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

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Date:   Thu, 28 Apr 2022 20:16:47 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     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,
        pbonzini@...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 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"


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

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