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Date: Wed, 27 Dec 2023 10:51:30 +0800
From: Jason Wang <jasowang@...hat.com>
To: Changyuan Lyu <changyuanl@...gle.com>
Cc: mst@...hat.com, dan.j.williams@...el.com, dave.jiang@...el.com,
linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev,
pankaj.gupta.linux@...il.com, virtualization@...ts.linux.dev,
vishal.l.verma@...el.com, xuanzhuo@...ux.alibaba.com
Subject: Re: [PATCH v4] virtio_pmem: support feature SHMEM_REGION
On Thu, Dec 21, 2023 at 4:49 AM Changyuan Lyu <changyuanl@...gle.com> wrote:
>
> Thanks Michael for the feedback!
>
> On Tue, Dec 19, 2023 at 11:44 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > > On Tue, Dec 19, 2023 at 11:32:27PM -0800, Changyuan Lyu wrote:
> > >
> > > + 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.
>
> Done.
>
> > > +/* 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.
>
> Done.
>
> ---8<---
>
> 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@...gle.com>
Acked-by: Jason Wang <jasowang@...hat.com>
Thanks
> ---
> v4:
> * added virtio_pmem_validate callback.
> 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 | 36 ++++++++++++++++++++++++++++----
> include/uapi/linux/virtio_pmem.h | 7 +++++++
> 2 files changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> index a92eb172f0e7..4ceced5cefcf 100644
> --- 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 d676b3620383..ede4f3564977 100644
> --- 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;
> --
> 2.43.0.472.g3155946c3a-goog
>
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