On Thu, 14 Dec 2017 15:20:10 +0000
"Dr. David Alan Gilbert" <dgilb...@redhat.com> wrote:
> * Igor Mammedov (imamm...@redhat.com) wrote:
> > On Wed, 13 Dec 2017 18:08:02 +0000
> > "Dr. David Alan Gilbert (git)" <dgilb...@redhat.com> wrote:
> >
> > > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
> > >
> > > Move the log_dirty check into vhost_section.
> > >
> > > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> > > ---
> > > hw/virtio/trace-events | 3 +++
> > > hw/virtio/vhost.c | 20 +++++++++++++-------
> > > 2 files changed, 16 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> > > index 775461ae98..4a493bcd46 100644
> > > --- a/hw/virtio/trace-events
> > > +++ b/hw/virtio/trace-events
> > > @@ -1,5 +1,8 @@
> > > # See docs/devel/tracing.txt for syntax documentation.
> > >
> > > +# hw/virtio/vhost.c
> > > +vhost_section(const char *name, int r) "%s:%d"
> > > +
> > > # 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"
> > > virtqueue_fill(void *vq, const void *elem, unsigned int len, unsigned
> > > int idx) "vq %p elem %p len %u idx %u"
> > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > > index e4290ce93d..e923219e63 100644
> > > --- a/hw/virtio/vhost.c
> > > +++ b/hw/virtio/vhost.c
> > > @@ -27,6 +27,7 @@
> > > #include "hw/virtio/virtio-access.h"
> > > #include "migration/blocker.h"
> > > #include "sysemu/dma.h"
> > > +#include "trace.h"
> > >
> > > /* enabled until disconnected backend stabilizes */
> > > #define _VHOST_DEBUG 1
> > > @@ -567,18 +568,12 @@ static void vhost_set_memory(MemoryListener
> > > *listener,
> > > memory_listener);
> > > hwaddr start_addr = section->offset_within_address_space;
> > > ram_addr_t size = int128_get64(section->size);
> > > - bool log_dirty =
> > > - memory_region_get_dirty_log_mask(section->mr) & ~(1 <<
> > > DIRTY_MEMORY_MIGRATION);
> > > int s = offsetof(struct vhost_memory, regions) +
> > > (dev->mem->nregions + 1) * sizeof dev->mem->regions[0];
> > > void *ram;
> > >
> > > dev->mem = g_realloc(dev->mem, s);
> > >
> > > - if (log_dirty) {
> > > - add = false;
> > > - }
> > > -
> > > assert(size);
> > >
> > > /* Optimize no-change case. At least cirrus_vga does this a lot at
> > > this time. */
> > > @@ -611,8 +606,19 @@ static void vhost_set_memory(MemoryListener
> > > *listener,
> > >
> > > static bool vhost_section(MemoryRegionSection *section)
> > > {
> > > - return memory_region_is_ram(section->mr) &&
> > > + bool result;
> > > + bool log_dirty = memory_region_get_dirty_log_mask(section->mr) &
> > > + ~(1 << DIRTY_MEMORY_MIGRATION);
> > > + result = memory_region_is_ram(section->mr) &&
> > > !memory_region_is_rom(section->mr);
> > > +
> > > + /* Vhost doesn't handle any block which is doing dirty-tracking other
> > > + * than migration; this typically fires on VGA areas.
> > > + */
> > > + result &= !log_dirty;
> > before patch even if log_dirty, vhost_set_memory will still proceed
> > and may remove dirty section from memmap and set memory_changed = true
> >
> > but with this patch it will just ignore such section,
> > I'm not sure it's right (it might be right with new approach add/nop
> > but then this patch should go after new code in place and old one
> > if gone).
>
> I thought about that, but then I came to the conclusion that the whole
> idea is that we're supposed to be ignoring these regions - so why
> should they cause any change to the behaviour of vhost at all?
> Thus this way seems safer.
Could it happen that, while being deleted section could become dirty
at the same time? if that could happen then region_del won't process
section and won't call unref on it either.
one more reason to operate on tmp_mem_sections and then
unconditionally unref old mem_sections at commit time at
the right time (after set mem table).
>
> Dave
>
> > > +
> > > + trace_vhost_section(section->mr->name, result);
> > > + return result;
> > > }
> > >
> > > static void vhost_begin(MemoryListener *listener)
> >
> --
> Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
