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Subject: Re: [syzbot] WARNING in kvm_mmu_uninit_tdp_mmu (2)
From:   Maxim Levitsky <mlevitsk@redhat.com>
To:     Sean Christopherson <seanjc@google.com>
Cc:     syzbot <syzbot+a8ad3ee1525a0c4b40ec@syzkaller.appspotmail.com>,
        bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
        jmattson@google.com, joro@8bytes.org, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, mingo@redhat.com,
        pbonzini@redhat.com, syzkaller-bugs@googlegroups.com,
        tglx@linutronix.de, vkuznets@redhat.com, wanpengli@tencent.com,
        x86@kernel.org
Date:   Thu, 28 Apr 2022 20:21:56 +0300
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On Thu, 2022-04-28 at 20:16 +0300, Maxim Levitsky wrote:
> On Thu, 2022-04-28 at 15:32 +0000, 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.
> > 
> 
> This is the patch series (mostly attempt to turn svm to mini library,
> but I don't know if this is worth it.
> It was done so that ipi_stress could use  nesting itself to wait for IPI
> from within a nested guest. I usually don't use it.
> 
> This is more or less how I was running it lately (I have a wrapper script)
> 
> 
> ./x86/run x86/ipi_stress.flat \
>         -global kvm-pit.lost_tick_policy=discard \
> 	        -machine kernel-irqchip=on -name debug-threads=on  \
> 	        \
> 	        -smp 8 \
> 	        -cpu host,x2apic=off,svm=off,-hypervisor \
> 	        -overcommit cpu-pm=on \
> 	        -m 4g -append "0 10000"

I forgot to mention: this should be run in a loop.

Best regards,
	Maxim Levitsky

> 
> 
> Its not fully finised for upstream, I will get to it soon.
> 
> 'cpu-pm=on' won't work for you as this fails due to non atomic memslot
> update bug for which I have a small hack in qemu, and it is on my
> backlog to fix it correctly.
> 
> Mostly likely cpu_pm=off will also reproduce it.
> 
> 
> Test was run in a guest, natively this doesn't seem to reproduce.
> tdp mmu was used for both L0 and L1.
> 
> Best regards,
> 	Maxim levitsky