Re: [PATCH 4/8] KVM: SVM: Stuff next_rip on emualted INT3 injection if NRIPS is supported

From: Maxim Levitsky <mlevitsk@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Maciej S . Szmigiero" <maciej.szmigiero@oracle.com>
Subject: Re: [PATCH 4/8] KVM: SVM: Stuff next_rip on emualted INT3 injection if NRIPS is supported
Date: Mon, 04 Apr 2022 15:00:01 +0300	[thread overview]
Message-ID: <5752e461f5912d4312eb63f1b7f521f54ab40f79.camel@redhat.com> (raw)
In-Reply-To: <20220402010903.727604-5-seanjc@google.com>

On Sat, 2022-04-02 at 01:08 +0000, Sean Christopherson wrote:
> If NRIPS is supported in hardware but disabled in KVM, set next_rip to
> the next RIP when advancing RIP as part of emulating INT3 injection.
> There is no flag to tell the CPU that KVM isn't using next_rip, and so
> leaving next_rip is left as is will result in the CPU pushing garbage
> onto the stack when vectoring the injected event.
> 
> Fixes: 66b7138f9136 ("KVM: SVM: Emulate nRIP feature when reinjecting INT3")
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  arch/x86/kvm/svm/svm.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 30cef3b10838..6ea8f16e39ac 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -391,6 +391,10 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu)
>  		 */
>  		(void)svm_skip_emulated_instruction(vcpu);
>  		rip = kvm_rip_read(vcpu);
> +
> +		if (boot_cpu_has(X86_FEATURE_NRIPS))
> +			svm->vmcb->control.next_rip = rip;
> +
>  		svm->int3_rip = rip + svm->vmcb->save.cs.base;
>  		svm->int3_injected = rip - old_rip;
>  	}

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
	Maxim Levitsky