From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Juan Quintela <quintela@redhat.com>,
qemu-devel@nongnu.org, Peter Xu <peterx@redhat.com>,
Markus Armbruster <armbru@redhat.com>,
Catherine Ho <catherine.hecx@gmail.com>,
Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH v4] migration: do not rom_reset() during incoming migration
Date: Wed, 5 Jun 2019 19:31:22 +0100 [thread overview]
Message-ID: <20190605183122.GJ2669@work-vm> (raw)
In-Reply-To: <1554712933-18682-1-git-send-email-catherine.hecx@gmail.com>
Paolo, can you take this one please.
* Catherine Ho (catherine.hecx@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-kotov@yandex-team.ru>
> Suggested-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: Catherine Ho <catherine.hecx@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 / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2019-06-05 18:38 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-08 1:56 [Qemu-devel] [PATCH v3] migration: do not rom_reset() during incoming migration Catherine Ho
2019-04-08 1:56 ` Catherine Ho
2019-04-08 3:31 ` Peter Xu
2019-04-08 3:31 ` Peter Xu
2019-04-08 8:42 ` [Qemu-devel] [PATCH v4] " Catherine Ho
2019-04-08 8:42 ` Catherine Ho
2019-04-16 1:46 ` Catherine Ho
2019-04-16 1:46 ` Catherine Ho
2019-04-16 2:51 ` Peter Xu
2019-04-16 2:51 ` Peter Xu
2019-05-13 3:00 ` Catherine Ho
2019-06-05 18:31 ` Dr. David Alan Gilbert [this message]
2019-08-14 10:40 ` Catherine Ho
2019-08-14 12:34 ` Paolo Bonzini
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