Re: [Qemu-devel] [PATCH v7 4/7] vhost: Regenerate region list from changed sections list

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 19 Jan 2018 10:39:21 +0000
"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:

> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Compare the sections list that's just been generated, and if it's
> different from the old one regenerate the region list.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>

> ---
>  hw/virtio/trace-events |  1 +
>  hw/virtio/vhost.c      | 39 +++++++++++++++++++++++++++++++++++----
>  2 files changed, 36 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index ab9da06244..606e4fc949 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -1,6 +1,7 @@
>  # See docs/devel/tracing.txt for syntax documentation.
>  
>  # hw/virtio/vhost.c
> +vhost_commit(bool started, bool changed) "Started: %d Changed: %d"
>  vhost_region_add_section(const char *name, uint64_t gpa, uint64_t size, uint64_t host) "%s: 0x%"PRIx64"+0x%"PRIx64" @ 0x%"PRIx64
>  vhost_region_add_section_abut(const char *name, uint64_t new_size) "%s: 0x%"PRIx64
>  
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 15d466356e..0485acdfc8 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -637,21 +637,52 @@ static void vhost_commit(MemoryListener *listener)
>      MemoryRegionSection *old_sections;
>      int n_old_sections;
>      uint64_t log_size;
> +    size_t regions_size;
>      int r;
>      int i;
> +    bool changed = false;
>  
> +    /* Note we can be called before the device is started, but then
> +     * starting the device calls set_mem_table, so we need to have
> +     * built the data structures.
> +     */
>      old_sections = dev->mem_sections;
>      n_old_sections = dev->n_mem_sections;
>      dev->mem_sections = dev->tmp_sections;
>      dev->n_mem_sections = dev->n_tmp_sections;
>  
> -    if (!dev->memory_changed) {
> -        goto out;
> +    if (dev->n_mem_sections != n_old_sections) {
> +        changed = true;
> +    } else {
> +        /* Same size, lets check the contents */
> +        changed = n_old_sections && memcmp(dev->mem_sections, old_sections,
> +                         n_old_sections * sizeof(old_sections[0])) != 0;
>      }
> -    if (!dev->started) {
> +
> +    trace_vhost_commit(dev->started, changed);
> +    if (!changed) {
>          goto out;
>      }
> -    if (dev->mem_changed_start_addr > dev->mem_changed_end_addr) {
> +
> +    /* Rebuild the regions list from the new sections list */
> +    regions_size = offsetof(struct vhost_memory, regions) +
> +                       dev->n_mem_sections * sizeof dev->mem->regions[0];
> +    dev->mem = g_realloc(dev->mem, regions_size);
> +    dev->mem->nregions = dev->n_mem_sections;
> +    used_memslots = dev->mem->nregions;
> +    for (i = 0; i < dev->n_mem_sections; i++) {
> +        struct vhost_memory_region *cur_vmr = dev->mem->regions + i;
> +        struct MemoryRegionSection *mrs = dev->mem_sections + i;
> +
> +        cur_vmr->guest_phys_addr = mrs->offset_within_address_space;
> +        cur_vmr->memory_size     = int128_get64(mrs->size);
> +        cur_vmr->userspace_addr  =
> +            (uintptr_t)memory_region_get_ram_ptr(mrs->mr) +
> +            mrs->offset_within_region;
> +        cur_vmr->flags_padding   = 0;
> +    }
> +
> +    if (!dev->started) {
>          goto out;
>      }
>