linux-kernel - Re: [PATCH 0/2] KVM: x86: Fix dangling page reference in TDP MMU

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Date:   Mon, 13 Dec 2021 20:18:19 +0000
From:   Ignat Korchagin <ignat@...udflare.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>, bgardon@...gle.com,
        dmatlack@...gle.com, stevensd@...omium.org,
        kernel-team <kernel-team@...udflare.com>
Subject: Re: [PATCH 0/2] KVM: x86: Fix dangling page reference in TDP MMU

Just for the reference, here is my repro environment:

* kernel config:
https://gist.githubusercontent.com/ignatk/3a5457b8641d636963a2a4f14ccc854f/raw/e9b76b66454e4a3c0f7e395b1792b32ef053a541/gistfile1.txt
Kernel compiled from kvm/master. The config is processed with
mod2yesconfig, but when many things are modules - works too. I just
didn't want to bother with installing modules in the target VM.

* host: Debian Bullseye with qemu version: QEMU emulator version 6.1.0
(Debian 1:6.1+dfsg-6~bpo11+1)

* qemu commandline:
  qemu-system-x86_64 -nographic -cpu host \
                   -enable-kvm \
                   -machine q35 \
                   -smp 8 \
                   -m 8G \
                   -drive
if=pflash,format=raw,readonly=on,file=/usr/share/OVMF/OVMF_CODE.fd \
                   -drive
if=pflash,format=raw,file=/usr/share/OVMF/OVMF_VARS.fd \
                   -drive file=/work/rootfs.img,format=qcow2 \
                   -nic user,model=virtio-net-pci,hostfwd=tcp::22-:22 \
                   -kernel vmlinuz \
                   -append "console=ttyS0 root=/dev/sda rw
systemd.unified_cgroup_hierarchy=0"

* rootfs.img is barebones standard Debian Bullseye installation

* to install gvisor I just run the following in the VM (blindly
copypasted from https://gvisor.dev/docs/user_guide/install/):

(
  set -e
  ARCH=$(uname -m)
  URL=https://storage.googleapis.com/gvisor/releases/release/latest/${ARCH}
  wget ${URL}/runsc ${URL}/runsc.sha512 \
    ${URL}/containerd-shim-runsc-v1 ${URL}/containerd-shim-runsc-v1.sha512
  sha512sum -c runsc.sha512 \
    -c containerd-shim-runsc-v1.sha512
  rm -f *.sha512
  chmod a+rx runsc containerd-shim-runsc-v1
  sudo mv runsc containerd-shim-runsc-v1 /usr/local/bin
)

* to reproduce, just run "sudo runsc --platform=kvm --network=none do
echo ok" several times

Regards,
Ignat

On Mon, Dec 13, 2021 at 7:44 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Mon, Dec 13, 2021, Sean Christopherson wrote:
> > On Mon, Dec 13, 2021, Ignat Korchagin wrote:
> > > Unfortunately, this patchset does not fix the original issue reported in [1].
> >
> > Can you provide your kernel config?  And any other version/config info that might
> > be relevant, e.g. anything in gvisor or runsc?
>
> Scratch that, I've reproduced this, with luck I'll have a root cause by end of day.