[PATCH v4 4/5] KVM: x86: let reexecute_instruction work for tdp

[Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>]

Currently, reexecute_instruction refused to retry all instructions. If
nested npt is used, the emulation may be caused by shadow page, it can
be fixed by dropping the shadow page

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
---
 arch/x86/kvm/x86.c |   28 ++++++++++++++++++++++------
 1 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ad39018..b0a3678 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4753,17 +4753,33 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu)
 	return r;
 }

-static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t gva)
+static bool reexecute_instruction(struct kvm_vcpu *vcpu, unsigned long cr2)
 {
-	gpa_t gpa;
+	gpa_t gpa = cr2;
 	pfn_t pfn;
+	unsigned int indirect_shadow_pages;
+
+	spin_lock(&vcpu->kvm->mmu_lock);
+	indirect_shadow_pages = vcpu->kvm->arch.indirect_shadow_pages;
+	spin_unlock(&vcpu->kvm->mmu_lock);

-	if (tdp_enabled)
+	if (!indirect_shadow_pages)
 		return false;

-	gpa = kvm_mmu_gva_to_gpa_read(vcpu, gva, NULL);
-	if (gpa == UNMAPPED_GVA)
-		return true; /* let cpu generate fault */
+	if (!vcpu->arch.mmu.direct_map) {
+		/*
+		 * Write permission should be allowed since only
+		 * write access need to be emulated.
+		 */
+		gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2, NULL);
+
+		/*
+		 * If the mapping is invalid in guest, let cpu retry
+		 * it to generate fault.
+		 */
+		if (gpa == UNMAPPED_GVA)
+			return true;
+	}

 	/*
 	 * if emulation was due to access to shadowed page table
-- 
1.7.7.6