linux-kernel - [PATCH v2 6/9] KVM: nSVM: trap #DB and #BP to userspace if guest debugging is on

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Date:   Thu,  7 May 2020 07:50:08 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     peterx@...hat.com
Subject: [PATCH v2 6/9] KVM: nSVM: trap #DB and #BP to userspace if guest debugging is on

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 90a1ca939627..adab5b1c5fe1 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -608,6 +608,11 @@ static int nested_svm_intercept_db(struct vcpu_svm *svm)
 {
 	unsigned long dr6;
 
+	/* Always catch it and pass it to userspace if debugging the guest.  */
+	if (svm->vcpu.guest_debug &
+	    (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))
+		return NESTED_EXIT_HOST;
+
 	/* if we're not singlestepping, it's not ours */
 	if (!svm->nmi_singlestep)
 		return NESTED_EXIT_DONE;
@@ -682,6 +687,9 @@ static int nested_svm_intercept(struct vcpu_svm *svm)
 		if (svm->nested.intercept_exceptions & excp_bits) {
 			if (exit_code == SVM_EXIT_EXCP_BASE + DB_VECTOR)
 				vmexit = nested_svm_intercept_db(svm);
+			else if (exit_code == SVM_EXIT_EXCP_BASE + BP_VECTOR &&
+				 svm->vcpu.guest_debug & KVM_GUESTDBG_USE_SW_BP)
+				vmexit = NESTED_EXIT_HOST;
 			else
 				vmexit = NESTED_EXIT_DONE;
 		}
-- 
2.18.2