Re: [Qemu-devel] [PATCH V5] spapr: Fix stale HTAB during live migration

[Sam Mendoza-Jonas <sam.mj@au1.ibm.com>]

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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