Re: [Qemu-devel] [RFC 4/7] vhost: update_mem_cb implementation

[Igor Mammedov]

On Wed, 29 Nov 2017 18:50:23 +0000
"Dr. David Alan Gilbert (git)" <address@hidden> wrote:

> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> Add the meat of update_mem_cb;  this is called for each region,
> to add a region to our temporary list.
> Our temporary list is in order we look to see if this
> region can be merged with the current head of list.
> 
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  hw/virtio/trace-events |  2 ++
>  hw/virtio/vhost.c      | 55 
> +++++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 56 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 4a493bcd46..92fadec192 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -2,6 +2,8 @@
>  
>  # hw/virtio/vhost.c
>  vhost_section(const char *name, int r) "%s:%d"
> +vhost_update_mem_cb(const char *name, uint64_t gpa, uint64_t size, uint64_t 
> host) "%s: 0x%"PRIx64"+0x%"PRIx64" @ 0x%"PRIx64
> +vhost_update_mem_cb_abut(const char *name, uint64_t new_size) "%s: 0x%"PRIx64
>  
>  # hw/virtio/virtio.c
>  virtqueue_alloc_element(void *elem, size_t sz, unsigned in_num, unsigned 
> out_num) "elem %p size %zd in_num %u out_num %u"
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index c959a59fb3..7e3c6ae032 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -638,11 +638,64 @@ struct vhost_update_mem_tmp {
>  /* Called for each MRS from vhost_update_mem */
>  static int vhost_update_mem_cb(MemoryRegionSection *mrs, void *opaque)
>  {
> +    struct vhost_update_mem_tmp *vtmp = opaque;
> +    struct vhost_memory_region *cur_vmr;
> +    bool need_add = true;
> +    uint64_t mrs_size;
> +    uint64_t mrs_gpa;
> +    uintptr_t mrs_host;
> +
>      if (!vhost_section(mrs)) {
>          return 0;
>      }
> +    mrs_size = int128_get64(mrs->size);
> +    mrs_gpa  = mrs->offset_within_address_space;
> +    mrs_host = (uintptr_t)memory_region_get_ram_ptr(mrs->mr) +
> +                         mrs->offset_within_region;
> +
> +    trace_vhost_update_mem_cb(mrs->mr->name, mrs_gpa, mrs_size,
> +                              (uint64_t)mrs_host);
> +
> +    if (vtmp->nregions) {
What forces you to maintain helper vhost_memory_region array
instead of MemoryRegionSection array?

> +        /* Since we already have at least one region, lets see if
> +         * this extends it; since we're scanning in order, we only
> +         * have to look at the last one, and the FlatView that calls
> +         * us shouldn't have overlaps.
> +         */
> +        struct vhost_memory_region *prev_vmr = vtmp->regions +
> +                                               (vtmp->nregions - 1);
> +        uint64_t prev_gpa_start = prev_vmr->guest_phys_addr;
> +        uint64_t prev_gpa_end   = range_get_last(prev_gpa_start,
> +                                                 prev_vmr->memory_size);
> +        uint64_t prev_host_start = prev_vmr->userspace_addr;
> +        uint64_t prev_host_end   = range_get_last(prev_host_start,
> +                                                  prev_vmr->memory_size);
> +
> +        if (prev_gpa_end + 1 == mrs_gpa &&
> +            prev_host_end + 1 == mrs_host &&
> +            (!vtmp->dev->vhost_ops->vhost_backend_can_merge ||
> +                vtmp->dev->vhost_ops->vhost_backend_can_merge(vtmp->dev,
> +                    mrs_host, mrs_size,
> +                    prev_host_start, prev_vmr->memory_size))) {
> +            /* The two regions abut */
> +            need_add = false;
> +            mrs_size = mrs_size + prev_vmr->memory_size;
> +            prev_vmr->memory_size = mrs_size;
> +            trace_vhost_update_mem_cb_abut(mrs->mr->name, mrs_size);
> +        }
> +    }
> +
> +    if (need_add) {
> +        vtmp->nregions++;
> +        vtmp->regions = g_realloc_n(vtmp->regions, vtmp->nregions,
> +                                    sizeof(vtmp->regions[0]));
> +        cur_vmr = &vtmp->regions[vtmp->nregions - 1];
> +        cur_vmr->guest_phys_addr = mrs_gpa;
> +        cur_vmr->memory_size     = mrs_size;
> +        cur_vmr->userspace_addr  = mrs_host;
> +        cur_vmr->flags_padding = 0;
> +    }
>  
> -    /* TODO */
>      return 0;
>  }
>