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Re: [Xen-devel] [RFC Patch v3 18/18] x86/hvm: Always set pending event injection when loading VMC[BS] state.

On 9/17/14 2:56 AM, Wen Congyang wrote:
On 09/11/2014 06:35 PM, Tim Deegan wrote:
At 10:06 -0500 on 10 Sep (1410340016), Aravind Gopalakrishnan wrote:
You mention that this 'fix' is just copied for svm. But you have not
seen the problem of "VM_ENTRY_INTR_INFO may be valid" (whose svm
equivalent is "vmcb->eventinj.bytes is valid").
My concern is that we should test colo mode for svm first, since, if the
problem is never really seen on svm, then fix may not be _necessary_
I think it's obvious by inspection of the code (and indeed the patch)
that SVM has the equivalent bug.

At this point, my problems are with test setups. I can help testing
scenarios, but as Wen had mentioned, 'colo testing' might be the way to
So, if I can get some pointers to how I can reproduce the issue at hand,
then it would be very helpful.

(Tim had mentioned we could try to simulate it by running a guest that
takes lot of faults and save-restore another guest over it. However,
I am not having much luck following this route. I got a hvm guest to
continuously take SW exceptions on all vcpus and tried to save-restore.
I can't see vmcb->eventinj.bytes containing any valid info.)
Although I think that getting COLO running on SVM is a gret idea, it
shouldn't block acceptance of this fix.  I've attached a program
that tests for the bug.  Run it against any HVM guest (and then
destroy the guest because the test will have corrupted its state).
Hi, Aravind Gopalakrishnan

Do you have time to test this patch with the test program?

Thanks for the test program Tim.
I tested it on a HVM guest and test prints 'good' w/ the patch applied and 'bad' w/o the patch.


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