* Halil Pasic (pa...@linux.vnet.ibm.com) wrote:
>
>
> On 03/09/2017 02:22 PM, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
> >
> > Postcopy doesn't support migration of RAM shared with another process
> > yet (we've got a bunch of things to understand).
> > Check for the case and don't allow postcopy to be enabled.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> > ---
> > migration/postcopy-ram.c | 18 ++++++++++++++++++
> > 1 file changed, 18 insertions(+)
> >
> > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> > index effbeb6..dc80dbb 100644
> > --- a/migration/postcopy-ram.c
> > +++ b/migration/postcopy-ram.c
> > @@ -95,6 +95,19 @@ static bool ufd_version_check(int ufd)
> > return true;
> > }
> >
> > +/* Callback from postcopy_ram_supported_by_host block iterator.
> > + */
> > +static int test_range_shared(const char *block_name, void *host_addr,
> > + ram_addr_t offset, ram_addr_t length, void
> > *opaque)
> > +{
> > + if (qemu_ram_is_shared(qemu_ram_block_by_name(block_name))) {
> > + error_report("Postcopy on shared RAM (%s) is not yet supported",
> > + block_name);
> > + return 1;
> > + }
> > + return 0;
> > +}
> > +
>
> Hm, this stuff with the iterator seemed a bit strange (too complicated)
> first, but I'm not familiar with this code. I have no idea why is
> RAMBlockIterFunc
>
> typedef int (RAMBlockIterFunc)(const char *block_name, void *host_addr,
> ram_addr_t offset, ram_addr_t length, void *opaque)
>
> and not
>
> typedef int (RAMBlockIterFunc)(RAMBlock *block, void *opaque).
>
> The reason does not seem to be abstraction.
It is, it's because the contents of RAMBlock are private.
> > /*
> > * Note: This has the side effect of munlock'ing all of RAM, that's
> > * normally fine since if the postcopy succeeds it gets turned back on at
> > the
> > @@ -127,6 +140,11 @@ bool postcopy_ram_supported_by_host(void)
> > goto out;
> > }
> >
> > + /* We don't support postcopy with shared RAM yet */
> > + if (qemu_ram_foreach_block(test_range_shared, NULL)) {
> > + goto out;
> > + }
> > +
>
> But using ram_list directly does not seem to be a good alternative to me,
> and I do not see a third alternative.
>
> So besides some cosmetic stuff I have nothing to add. Cosmetic stuff is:
> * why range instead of block in test_range_shared
> * I think we could move this up so that we can return directly
> and do not acquire resources which need cleanup
>
> Regardless of the cosmetics:
> Reviewed-by: Halil Pasic <pa...@linux.vnet.ibm.com>
Dave
>
> > /*
> > * userfault and mlock don't go together; we'll put it back later if
> > * it was enabled.
> >
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
