Re: [Qemu-devel] [PATCH] i386/kvm: mask MSR_IA32_BNDCFGS if MPX is not enabled in guest cpuid

[Haozhong Zhang]

On 07/03/17 17:45 +0200, Paolo Bonzini wrote:
> 
> 
> On 03/07/2017 17:23, Haozhong Zhang wrote:
> > Otherwise, QEMU on a host with MPX support will try to set guest
> > MSR_IA32_BNDCFGS although guest MPX is not enabled, and result in
> > abort.
> > 
> > For example,
> >    qemu-system-x86_64 -enable-kvm -cpu qemu64,-mpx ...
> > aborts with messages:
> >    qemu-system-x86_64: error: failed to set MSR 0xd90 to 0x0
> >    qemu-system-x86_64: /root/qemu.git/target/i386/kvm.c:1832: kvm_put_msrs: 
> > Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed
> 
> I think the fix should be in KVM, allowing BNDCFGS = 0 if
> host_initiated, even if MPX is not enabled.
> 

Agree. I've sent a KVM patch to fix this issue.

Thanks,
Haozhong