Re: [Qemu-devel] [PATCH] vhost-user: modify SET_LOG_BASE to pass mmap size and offset

["Marc-André Lureau" <mlureau@redhat.com>]

Hi

----- Original Message -----
> Unlike the kernel, vhost-user application accesses log table by
> mmaping it to its user space. This change adds two new fields to
> VhostUserMsg payload: mmap_size, and mmap_offset and make QEMU to
> pass the to vhost-user application in VHOST_USER_SET_LOG_BASE
> request.
> 
> Signed-off-by: Victor Kaplansky <victork@redhat.com>

What's the motivation for doing this? The offset is always 0, and the size must at least match the size of VM memory.

> 
> ---
>  hw/virtio/vhost-user.c    | 11 +++++++++--
>  tests/vhost-user-test.c   |  8 ++++++++
>  docs/specs/vhost-user.txt |  8 +++++++-
>  3 files changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 83c84f1..46c63bc 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -75,6 +75,11 @@ typedef struct VhostUserMemory {
>      VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
>  } VhostUserMemory;
>  
> +typedef struct VhostUserLog {
> +    uint64_t mmap_size;
> +    uint64_t mmap_offset;
> +} VhostUserLog;
> +
>  typedef struct VhostUserMsg {
>      VhostUserRequest request;
>  
> @@ -89,6 +94,7 @@ typedef struct VhostUserMsg {
>          struct vhost_vring_state state;
>          struct vhost_vring_addr addr;
>          VhostUserMemory memory;
> +        VhostUserLog log;
>      } payload;
>  } QEMU_PACKED VhostUserMsg;
>  
> @@ -200,8 +206,9 @@ static int vhost_user_set_log_base(struct vhost_dev *dev,
> uint64_t base,
>      VhostUserMsg msg = {
>          .request = VHOST_USER_SET_LOG_BASE,
>          .flags = VHOST_USER_VERSION,
> -        .payload.u64 = base,
> -        .size = sizeof(msg.payload.u64),
> +        .payload.log.mmap_size = log->size,
> +        .payload.log.mmap_offset = 0,
> +        .size = sizeof(msg.payload.log),
>      };
>  
>      if (shmfd && log->fd != -1) {
> diff --git a/tests/vhost-user-test.c b/tests/vhost-user-test.c
> index b6dde75..f005ecf 100644
> --- a/tests/vhost-user-test.c
> +++ b/tests/vhost-user-test.c
> @@ -86,6 +86,11 @@ typedef struct VhostUserMemory {
>      VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
>  } VhostUserMemory;
>  
> +typedef struct VhostUserLog {
> +    uint64_t mmap_size;
> +    uint64_t mmap_offset;
> +} VhostUserLog;
> +
>  typedef struct VhostUserMsg {
>      VhostUserRequest request;
>  
> @@ -94,10 +99,13 @@ typedef struct VhostUserMsg {
>      uint32_t flags;
>      uint32_t size; /* the following payload size */
>      union {
> +#define VHOST_USER_VRING_IDX_MASK   (0xff)
> +#define VHOST_USER_VRING_NOFD_MASK  (0x1<<8)
>          uint64_t u64;
>          struct vhost_vring_state state;
>          struct vhost_vring_addr addr;
>          VhostUserMemory memory;
> +        VhostUserLog log;
>      } payload;
>  } QEMU_PACKED VhostUserMsg;
>  
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index e0d71e2..eb8f2b2 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -98,6 +98,7 @@ typedef struct VhostUserMsg {
>          struct vhost_vring_state state;
>          struct vhost_vring_addr addr;
>          VhostUserMemory memory;
> +        VhostUserLog log;
>      };
>  } QEMU_PACKED VhostUserMsg;
>  
> @@ -282,7 +283,12 @@ Message types
>        Master payload: u64
>        Slave payload: N/A
>  
> -      Sets the logging base address.
> +      Sets logging shared memory space.
> +      When slave has VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol
> +      feature, the log memory fd is provided in the ancillary data of
> +      VHOST_USER_SET_LOG_BASE message, the size and offset of shared
> +      memory area provided in the message.
> +
>  
>   * VHOST_USER_SET_LOG_FD
>  
> --
> --Victor
>