Re: [PATCH] KVM: nvmx: retry writing guest memory after page fault injected

[Liran Alon]

> On 25 Dec 2019, at 4:21, linmiaohe <linmiaohe@xxxxxxxxxx> wrote:
> 
> From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> 
> We should retry writing guest memory when kvm_write_guest_virt_system()
> failed and page fault is injected in handle_vmread().
> 
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>

Patch fix seems correct to me:
Reviewed-by: Liran Alon <liran.alon@xxxxxxxxxx>

However, I suggest to rephrase commit title & message as follows:

"""
KVM: nVMX: vmread should not set rflags to specify success in case of #PF

In case writing to vmread destination operand result in a #PF, vmread should
not call nested_vmx_succeed() to set rflags to specify success. Similar to as
done in for VMPTRST (See handle_vmptrst()).
"""

In addition, it will be appreciated if you would also submit kvm-unit-test that verifies this condition.

-Liran

> ---
> arch/x86/kvm/vmx/nested.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 8edefdc9c0cb..c1ec9f25a417 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -4799,8 +4799,10 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
> 					instr_info, true, len, &gva))
> 			return 1;
> 		/* _system ok, nested_vmx_check_permission has verified cpl=0 */
> -		if (kvm_write_guest_virt_system(vcpu, gva, &value, len, &e))
> +		if (kvm_write_guest_virt_system(vcpu, gva, &value, len, &e)) {
> 			kvm_inject_page_fault(vcpu, &e);
> +			return 1;
> +		}
> 	}
> 
> 	return nested_vmx_succeed(vcpu);
> -- 
> 2.19.1
>