Re: [Qemu-devel] [PATCH 2/2] postcopy: Require RAMBlocks that are whole pages

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > It turns out that it's legal to create a VM with RAMBlocks that aren't
> > a multiple of the pagesize in use; e.g. a 1025M main memory using
> > 2M host pages.  That breaks postcopy's atomic placement of pages,
> > so disallow it.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 
> Reviewed-by: Juan Quintela <quintela@redhat.com>

Thanks

> >      }
> >  
> >      /* We don't support postcopy with shared RAM yet */
> > -    if (qemu_ram_foreach_block(test_range_shared, NULL)) {
> > +    if (qemu_ram_foreach_block(test_ramblock_postcopiable, NULL)) {
> 
> When I was looking at this code, I still don't know why
> qemu_ram_foreach_block() don't pass the block directly.  It needs it
> almost all callers.
> 
> When I saw it I was about to change it, but got sidetracked on other
> things :-p

I think originally it passed very little information at all, and
that RAMBlocks were these mystical things no one outside exec.c
was really supposed to know about.

Dave

> Later, Juan.
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK