g3155946c3a-goog
