Re: [Qemu-devel] [PULL 5/8] target-sparc: Use global registers for the register window - Mark Cave-Ayland

From: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
To: Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PULL 5/8] target-sparc: Use global registers for the register window
Date: Fri, 24 Jun 2016 11:42:21 +0100	[thread overview]
Message-ID: <6c98d3be-ec72-cd33-1e74-fc32dea6a865@ilande.co.uk> (raw)
In-Reply-To: <03d5a05a-2674-b755-49d7-5a46dcadc237@redhat.com>

On 24/06/16 07:36, Paolo Bonzini wrote:

> On 24/06/2016 05:57, Richard Henderson wrote:
>>
>> Whatever happens, it happens after 10GB of logs, which is simply too
>> much to sift through.  I've tried to narrow it down, but the lack of a
>> hardware tlb refill means that we get hundreds of thousands of Data
>> Access Faults that are simply TLB misses and not the actual Segmentation
>> Fault in question.
>>
>> It doesn't seem to affect other OSes, so I can't imagine what quirk is
>> being exercised in this case.
>>
>> As loath as I am to suggest it, we may have to revert the sparc indirect
>> register patch for the release.
>
> We have more than a month.  If it's reproducible, it can be fixed. :)
>
>> I do now ping the rest of my sparc improvements patchset.  It's
>> completely independent of the use of indirect registers.
>
> Mark, perhaps you can try to use migration to reduce the amount of
> logging?  (Start QEMU with -snapshot, try to stop the vm before it
> fails.  If you succeed, do a "migrate exec:cat>foo.sav" followed by
> "commit"; if you fail, try again).

Yeah, given the improvements that Richard has made, I'd prefer not to 
revert if at all possible. Finally I have some spare time today so I'll 
try and get this down to an easily-testable qcow2 image that can 
reproduce the issue.

ATB,

Mark.