Hi Paolo
Ping, is any other comment I hadn't addressed?
Cheers
Catherine
On Thu, 6 Jun 2019 at 02:31, Dr. David Alan Gilbert <dgilb...@redhat.com>
wrote:
> Paolo, can you take this one please.
>
> * Catherine Ho (catherine.h...@gmail.com) wrote:
> > Commit 18269069c310 ("migration: Introduce ignore-shared capability")
> > addes ignore-shared capability to bypass the shared ramblock (e,g,
> > membackend + numa node). It does good to live migration.
> >
> > As told by Yury,this commit expectes that QEMU doesn't write to guest RAM
> > until VM starts, but it does on aarch64 qemu:
> > Backtrace:
> > 1 0x000055f4a296dd84 in address_space_write_rom_internal () at
> > exec.c:3458
> > 2 0x000055f4a296de3a in address_space_write_rom () at exec.c:3479
> > 3 0x000055f4a2d519ff in rom_reset () at hw/core/loader.c:1101
> > 4 0x000055f4a2d475ec in qemu_devices_reset () at hw/core/reset.c:69
> > 5 0x000055f4a2c90a28 in qemu_system_reset () at vl.c:1675
> > 6 0x000055f4a2c9851d in main () at vl.c:4552
> >
> > Actually, on arm64 virt marchine, ramblock "dtb" will be filled into ram
> > druing rom_reset. In ignore-shared incoming case, this rom filling
> > is not required since all the data has been stored in memory backend
> > file.
> >
> > Further more, as suggested by Peter Xu, if we do rom_reset() now with
> > these ROMs then the RAM data should be re-filled again too with the
> > migration stream coming in.
> >
> > Fixes: commit 18269069c310 ("migration: Introduce ignore-shared
> > capability")
> > Suggested-by: Yury Kotov <yury-ko...@yandex-team.ru>
> > Suggested-by: Peter Xu <pet...@redhat.com>
> > Signed-off-by: Catherine Ho <catherine.h...@gmail.com>
> > ---
> > hw/core/loader.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/hw/core/loader.c b/hw/core/loader.c
> > index fe5cb24122..040109464b 100644
> > --- a/hw/core/loader.c
> > +++ b/hw/core/loader.c
> > @@ -1087,6 +1087,15 @@ static void rom_reset(void *unused)
> > {
> > Rom *rom;
> >
> > + /*
> > + * We don't need to fill in the RAM with ROM data because we'll fill
> > + * the data in during the next incoming migration in all cases.
> Note
> > + * that some of those RAMs can actually be modified by the guest on
> ARM
> > + * so this is probably the only right thing to do here.
> > + */
> > + if (runstate_check(RUN_STATE_INMIGRATE))
> > + return;
> > +
> > QTAILQ_FOREACH(rom, &roms, next) {
> > if (rom->fw_file) {
> > continue;
> > --
> > 2.17.1
> >
> --
> Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
>
