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

[Michael S. Tsirkin]

On Wed, Nov 11, 2015 at 09:32:17AM -0500, Marc-André Lureau wrote:
> 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 <address@hidden>
> 
> What's the motivation for doing this? The offset is always 0, and the size 
> must at least match the size of VM memory.

Remote doesn't know the size though, and offset is only there
in the current implementation.

> > 
> > ---
> >  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
> >