Re: [PATCH] target-i386: check vcpu features before accessing MSR_TSC_AUX

[Haozhong Zhang <haozhong.zhang@intel.com>]

On 12/14/15 12:51, Paolo Bonzini wrote:
> 
> 
> On 14/12/2015 12:07, Haozhong Zhang wrote:
> > This patch fix a bug that prevents VM rebooting on recent versions of
> > KVM (from commit 9dbe6cf).
> > 
> > kvm_get_msrs() is called to save guest MSR_TSC_AUX and other MSRs across
> > rebooting. It only checks whether KVM exposes MSR_TSC_AUX to userspace.
> > However, if vcpu does not support rdtscp (e.g. kvm64), current KVM will
> > fail the saving and thus all other MSRs following it will fail in
> > kvm_get_msrs(). As a result, from KVM commit 9dbe6cf that exposes
> > MSR_TSC_AUX, VM can not successfully reboot.
> > 
> > This patch fixes this bug by adding the missing rdtscp feature checks.
> 
> That commit is not in any released kernel.

Right, it's currently only in kvm next. But I assume it would finally come
into a released kernel.

> It's better if we just check
> msr_info->host_initiated in vmx_get_msr and vmx_set_msr. Can you prepare
> a patch?
>

Yes, I'll send a KVM patch later. And then this QEMU patch is not
needed any more.

Haozhong