On Fri, 13 Mar 2020 at 12:31, Dr. David Alan Gilbert (git)
<dgilb...@redhat.com> wrote:
>
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
>
> Commit 355477f8c73e9 skips rom reset when we're an incoming migration
> so as not to overwrite shared ram in the ignore-shared migration
> optimisation.
> However, it's got an unexpected side effect that because it skips
> freeing the ROM data, when rom_reset gets called later on, after
> migration (e.g. during a reboot), the ROM does get reset to the original
> file contents. Because of seabios/x86's weird reboot process
> this confuses a reboot into hanging after a migration.
>
> Fixes: 355477f8c73e9 ("migration: do not rom_reset() during incoming
> migration")
> https://bugzilla.redhat.com/show_bug.cgi?id=1809380
>
> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> hw/core/loader.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
> QTAILQ_FOREACH(rom, &roms, next) {
> if (rom->fw_file) {
> continue;
> }
> + /*
> + * 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) && rom->data) {
> + /*
> + * Free it so that a rom_reset after migration doesn't overwrite
> a
> + * potentially modified 'rom'.
> + */
> + rom_free_data(rom);
Shouldn't this condition match the condition in rom_reset()
for when we call rom_free_data()? You want the behaviour
on a subsequent reset to match the behaviour you'd get
if you did a reset on the source end without the migration.
> + }
> +
> if (rom->data == NULL) {
> continue;
> }
If you put this check above your new one you wouldn't
need to check rom->data in it. Also it would make the
loop structure better match rom_reset(), which checks
rom->fw_file first, then rom->data, then has the
condition for "do we need to call rom_free_data()".
thanks
-- PMM
