[PATCH RFC v8 01/56] KVM: x86: Add 'fault_is_private' x86 op

[Michael Roth]

This callback is used by the KVM MMU to check whether a #NPF was for a
private GPA or not.

In some cases the full 64-bit error code for the #NPF will be needed to
make this determination, so also update kvm_mmu_do_page_fault() to
accept the full 64-bit value so it can be plumbed through to the
callback.

Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
 arch/x86/include/asm/kvm-x86-ops.h |  1 +
 arch/x86/include/asm/kvm_host.h    |  1 +
 arch/x86/kvm/mmu/mmu.c             |  3 +--
 arch/x86/kvm/mmu/mmu_internal.h    | 37 +++++++++++++++++++++++++++---
 4 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 8dc345cc6318..72183da010b8 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -131,6 +131,7 @@ KVM_X86_OP(msr_filter_changed)
 KVM_X86_OP(complete_emulated_msr)
 KVM_X86_OP(vcpu_deliver_sipi_vector)
 KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons);
+KVM_X86_OP_OPTIONAL_RET0(fault_is_private);
 
 #undef KVM_X86_OP
 #undef KVM_X86_OP_OPTIONAL
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e552374f2357..f856d689dda0 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1643,6 +1643,7 @@ struct kvm_x86_ops {
 
 	void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
 			     int root_level);
+	bool (*fault_is_private)(struct kvm *kvm, gpa_t gpa, u64 error_code, bool *private_fault);
 
 	bool (*has_wbinvd_exit)(void);
 
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index eda615f3951c..fb3f34b7391c 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5724,8 +5724,7 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err
 	}
 
 	if (r == RET_PF_INVALID) {
-		r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa,
-					  lower_32_bits(error_code), false);
+		r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa, error_code, false);
 		if (KVM_BUG_ON(r == RET_PF_INVALID, vcpu->kvm))
 			return -EIO;
 	}
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index e642d431df4b..557a001210df 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -231,6 +231,37 @@ struct kvm_page_fault {
 
 int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault);
 
+static bool kvm_mmu_fault_is_private(struct kvm *kvm, gpa_t gpa, u64 err)
+{
+	struct kvm_memory_slot *slot;
+	bool private_fault = false;
+	gfn_t gfn = gpa_to_gfn(gpa);
+
+	slot = gfn_to_memslot(kvm, gfn);
+	if (!slot) {
+		pr_debug("%s: no slot, GFN: 0x%llx\n", __func__, gfn);
+		goto out;
+	}
+
+	if (!kvm_slot_can_be_private(slot)) {
+		pr_debug("%s: slot is not private, GFN: 0x%llx\n", __func__, gfn);
+		goto out;
+	}
+
+	if (static_call(kvm_x86_fault_is_private)(kvm, gpa, err, &private_fault))
+		goto out;
+
+	/*
+	 * Handling below is for UPM self-tests and guests that treat userspace
+	 * as the authority on whether a fault should be private or not.
+	 */
+	private_fault = kvm_mem_is_private(kvm, gpa >> PAGE_SHIFT);
+
+out:
+	pr_debug("%s: GFN: 0x%llx, private: %d\n", __func__, gfn, private_fault);
+	return private_fault;
+}
+
 /*
  * Return values of handle_mmio_page_fault(), mmu.page_fault(), fast_page_fault(),
  * and of course kvm_mmu_do_page_fault().
@@ -262,11 +293,11 @@ enum {
 };
 
 static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
-					u32 err, bool prefetch)
+					u64 err, bool prefetch)
 {
 	struct kvm_page_fault fault = {
 		.addr = cr2_or_gpa,
-		.error_code = err,
+		.error_code = lower_32_bits(err),
 		.exec = err & PFERR_FETCH_MASK,
 		.write = err & PFERR_WRITE_MASK,
 		.present = err & PFERR_PRESENT_MASK,
@@ -280,7 +311,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 		.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),
+		.is_private = kvm_mmu_fault_is_private(vcpu->kvm, cr2_or_gpa, err),
 	};
 	int r;
 
-- 
2.25.1