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>
---
 hw/virtio/trace-events |  1 +
 hw/virtio/vhost.c      | 34 ++++++++++++++++++++++++++++++----
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
index 0e63c8739d..742ff0f90b 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
 vhost_section(const char *name, int r) "%s:%d"
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 57d15acd2b..4394ac0275 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -643,21 +643,47 @@ 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;
 
     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 = 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;
+    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;
     }
 
-- 
2.14.3

On Mon, 18 Dec 2017 20:13:38 +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>
> ---
>  hw/virtio/trace-events |  1 +
>  hw/virtio/vhost.c      | 34 ++++++++++++++++++++++++++++++----
>  2 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 0e63c8739d..742ff0f90b 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
>  vhost_section(const char *name, int r) "%s:%d"
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 57d15acd2b..4394ac0275 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -643,21 +643,47 @@ 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;
>  
>      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 = 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;
> +    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;
> +    }
is there a reason to keep dev->mem around after vhost_commit executed?
I'd suggest to use temporary local variable and free it on exit from function.

> +    if (!dev->started) {
also why memmap is generated this early and not right before first use?
here we might generate memap but not actually use it.

>          goto out;
>      }
>  

On Wed, 27 Dec 2017 14:19:03 +0100
Igor Mammedov <imammedo@redhat.com> wrote:

> On Mon, 18 Dec 2017 20:13:38 +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>
> > ---
[...]
> 
> > +    if (!dev->started) {
> also why memmap is generated this early and not right before first use?
> here we might generate memap but not actually use it.
I retract question, as commit + follow up set_mem_table could happen before
device is started. Having a comment here explaining it would be nice as
the call flow is obvious.


> >          goto out;
> >      }
> >  
> 
> 

* Igor Mammedov (imammedo@redhat.com) wrote:
> On Wed, 27 Dec 2017 14:19:03 +0100
> Igor Mammedov <imammedo@redhat.com> wrote:
> 
> > On Mon, 18 Dec 2017 20:13:38 +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>
> > > ---
> [...]
> > 
> > > +    if (!dev->started) {
> > also why memmap is generated this early and not right before first use?
> > here we might generate memap but not actually use it.
> I retract question, as commit + follow up set_mem_table could happen before
> device is started. Having a comment here explaining it would be nice as
> the call flow is obvious.

Yes, and I think I've seen that.  I'll add a comment.

Dave

> 
> > >          goto out;
> > >      }
> > >  
> > 
> > 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK