linux-kernel - Re: [PATCH 2/3] kvm: x86/mmu: Ensure TDP MMU roots are freed after yield

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Message-ID: <4471c5e6-16a1-65c4-aa59-185091a2ebbc@oracle.com>
Date:   Wed, 6 Jan 2021 18:37:24 +0100
From:   "Maciej S. Szmigiero" <maciej.szmigiero@...cle.com>
To:     Ben Gardon <bgardon@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Peter Shier <pshier@...gle.com>,
        Leo Hou <leohou1402@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [PATCH 2/3] kvm: x86/mmu: Ensure TDP MMU roots are freed after
 yield

On 06.01.2021 18:28, Ben Gardon wrote:
> On Wed, Jan 6, 2021 at 1:26 AM Maciej S. Szmigiero
> <maciej.szmigiero@...cle.com> wrote:
>>
>> Thanks for looking at it Ben.
>>
>> On 06.01.2021 00:38, Ben Gardon wrote:
>> (..)
>>>
>>> +Sean Christopherson, for whom I used a stale email address.
>>> .
>>> I tested this series by running kvm-unit-tests on an Intel Skylake
>>> machine. It did not introduce any new failures. I also ran the
>>> set_memory_region_test
>>
>> It's "memslot_move_test" that is crashing the kernel - a memslot
>> move test based on "set_memory_region_test".
> 
> I apologize if I'm being very dense, but I can't find this test
> anywhere.

No problem, the reproducer is available here:
https://gist.github.com/maciejsszmigiero/890218151c242d99f63ea0825334c6c0
as I stated in my original report.

> Is this something you have in-house but haven't upstreamed
> or just the test_move_memory_region(); testcase from
> set_memory_region_test? I have a similar memslot-moving-stress-test in
> the pipeline I need to send out, but I didn't think such a test
> existed yet and my test hadn't caught this issue.

The reproducer at that GitHub link is taken from my KVM memslot
test mini-set, itself based on set_memory_region_test.c from
KVM selftests.
The full mini-set will be posted as soon as I finish it :)

Thanks,
Maciej