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Re: [Qemu-devel] [PATCH V5] spapr: Fix stale HTAB during live migration
From: |
Sam Mendoza-Jonas |
Subject: |
Re: [Qemu-devel] [PATCH V5] spapr: Fix stale HTAB during live migration |
Date: |
Tue, 26 Aug 2014 13:40:31 +1000 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 |
On 26/08/14 13:01, David Gibson wrote:
> On Fri, Aug 22, 2014 at 10:24:10AM +1000, Samuel Mendoza-Jonas wrote:
>> If a guest reboots during a running migration, changes to the
>> hash page table are not necessarily updated on the destination.
>> Opening a new file descriptor to the HTAB forces the migration
>> handler to resend the entire table.
>
> Of course, arguably this is a kernel bug - the htab fd should probably
> start re-reporting things if the htab reset ioctl() is called. But I
> guess we need a workaround for existing kernels anyway.
That's right, but as you say it would be nice to cover existing kernels.
>
> However, don't we still have the bug for TCG mode? spapr_reset_htab()
> just memset()s the whole hashtable in that case, which will actually
> clear all the dirty bits, whereas we need to set them.
>
True! I'll add a case for this, it should just be a matter of
checking & setting htab_first_pass.
--
Regards,
Sam Mendoza-Jonas
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