Re: [Qemu-devel] [PATCH v5 4/7] vhost: Merge sections added to temporary list

[Igor Mammedov]

On Mon, 18 Dec 2017 20:13:37 +0000
"Dr. David Alan Gilbert (git)" <address@hidden> wrote:

> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> As sections are reported by the listener to the _nop and _add
> methods, add them to the temporary section list but now merge them
> with the previous section if the new one abuts and the backend allows.
> 
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
beside small nit patch looks good to me, so with it fixed

Reviewed-by: Igor Mammedov <address@hidden>

> ---
>  hw/virtio/trace-events |  2 ++
>  hw/virtio/vhost.c      | 70 
> +++++++++++++++++++++++++++++++++++++++++++-------
>  2 files changed, 63 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 4a493bcd46..0e63c8739d 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -1,6 +1,8 @@
>  # See docs/devel/tracing.txt for syntax documentation.
>  
>  # hw/virtio/vhost.c
> +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
>  vhost_section(const char *name, int r) "%s:%d"
>  
>  # hw/virtio/virtio.c
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 18611f0d40..57d15acd2b 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -709,14 +709,65 @@ out:
>      return;
>  }
>  
> -static void vhost_add_section(struct vhost_dev *dev,
> -                              MemoryRegionSection *section)
> +/* Adds the section data to the tmp_section structure.
> + * It relies on the listener calling us in memory address order
> + * and for each region (via the _add and _nop methods) to
> + * join neighbours.
> + */
> +static void vhost_region_add_section(struct vhost_dev *dev,
> +                                 MemoryRegionSection *section)
wrong alignment, should be on '('

>  {
> -    ++dev->n_tmp_sections;
> -    dev->tmp_sections = g_renew(MemoryRegionSection, dev->tmp_sections,
> -                                dev->n_tmp_sections);
> -    dev->tmp_sections[dev->n_tmp_sections - 1] = *section;
> -    memory_region_ref(section->mr);
> +    bool need_add = true;
> +    uint64_t mrs_size = int128_get64(section->size);
> +    uint64_t mrs_gpa = section->offset_within_address_space;
> +    uintptr_t mrs_host = (uintptr_t)memory_region_get_ram_ptr(section->mr) +
> +                         section->offset_within_region;
> +
> +    trace_vhost_region_add_section(section->mr->name, mrs_gpa, mrs_size,
> +                                   mrs_host);
> +
> +    if (dev->n_tmp_sections) {
> +        /* Since we already have at least one section, 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.
> +         */
> +        MemoryRegionSection *prev_sec = dev->tmp_sections +
> +                                               (dev->n_tmp_sections - 1);
> +        uint64_t prev_gpa_start = prev_sec->offset_within_address_space;
> +        uint64_t prev_size = int128_get64(prev_sec->size);
> +        uint64_t prev_gpa_end   = range_get_last(prev_gpa_start, prev_size);
> +        uint64_t prev_host_start =
> +                        (uintptr_t)memory_region_get_ram_ptr(prev_sec->mr) +
> +                        prev_sec->offset_within_region;
> +        uint64_t prev_host_end   = range_get_last(prev_host_start, 
> prev_size);
> +
> +        if (prev_gpa_end + 1 == mrs_gpa &&
> +            prev_host_end + 1 == mrs_host &&
> +            section->mr == prev_sec->mr &&
> +            (!dev->vhost_ops->vhost_backend_can_merge ||
> +                dev->vhost_ops->vhost_backend_can_merge(dev,
> +                    mrs_host, mrs_size,
> +                    prev_host_start, prev_size))) {
> +            /* The two sections abut */
> +            need_add = false;
> +            prev_sec->size = int128_add(prev_sec->size, section->size);
> +            trace_vhost_region_add_section_abut(section->mr->name,
> +                                                mrs_size + prev_size);
> +        }
> +    }
> +
> +    if (need_add) {
> +        ++dev->n_tmp_sections;
> +        dev->tmp_sections = g_renew(MemoryRegionSection, dev->tmp_sections,
> +                                    dev->n_tmp_sections);
> +        dev->tmp_sections[dev->n_tmp_sections - 1] = *section;
> +        /* The flatview isn't stable and we don't use it, making it NULL
> +         * means we can memcmp the list.
> +         */
> +        dev->tmp_sections[dev->n_tmp_sections - 1].fv = NULL;
> +        memory_region_ref(section->mr);
> +    }
>  }
>  
>  static void vhost_region_add(MemoryListener *listener,
> @@ -728,11 +779,12 @@ static void vhost_region_add(MemoryListener *listener,
>      if (!vhost_section(section)) {
>          return;
>      }
> +    vhost_region_add_section(dev, section);
>  
> -    vhost_add_section(dev, section);
>      vhost_set_memory(listener, section, true);
>  }
>  
> +/* Called on regions that have not changed */
>  static void vhost_region_nop(MemoryListener *listener,
>                               MemoryRegionSection *section)
>  {
> @@ -743,7 +795,7 @@ static void vhost_region_nop(MemoryListener *listener,
>          return;
>      }
>  
> -    vhost_add_section(dev, section);
> +    vhost_region_add_section(dev, section);
>  }
>  
>  static void vhost_region_del(MemoryListener *listener,