linux-kernel - Re: [syzbot] WARNING in kvm_mmu_uninit_tdp

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Message-ID: <47eb853424ef6c7dd6439ac33dfeb64a29f49c44.camel@redhat.com>
Date:   Thu, 28 Apr 2022 20:26:49 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     syzbot <syzbot+a8ad3ee1525a0c4b40ec@...kaller.appspotmail.com>,
        bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
        jmattson@...gle.com, joro@...tes.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        vkuznets@...hat.com, wanpengli@...cent.com, x86@...nel.org
Subject: Re: [syzbot] WARNING in kvm_mmu_uninit_tdp_mmu (2)

On Thu, 2022-04-28 at 19:22 +0200, Paolo Bonzini wrote:
> On 4/28/22 17:32, Sean Christopherson wrote:
> > On Tue, Apr 26, 2022, Maxim Levitsky wrote:
> > > I can reproduce this in a VM, by running and CTRL+C'in my ipi_stress test,
> > 
> > Can you post your ipi_stress test?  I'm curious to see if I can repro, and also
> > very curious as to what might be unique about your test.  I haven't been able to
> > repro the syzbot test, nor have I been able to repro by killing VMs/tests.
> 
> Did you test with CONFIG_PREEMPT=y?

yes, I test with CONFIG_PREEMPT but I only enabled it a day ago,
I think I had seen this warning before, but could bit, I'll check
if that fails without CONFIG_PREEMPT as well.


What I recently changed, is that I enabled lockdep and related settings
on all my machines and VMs, I enabled CONFIG_PREEMPT, and I also
switched to tdp_mmu on all systems.

Bugs are biting but it is better this way, especially to weed out
the last bugs of my nested avic code :)

Best regards,
	Maxim Levitsky


> 
> (BTW, the fact that it reproduces under 5.17 is a mixed blessing, 
> because it means that we can analyze/stare at a simpler codebase).
> 
> Paolo
>