Re: [PATCH][resend] KVM: x86: check steal time address when enable steal time

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Li RongQing <lirongqing@baidu.com> writes:

> check steal time address when enable steal time, do not update
> arch.st.msr_val if the address is invalid,  and return in #GP
>
> this can avoid unnecessary write/read invalid memory when guest
> is running
>
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> ---
>  arch/x86/kvm/x86.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index eb402966..3ed0949 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3616,6 +3616,9 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		if (data & KVM_STEAL_RESERVED_MASK)
>  			return 1;
>  
> +		if (!kvm_vcpu_gfn_to_memslot(vcpu, data >> PAGE_SHIFT))
> +			return 1;
> +

What about we use stronger kvm_is_visible_gfn() instead? I didn't put
much thought to what's going to happen if we put e.g. APIC access page
addr to the MSR, let's just cut any possibility.

>  		vcpu->arch.st.msr_val = data;
>  
>  		if (!(data & KVM_MSR_ENABLED))

-- 
Vitaly