target/i386/kvm/kvm.c:2996: kvm_buf_set_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed

From: Michael Tokarev <mjt@tls.msk.ru>
To: QEMU Developers <qemu-devel@nongnu.org>
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Subject: target/i386/kvm/kvm.c:2996: kvm_buf_set_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed
Date: Fri, 22 Apr 2022 20:47:16 +0300	[thread overview]
Message-ID: <4c1c558a-5e71-b15c-4927-04d0ad68432d@msgid.tls.msk.ru> (raw)

Hi!

Apparently there's an assertion failure like in $subj in qemu-7.0.0
(it didn't happen with qemu-6.2), even after the commit:

commit e910a53fb4f20aa012e46371ffb4c32c8da259b4
Author: Maxim Levitsky <mlevitsk@redhat.com>
Date:   Wed Feb 23 13:56:49 2022 +0200

     KVM: x86: nSVM: disallow userspace setting of MSR_AMD64_TSC_RATIO to non default value when tsc scaling disabled

is included in the kernel build.

The original debian bugreport: https://bugs.debian.org/1010026

The logs from libvirt with 2 kernels which have the said commit
included: (based on 5.16.18 and 5.17.3 - unfortunately the kernel
release reported there is difficult):
  https://bugs.debian.org/1010026#42

Both ends up with

qemu-system-x86_64: error: failed to set MSR 0xc0000104 to 0x100000000
qemu-system-x86_64: ../../target/i386/kvm/kvm.c:2996: kvm_buf_set_msrs:
  Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.

I wonder if there's something else needs to be fixed..

BTW, commit e910a53fb4f20aa012e46 included a bugfix for qemu 6.2, -
maybe we should not accumulate fixes for other software bugs in
kernel?  That's just a thought, nothing more..

Thanks!

/mjt