From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: KVM: x86: do not retain disabled or invalid pvclock address
Date: Sun, 09 Sep 2012 17:08:31 +0300
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References: <20120823111654.GA18057@amt.cnet>
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Cc: kvm <kvm@vger.kernel.org>
To: Marcelo Tosatti <mtosatti@redhat.com>
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On 08/23/2012 02:16 PM, Marcelo Tosatti wrote:
> 
> In case an invalid or disabled gpa is written to the SYSTEM_TIME
> MSR, do not retain its value. This is not documented behaviour, 
> nor should be supported.
> 
> Also clear it on system reset. Not doing so can hide bugs.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e00050c..ed4bfb7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1528,6 +1528,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
>  
>  static void kvmclock_reset(struct kvm_vcpu *vcpu)
>  {
> +	vcpu->arch.time = 0;
>  	if (vcpu->arch.time_page) {
>  		kvm_release_page_dirty(vcpu->arch.time_page);
>  		vcpu->arch.time_page = NULL;
> @@ -1632,8 +1633,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  		kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
>  
>  		/* we verify if the enable bit is set... */
> -		if (!(data & 1))
> +		if (!(data & 1)) {
> +			vcpu->arch.time = 0;

Should we not just assign data to vcpu->arch.time?  That's how the real
MSRs work.

>  			break;
> +		}
>  
>  		/* ...but clean it before doing the actual write */
>  		vcpu->arch.time_offset = data & ~(PAGE_MASK | 1);
> @@ -1641,8 +1644,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  		vcpu->arch.time_page =
>  				gfn_to_page(vcpu->kvm, data >> PAGE_SHIFT);
>  
> -		if (is_error_page(vcpu->arch.time_page))
> +		if (is_error_page(vcpu->arch.time_page)) {
>  			vcpu->arch.time_page = NULL;
> +			vcpu->arch.time = 0;
> +		}
>  

Don't see why.


-- 
error compiling committee.c: too many arguments to function