On Fri, Jun 28, 2024 at 04:57:07PM +0200, Albert Esteve wrote: > The frontend can use this command to retrieve > VIRTIO Shared Memory Regions configuration from > the backend. The response contains the number of > shared memory regions, their size, and shmid. > > This is useful when the frontend is unaware of > specific backend type and configuration, > for example, in the `vhost-user-device` case. > > Signed-off-by: Albert Esteve <aest...@redhat.com> > --- > docs/interop/vhost-user.rst | 31 +++++++++++++++++++++++ > hw/virtio/vhost-user.c | 42 +++++++++++++++++++++++++++++++ > include/hw/virtio/vhost-backend.h | 6 +++++ > include/hw/virtio/vhost-user.h | 1 + > 4 files changed, 80 insertions(+) > > diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst > index d52ba719d5..51f01d1d84 100644 > --- a/docs/interop/vhost-user.rst > +++ b/docs/interop/vhost-user.rst > @@ -348,6 +348,19 @@ Device state transfer parameters > In the future, additional phases might be added e.g. to allow > iterative migration while the device is running. > > +VIRTIO Shared Memory Region configuration > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > ++-------------+---------+------------+----+------------+ > +| num regions | padding | mem size 0 | .. | mem size 7 | > ++-------------+---------+------------+----+------------+
8 regions may not be enough. The max according to the VIRTIO spec is
256 because virtio-pci uses an 8-bit cap.id field for the shmid. I think
the maximum number should be 256 here.
(I haven't checked the QEMU vhost-user code to see whether it's
reasonable to hardcode to 256 or some logic if needed to dynamically
size the buffer depending on the "num regions" field.)
> +
> +:num regions: a 32-bit number of regions
> +
> +:padding: 32-bit
> +
> +:mem size: 64-bit size of VIRTIO Shared Memory Region
> +
> C structure
> -----------
>
> @@ -369,6 +382,10 @@ In QEMU the vhost-user message is implemented with the
> following struct:
> VhostUserConfig config;
> VhostUserVringArea area;
> VhostUserInflight inflight;
> + VhostUserShared object;
> + VhostUserTransferDeviceState transfer_state;
> + VhostUserMMap mmap;
Why are these added by this patch? Please add them in the same patch
where they are introduced.
> + VhostUserShMemConfig shmem;
> };
> } QEMU_PACKED VhostUserMsg;
>
> @@ -1051,6 +1068,7 @@ Protocol features
> #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17
> #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18
> #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19
> + #define VHOST_USER_PROTOCOL_F_SHMEM 20
>
> Front-end message types
> -----------------------
> @@ -1725,6 +1743,19 @@ Front-end message types
> Using this function requires prior negotiation of the
> ``VHOST_USER_PROTOCOL_F_DEVICE_STATE`` feature.
>
> +``VHOST_USER_GET_SHMEM_CONFIG``
> + :id: 44
> + :equivalent ioctl: N/A
> + :request payload: N/A
> + :reply payload: ``struct VhostUserShMemConfig``
> +
> + When the ``VHOST_USER_PROTOCOL_F_SHMEM`` protocol feature has been
> + successfully negotiated, this message can be submitted by the front-end
> + to gather the VIRTIO Shared Memory Region configuration. Back-end will
> respond
> + with the number of VIRTIO Shared Memory Regions it requires, and each
> shared memory
> + region size in an array. The shared memory IDs are represented by the index
> + of the array.
Is the information returned by SHMEM_CONFIG valid and unchanged for the
entire lifetime of the vhost-user connection?
I think the answer is yes because the enumeration that virtio-pci and
virtio-mmio transports support is basically a one-time operation at
driver startup and it is static (Shared Memory Regions do not appear or
go away at runtime). Please be explicit how VHOST_USER_GET_SHMEM_CONFIG
is intended to be used.
> +
> Back-end message types
> ----------------------
>
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 7ee8a472c6..57406dc8b4 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -104,6 +104,7 @@ typedef enum VhostUserRequest {
> VHOST_USER_GET_SHARED_OBJECT = 41,
> VHOST_USER_SET_DEVICE_STATE_FD = 42,
> VHOST_USER_CHECK_DEVICE_STATE = 43,
> + VHOST_USER_GET_SHMEM_CONFIG = 44,
> VHOST_USER_MAX
> } VhostUserRequest;
>
> @@ -138,6 +139,12 @@ typedef struct VhostUserMemRegMsg {
> VhostUserMemoryRegion region;
> } VhostUserMemRegMsg;
>
> +typedef struct VhostUserShMemConfig {
> + uint32_t nregions;
> + uint32_t padding;
> + uint64_t memory_sizes[VHOST_MEMORY_BASELINE_NREGIONS];
> +} VhostUserShMemConfig;
> +
> typedef struct VhostUserLog {
> uint64_t mmap_size;
> uint64_t mmap_offset;
> @@ -245,6 +252,7 @@ typedef union {
> VhostUserShared object;
> VhostUserTransferDeviceState transfer_state;
> VhostUserMMap mmap;
> + VhostUserShMemConfig shmem;
> } VhostUserPayload;
>
> typedef struct VhostUserMsg {
> @@ -3136,6 +3144,39 @@ static int vhost_user_check_device_state(struct
> vhost_dev *dev, Error **errp)
> return 0;
> }
>
> +static int vhost_user_get_shmem_config(struct vhost_dev *dev,
> + int *nregions,
> + uint64_t *memory_sizes,
> + Error **errp)
> +{
> + int ret;
> + VhostUserMsg msg = {
> + .hdr.request = VHOST_USER_GET_SHMEM_CONFIG,
> + .hdr.flags = VHOST_USER_VERSION,
> + };
> +
> + if (!virtio_has_feature(dev->protocol_features,
> + VHOST_USER_PROTOCOL_F_SHMEM)) {
> + return 0;
> + }
> +
> + ret = vhost_user_write(dev, &msg, NULL, 0);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + ret = vhost_user_read(dev, &msg);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + *nregions = msg.payload.shmem.nregions;
Missing input validation from the untrusted vhost-user backend. nregions
may be out of range.
> + memcpy(memory_sizes,
> + &msg.payload.shmem.memory_sizes,
> + sizeof(uint64_t) * VHOST_MEMORY_BASELINE_NREGIONS);
> + return 0;
> +}
> +
> const VhostOps user_ops = {
> .backend_type = VHOST_BACKEND_TYPE_USER,
> .vhost_backend_init = vhost_user_backend_init,
> @@ -3174,4 +3215,5 @@ const VhostOps user_ops = {
> .vhost_supports_device_state = vhost_user_supports_device_state,
> .vhost_set_device_state_fd = vhost_user_set_device_state_fd,
> .vhost_check_device_state = vhost_user_check_device_state,
> + .vhost_get_shmem_config = vhost_user_get_shmem_config,
> };
> diff --git a/include/hw/virtio/vhost-backend.h
> b/include/hw/virtio/vhost-backend.h
> index 70c2e8ffee..f9c2955420 100644
> --- a/include/hw/virtio/vhost-backend.h
> +++ b/include/hw/virtio/vhost-backend.h
> @@ -159,6 +159,11 @@ typedef int (*vhost_set_device_state_fd_op)(struct
> vhost_dev *dev,
> int *reply_fd,
> Error **errp);
> typedef int (*vhost_check_device_state_op)(struct vhost_dev *dev, Error
> **errp);
> +typedef int (*vhost_get_shmem_config_op)(struct vhost_dev *dev,
> + int *nregions,
> + uint64_t *memory_sizes,
> + Error **errp);
> +
>
> typedef struct VhostOps {
> VhostBackendType backend_type;
> @@ -214,6 +219,7 @@ typedef struct VhostOps {
> vhost_supports_device_state_op vhost_supports_device_state;
> vhost_set_device_state_fd_op vhost_set_device_state_fd;
> vhost_check_device_state_op vhost_check_device_state;
> + vhost_get_shmem_config_op vhost_get_shmem_config;
> } VhostOps;
>
> int vhost_backend_update_device_iotlb(struct vhost_dev *dev,
> diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
> index d7c09ffd34..e1b587a908 100644
> --- a/include/hw/virtio/vhost-user.h
> +++ b/include/hw/virtio/vhost-user.h
> @@ -32,6 +32,7 @@ enum VhostUserProtocolFeature {
> /* Feature 17 reserved for VHOST_USER_PROTOCOL_F_XEN_MMAP. */
> VHOST_USER_PROTOCOL_F_SHARED_OBJECT = 18,
> VHOST_USER_PROTOCOL_F_DEVICE_STATE = 19,
> + VHOST_USER_PROTOCOL_F_SHMEM = 20,
> VHOST_USER_PROTOCOL_F_MAX
> };
>
> --
> 2.45.2
>
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