KVM: x86: Add helper functions for illegal GPA checking and page fault injection

This patch adds two helper functions that will be used to support virtualizing
MAXPHYADDR in both kvm-intel.ko and kvm.ko.

kvm_fixup_and_inject_pf_error() injects a page fault for a user-specified GVA,
while kvm_mmu_is_illegal_gpa() checks whether a GPA exceeds vCPU address limits.

Signed-off-by: Mohammed Gamal <mgamal@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200710154811.418214-2-mgamal@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.h

@@ -4,6 +4,7 @@
 
 #include <linux/kvm_host.h>
 #include "kvm_cache_regs.h"
+#include "cpuid.h"
 
 #define PT64_PT_BITS 9
 #define PT64_ENT_PER_PAGE (1 << PT64_PT_BITS)
@@ -150,6 +151,11 @@ static inline bool is_write_protection(struct kvm_vcpu *vcpu)
 	return kvm_read_cr0_bits(vcpu, X86_CR0_WP);
 }
 
+static inline bool kvm_mmu_is_illegal_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
+{
+        return (gpa >= BIT_ULL(cpuid_maxphyaddr(vcpu)));
+}
+
 /*
  * Check if a given access (described through the I/D, W/R and U/S bits of a
  * page fault error code pfec) causes a permission fault with the given PTE

arch/x86/kvm/x86.c

@@ -10738,6 +10738,27 @@ int kvm_spec_ctrl_test_value(u64 value)
 }
 EXPORT_SYMBOL_GPL(kvm_spec_ctrl_test_value);
 
+void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code)
+{
+	struct x86_exception fault;
+
+	if (!(error_code & PFERR_PRESENT_MASK) ||
+	    vcpu->arch.walk_mmu->gva_to_gpa(vcpu, gva, error_code, &fault) != UNMAPPED_GVA) {
+		/*
+		 * If vcpu->arch.walk_mmu->gva_to_gpa succeeded, the page
+		 * tables probably do not match the TLB.  Just proceed
+		 * with the error code that the processor gave.
+		 */
+		fault.vector = PF_VECTOR;
+		fault.error_code_valid = true;
+		fault.error_code = error_code;
+		fault.nested_page_fault = false;
+		fault.address = gva;
+	}
+	vcpu->arch.walk_mmu->inject_page_fault(vcpu, &fault);
+}
+EXPORT_SYMBOL_GPL(kvm_fixup_and_inject_pf_error);
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);

arch/x86/kvm/x86.h

@@ -272,6 +272,7 @@ int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
 bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
 					  int page_num);
 bool kvm_vector_hashing_enabled(void);
+void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code);
 int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			    int emulation_type, void *insn, int insn_len);
 fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);