KVM: x86: Add helper to consolidate "raw" reserved GPA mask calculations

Add a helper to generate the mask of reserved GPA bits _without_ any
adjustments for repurposed bits, and use it to replace a variety of
open coded variants in the MTRR and APIC_BASE flows.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210204000117.3303214-11-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/cpuid.c

@@ -173,7 +173,7 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 	kvm_update_pv_runtime(vcpu);
 
 	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
-	vcpu->arch.reserved_gpa_bits = rsvd_bits(cpuid_maxphyaddr(vcpu), 63);
+	vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu);
 
 	kvm_pmu_refresh(vcpu);
 	vcpu->arch.cr4_guest_rsvd_bits =
@@ -227,6 +227,16 @@ int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu)
 	return 36;
 }
 
+/*
+ * This "raw" version returns the reserved GPA bits without any adjustments for
+ * encryption technologies that usurp bits.  The raw mask should be used if and
+ * only if hardware does _not_ strip the usurped bits, e.g. in virtual MTRRs.
+ */
+u64 kvm_vcpu_reserved_gpa_bits_raw(struct kvm_vcpu *vcpu)
+{
+	return rsvd_bits(cpuid_maxphyaddr(vcpu), 63);
+}
+
 /* when an old userspace process fills a new kernel module */
 int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 			     struct kvm_cpuid *cpuid,

arch/x86/kvm/cpuid.h

@@ -30,6 +30,7 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
 	       u32 *ecx, u32 *edx, bool exact_only);
 
 int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu);
+u64 kvm_vcpu_reserved_gpa_bits_raw(struct kvm_vcpu *vcpu);
 
 static inline int cpuid_maxphyaddr(struct kvm_vcpu *vcpu)
 {

arch/x86/kvm/mtrr.c

@@ -75,7 +75,7 @@ bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 	/* variable MTRRs */
 	WARN_ON(!(msr >= 0x200 && msr < 0x200 + 2 * KVM_NR_VAR_MTRR));
 
-	mask = (~0ULL) << cpuid_maxphyaddr(vcpu);
+	mask = kvm_vcpu_reserved_gpa_bits_raw(vcpu);
 	if ((msr & 1) == 0) {
 		/* MTRR base */
 		if (!valid_mtrr_type(data & 0xff))
@@ -351,14 +351,14 @@ static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 	if (var_mtrr_range_is_valid(cur))
 		list_del(&mtrr_state->var_ranges[index].node);
 
-	/* Extend the mask with all 1 bits to the left, since those
-	 * bits must implicitly be 0.  The bits are then cleared
-	 * when reading them.
+	/*
+	 * Set all illegal GPA bits in the mask, since those bits must
+	 * implicitly be 0.  The bits are then cleared when reading them.
 	 */
 	if (!is_mtrr_mask)
 		cur->base = data;
 	else
-		cur->mask = data | (-1LL << cpuid_maxphyaddr(vcpu));
+		cur->mask = data | kvm_vcpu_reserved_gpa_bits_raw(vcpu);
 
 	/* add it to the list if it's enabled. */
 	if (var_mtrr_range_is_valid(cur)) {
@@ -426,7 +426,7 @@ int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 		else
 			*pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;
 
-		*pdata &= (1ULL << cpuid_maxphyaddr(vcpu)) - 1;
+		*pdata &= ~kvm_vcpu_reserved_gpa_bits_raw(vcpu);
 	}
 
 	return 0;

arch/x86/kvm/x86.c

@@ -407,7 +407,7 @@ int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
 	enum lapic_mode old_mode = kvm_get_apic_mode(vcpu);
 	enum lapic_mode new_mode = kvm_apic_mode(msr_info->data);
-	u64 reserved_bits = ((~0ULL) << cpuid_maxphyaddr(vcpu)) | 0x2ff |
+	u64 reserved_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu) | 0x2ff |
 		(guest_cpuid_has(vcpu, X86_FEATURE_X2APIC) ? 0 : X2APIC_ENABLE);
 
 	if ((msr_info->data & reserved_bits) != 0 || new_mode == LAPIC_MODE_INVALID)
@@ -10078,7 +10078,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
 	fx_init(vcpu);
 
 	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
-	vcpu->arch.reserved_gpa_bits = rsvd_bits(cpuid_maxphyaddr(vcpu), 63);
+	vcpu->arch.reserved_gpa_bits = kvm_vcpu_reserved_gpa_bits_raw(vcpu);
 
 	vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;