[RFC PATCH v4 04/10] KVM: x86: Introduce PFERR_GUEST_ENC_MASK to indicate fault is private

[isaku . yamahata]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

Add two PFERR codes to designate that the page fault is private and that
it requires looking up memory attributes.  The vendor kvm page fault
handler should set PFERR_GUEST_ENC_MASK bit based on their fault
information.  It may or may not use the hardware value directly or
parse the hardware value to set the bit.

For KVM_X86_PROTECTED_VM, ask memory attributes for the fault privateness.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

---
Changes v3 -> v4:
- rename back struct kvm_page_fault::private => is_private
- catch up rename: KVM_X86_PROTECTED_VM => KVM_X86_SW_PROTECTED_VM

Changes v2 -> v3:
- Revive PFERR_GUEST_ENC_MASK
- rename struct kvm_page_fault::is_private => private
- Add check KVM_X86_PROTECTED_VM

Changes v1 -> v2:
- Introduced fault type and replaced is_private with fault_type.
- Add kvm_get_fault_type() to encapsulate the difference.
---
 arch/x86/include/asm/kvm_host.h |  2 ++
 arch/x86/kvm/mmu/mmu.c          |  8 ++++++--
 arch/x86/kvm/mmu/mmu_internal.h | 14 +++++++++++++-
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2c9350aa0da4..ab7d080bf544 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -255,6 +255,7 @@ enum x86_intercept_stage;
 #define PFERR_SGX_BIT 15
 #define PFERR_GUEST_FINAL_BIT 32
 #define PFERR_GUEST_PAGE_BIT 33
+#define PFERR_GUEST_ENC_BIT 34
 #define PFERR_IMPLICIT_ACCESS_BIT 48
 
 #define PFERR_PRESENT_MASK	BIT(PFERR_PRESENT_BIT)
@@ -266,6 +267,7 @@ enum x86_intercept_stage;
 #define PFERR_SGX_MASK		BIT(PFERR_SGX_BIT)
 #define PFERR_GUEST_FINAL_MASK	BIT_ULL(PFERR_GUEST_FINAL_BIT)
 #define PFERR_GUEST_PAGE_MASK	BIT_ULL(PFERR_GUEST_PAGE_BIT)
+#define PFERR_GUEST_ENC_MASK	BIT_ULL(PFERR_GUEST_ENC_BIT)
 #define PFERR_IMPLICIT_ACCESS	BIT_ULL(PFERR_IMPLICIT_ACCESS_BIT)
 
 #define PFERR_NESTED_GUEST_PAGE (PFERR_GUEST_PAGE_MASK |	\
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index a2fe091e327a..d2ebe26fb822 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4399,8 +4399,12 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 			return RET_PF_EMULATE;
 	}
 
-	if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn))
-		return kvm_do_memory_fault_exit(vcpu, fault);
+	if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn)) {
+		if (vcpu->kvm->arch.vm_type == KVM_X86_SW_PROTECTED_VM)
+			return RET_PF_RETRY;
+		else
+			return kvm_do_memory_fault_exit(vcpu, fault);
+	}
 
 	if (fault->is_private)
 		return kvm_faultin_pfn_private(vcpu, fault);
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 7f9ec1e5b136..4f8f83546c37 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -282,6 +282,18 @@ enum {
 	RET_PF_SPURIOUS,
 };
 
+static inline bool kvm_is_fault_private(struct kvm *kvm, gpa_t gpa, u64 error_code)
+{
+	/*
+	 * This is racy with mmu_seq.  If we hit a race, it would result in a
+	 * spurious KVM_EXIT_MEMORY_FAULT.
+	 */
+	if (kvm->arch.vm_type == KVM_X86_SW_PROTECTED_VM)
+		return kvm_mem_is_private(kvm, gpa_to_gfn(gpa));
+
+	return error_code & PFERR_GUEST_ENC_MASK;
+}
+
 static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 					u64 err, bool prefetch, int *emulation_type)
 {
@@ -295,13 +307,13 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 		.user = err & PFERR_USER_MASK,
 		.prefetch = prefetch,
 		.is_tdp = likely(vcpu->arch.mmu->page_fault == kvm_tdp_page_fault),
+		.is_private = kvm_is_fault_private(vcpu->kvm, cr2_or_gpa, err),
 		.nx_huge_page_workaround_enabled =
 			is_nx_huge_page_enabled(vcpu->kvm),
 
 		.max_level = KVM_MAX_HUGEPAGE_LEVEL,
 		.req_level = PG_LEVEL_4K,
 		.goal_level = PG_LEVEL_4K,
-		.is_private = kvm_mem_is_private(vcpu->kvm, cr2_or_gpa >> PAGE_SHIFT),
 	};
 	int r;
 
-- 
2.25.1