linux-kernel - [PATCH] KVM: SVM: limit kvm_handle_page

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Date:   Tue, 10 Oct 2017 10:49:43 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Brijesh Singh <brijesh.singh@....com>
Subject: [PATCH] KVM: SVM: limit kvm_handle_page_fault to #PF handling

It has always annoyed me a bit how SVM_EXIT_NPF is handled by
pf_interception.  This is also the only reason behind the
under-documented need_unprotect argument to kvm_handle_page_fault.
Let NPF go straight to kvm_mmu_page_fault, just like VMX
does in handle_ept_violation and handle_ept_misconfig.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/mmu.c |  5 ++---
 arch/x86/kvm/mmu.h |  3 +--
 arch/x86/kvm/svm.c | 15 +++++++++++++--
 arch/x86/kvm/vmx.c |  3 +--
 4 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index d6fba5684ca8..1706683d5fd7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3820,8 +3820,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
 }
 
 int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
-				u64 fault_address, char *insn, int insn_len,
-				bool need_unprotect)
+				u64 fault_address, char *insn, int insn_len)
 {
 	int r = 1;
 
@@ -3829,7 +3828,7 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
 	default:
 		trace_kvm_page_fault(fault_address, error_code);
 
-		if (need_unprotect && kvm_event_needs_reinjection(vcpu))
+		if (kvm_event_needs_reinjection(vcpu))
 			kvm_mmu_unprotect_page_virt(vcpu, fault_address);
 		r = kvm_mmu_page_fault(vcpu, fault_address, error_code, insn,
 				insn_len);
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 64a2dbd2b1af..1092302aa16a 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -65,8 +65,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
 			     bool accessed_dirty);
 bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu);
 int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
-				u64 fault_address, char *insn, int insn_len,
-				bool need_unprotect);
+				u64 fault_address, char *insn, int insn_len);
 
 static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm)
 {
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0e68f0b3cbf7..01e6e8fab5d6 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2144,7 +2144,18 @@ static int pf_interception(struct vcpu_svm *svm)
 
 	return kvm_handle_page_fault(&svm->vcpu, error_code, fault_address,
 			svm->vmcb->control.insn_bytes,
-			svm->vmcb->control.insn_len, !npt_enabled);
+			svm->vmcb->control.insn_len);
+}
+
+static int npf_interception(struct vcpu_svm *svm)
+{
+	u64 fault_address = svm->vmcb->control.exit_info_2;
+	u64 error_code = svm->vmcb->control.exit_info_1;
+
+	trace_kvm_page_fault(fault_address, error_code);
+	return kvm_mmu_page_fault(&svm->vcpu, error_code, fault_address,
+			svm->vmcb->control.insn_bytes,
+			svm->vmcb->control.insn_len);
 }
 
 static int db_interception(struct vcpu_svm *svm)
@@ -4131,7 +4142,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
 	[SVM_EXIT_MONITOR]			= monitor_interception,
 	[SVM_EXIT_MWAIT]			= mwait_interception,
 	[SVM_EXIT_XSETBV]			= xsetbv_interception,
-	[SVM_EXIT_NPF]				= pf_interception,
+	[SVM_EXIT_NPF]				= npf_interception,
 	[SVM_EXIT_RSM]                          = emulate_on_interception,
 	[SVM_EXIT_AVIC_INCOMPLETE_IPI]		= avic_incomplete_ipi_interception,
 	[SVM_EXIT_AVIC_UNACCELERATED_ACCESS]	= avic_unaccelerated_access_interception,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 74582375e0be..c9214e3a01df 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5894,8 +5894,7 @@ static int handle_exception(struct kvm_vcpu *vcpu)
 		cr2 = vmcs_readl(EXIT_QUALIFICATION);
 		/* EPT won't cause page fault directly */
 		WARN_ON_ONCE(!vcpu->arch.apf.host_apf_reason && enable_ept);
-		return kvm_handle_page_fault(vcpu, error_code, cr2, NULL, 0,
-				true);
+		return kvm_handle_page_fault(vcpu, error_code, cr2, NULL, 0);
 	}
 
 	ex_no = intr_info & INTR_INFO_VECTOR_MASK;
-- 
1.8.3.1