linux-kernel - [PATCH RESEND 1/3] KVM: SVM: Get rid of handle_fastpath_set_msr

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Date:   Wed,  9 Sep 2020 10:57:15 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        "Paul K ." <kronenpj@...nenpj.dyndns.org>,
        "# v5 . 8-rc1+" <stable@...r.kernel.org>
Subject: [PATCH RESEND 1/3] KVM: SVM: Get rid of handle_fastpath_set_msr_irqoff()

From: Wanpeng Li <wanpengli@...cent.com>

Analysis from Sean:

 | svm->next_rip is reset in svm_vcpu_run() only after calling 
 | svm_exit_handlers_fastpath(), which will cause SVM's 
 | skip_emulated_instruction() to write a stale RIP.
 
Let's get rid of handle_fastpath_set_msr_irqoff() in svm_exit_handlers_fastpath()
to have a quick fix.

Reported-by: Paul K. <kronenpj@...nenpj.dyndns.org>
Suggested-by: Sean Christopherson <sean.j.christopherson@...el.com>
Cc: Paul K. <kronenpj@...nenpj.dyndns.org>
Cc: <stable@...r.kernel.org> # v5.8-rc1+
Fixes: 404d5d7bff0d (KVM: X86: Introduce more exit_fastpath_completion enum values)
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/kvm/svm/svm.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 19e622a..c61bc3b 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3349,11 +3349,6 @@ static void svm_cancel_injection(struct kvm_vcpu *vcpu)
 
 static fastpath_t svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
 {
-	if (!is_guest_mode(vcpu) &&
-	    to_svm(vcpu)->vmcb->control.exit_code == SVM_EXIT_MSR &&
-	    to_svm(vcpu)->vmcb->control.exit_info_1)
-		return handle_fastpath_set_msr_irqoff(vcpu);
-
 	return EXIT_FASTPATH_NONE;
 }
 
-- 
2.7.4