Re: [Qemu-devel] [PATCH v4] migration: do not rom_reset() during incoming migration

[Catherine Ho]

Sorry for the noise, is there any more comment for this patch?
Without this patch, ignore shared capabilities can not be used on arm64

B.R.
Catherine

On Tue, 16 Apr 2019 at 10:51, Peter Xu <address@hidden> wrote:

> On Mon, Apr 08, 2019 at 04:42:13AM -0400, Catherine Ho 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 <address@hidden>
> > Suggested-by: Peter Xu <address@hidden>
> > Signed-off-by: Catherine Ho <address@hidden>
>
> Acked-by: Peter Xu <address@hidden>
>
> --
> Peter Xu
>