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From:   "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
To:     Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>
Cc:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v3 04/12] KVM: SVM: Stuff next_rip on emulated INT3 injection if NRIPS is supported
Date:   Mon,  2 May 2022 00:07:28 +0200
Message-Id: <cd328309a3b88604daa2359ad56f36cb565ce2d4.1651440202.git.maciej.szmigiero@oracle.com>
In-Reply-To: <cover.1651440202.git.maciej.szmigiero@oracle.com>
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From: Sean Christopherson <seanjc@google.com>

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.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Fixes: 66b7138f9136 ("KVM: SVM: Emulate nRIP feature when reinjecting INT3")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
 arch/x86/kvm/svm/svm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 1a719f47a964..a05a4e521400 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -392,6 +392,10 @@ 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;
 	}
@@ -3701,7 +3705,7 @@ static void svm_complete_interrupts(struct kvm_vcpu *vcpu)
 	/*
 	 * If NextRIP isn't enabled, KVM must manually advance RIP prior to
 	 * injecting the soft exception/interrupt.  That advancement needs to
-	 * be unwound if vectoring didn't complete.  Note, the _new_ event may
+	 * be unwound if vectoring didn't complete.  Note, the new event may
 	 * not be the injected event, e.g. if KVM injected an INTn, the INTn
 	 * hit a #NP in the guest, and the #NP encountered a #PF, the #NP will
 	 * be the reported vectored event, but RIP still needs to be unwound.