linux-kernel - Re: [FYI PATCH] Revert "KVM: x86/mmu: Zap only TDP MMU leafs in kvm_zap_gfn

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Message-ID: <87tubmnwpu.fsf@redhat.com>
Date:   Fri, 25 Mar 2022 11:38:21 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [FYI PATCH] Revert "KVM: x86/mmu: Zap only TDP MMU leafs in
 kvm_zap_gfn_range()"

Sean Christopherson <seanjc@...gle.com> writes:

> On Mon, Mar 21, 2022, Paolo Bonzini wrote:
>> On 3/18/22 17:48, Paolo Bonzini wrote:
>> > This reverts commit cf3e26427c08ad9015956293ab389004ac6a338e.
>> > 
>> > Multi-vCPU Hyper-V guests started crashing randomly on boot with the
>> > latest kvm/queue and the problem can be bisected the problem to this
>> > particular patch.

...

>
> Vitaly, can you provide repro instructions?  A nearly-complete QEMU command line
> would be wonderful :-)  

The issue was observed with genuine Hyper-V guests, with or without any
Hyper-V enlightenments (not with Linux using Hyper-V enlightenments)
The QEMU command line is nothing special, e.g.

~/qemu/build/qemu-system-x86_64 -machine
q35,accel=kvm,kernel-irqchip=split -name guest=win2019 -cpu host -smp 16
-m 16384 -drive
file=/home/VMs/ws2019_gen1.qcow2,format=qcow2,if=none,id=drive-ide0-0-0
-device
ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1
-vnc :0 -rtc base=localtime,driftfix=slew --no-hpet -monitor stdio
--no-reboot

I'm also pretty sure I saw this on both AMD and Intel hosts, I can try
reproducing if needed.

-- 
Vitaly