KVM: x86/mmu: Pass full 64-bit error code when handling page faults

Plumb the full 64-bit error code throughout the page fault handling code
so that KVM can use the upper 32 bits, e.g. SNP's PFERR_GUEST_ENC_MASK
will be used to determine whether or not a fault is private vs. shared.

Note, passing the 64-bit error code to FNAME(walk_addr)() does NOT change
the behavior of permission_fault() when invoked in the page fault path, as
KVM explicitly clears PFERR_IMPLICIT_ACCESS in kvm_mmu_page_fault().

Continue passing '0' from the async #PF worker, as guest_memfd and thus
private memory doesn't support async page faults.
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
[mdr: drop references/changes on rebase, update commit message]
Signed-off-by: Michael Roth <michael.roth@amd.com>
[sean: drop truncation in call to FNAME(walk_addr)(), rewrite changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <20240228024147.41573-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -5799,8 +5799,7 @@ 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,
 					  &emulation_type);
 		if (KVM_BUG_ON(r == RET_PF_INVALID, vcpu->kvm))
 			return -EIO;

arch/x86/kvm/mmu/mmu_internal.h

@@ -190,7 +190,7 @@ static inline bool is_nx_huge_page_enabled(struct kvm *kvm)
 struct kvm_page_fault {
 	/* arguments to kvm_mmu_do_page_fault.  */
 	const gpa_t addr;
-	const u32 error_code;
+	const u64 error_code;
 	const bool prefetch;
 
 	/* Derived from error_code.  */
@@ -288,7 +288,7 @@ static inline void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
 }
 
 static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
-					u32 err, bool prefetch, int *emulation_type)
+					u64 err, bool prefetch, int *emulation_type)
 {
 	struct kvm_page_fault fault = {
 		.addr = cr2_or_gpa,

arch/x86/kvm/mmu/mmutrace.h

@@ -260,7 +260,7 @@ TRACE_EVENT(
 	TP_STRUCT__entry(
 		__field(int, vcpu_id)
 		__field(gpa_t, cr2_or_gpa)
-		__field(u32, error_code)
+		__field(u64, error_code)
 		__field(u64 *, sptep)
 		__field(u64, old_spte)
 		__field(u64, new_spte)