KVM: x86: rdpmc emulation checks the counter incorrectly

The rdpmc emulation checks that the counter (ECX) is not higher than 2, without
taking into considerations bits 30:31 role (e.g., bit 30 marks whether the
counter is fixed). The fix uses the pmu information for checking the validity
of the pmu counter.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_emulate.h

@@ -194,6 +194,7 @@ struct x86_emulate_ops {
 	int (*set_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong value);
 	int (*set_msr)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 data);
 	int (*get_msr)(struct x86_emulate_ctxt *ctxt, u32 msr_index, u64 *pdata);
+	int (*check_pmc)(struct x86_emulate_ctxt *ctxt, u32 pmc);
 	int (*read_pmc)(struct x86_emulate_ctxt *ctxt, u32 pmc, u64 *pdata);
 	void (*halt)(struct x86_emulate_ctxt *ctxt);
 	void (*wbinvd)(struct x86_emulate_ctxt *ctxt);

arch/x86/include/asm/kvm_host.h

@@ -1070,6 +1070,7 @@ void kvm_pmu_cpuid_update(struct kvm_vcpu *vcpu);
 bool kvm_pmu_msr(struct kvm_vcpu *vcpu, u32 msr);
 int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *data);
 int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
+int kvm_pmu_check_pmc(struct kvm_vcpu *vcpu, unsigned pmc);
 int kvm_pmu_read_pmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
 void kvm_handle_pmu_event(struct kvm_vcpu *vcpu);
 void kvm_deliver_pmi(struct kvm_vcpu *vcpu);

arch/x86/kvm/emulate.c

@@ -3507,7 +3507,7 @@ static int check_rdpmc(struct x86_emulate_ctxt *ctxt)
 	u64 rcx = reg_read(ctxt, VCPU_REGS_RCX);
 
 	if ((!(cr4 & X86_CR4_PCE) && ctxt->ops->cpl(ctxt)) ||
-	    (rcx > 3))
+	    ctxt->ops->check_pmc(ctxt, rcx))
 		return emulate_gp(ctxt, 0);
 
 	return X86EMUL_CONTINUE;

arch/x86/kvm/pmu.c

@@ -428,6 +428,15 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	return 1;
 }
 
+int kvm_pmu_check_pmc(struct kvm_vcpu *vcpu, unsigned pmc)
+{
+	struct kvm_pmu *pmu = &vcpu->arch.pmu;
+	bool fixed = pmc & (1u << 30);
+	pmc &= ~(3u << 30);
+	return (!fixed && pmc >= pmu->nr_arch_gp_counters) ||
+		(fixed && pmc >= pmu->nr_arch_fixed_counters);
+}
+
 int kvm_pmu_read_pmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data)
 {
 	struct kvm_pmu *pmu = &vcpu->arch.pmu;

arch/x86/kvm/x86.c

@@ -4762,6 +4762,12 @@ static int emulator_set_msr(struct x86_emulate_ctxt *ctxt,
 	return kvm_set_msr(emul_to_vcpu(ctxt), &msr);
 }
 
+static int emulator_check_pmc(struct x86_emulate_ctxt *ctxt,
+			      u32 pmc)
+{
+	return kvm_pmu_check_pmc(emul_to_vcpu(ctxt), pmc);
+}
+
 static int emulator_read_pmc(struct x86_emulate_ctxt *ctxt,
 			     u32 pmc, u64 *pdata)
 {
@@ -4838,6 +4844,7 @@ static const struct x86_emulate_ops emulate_ops = {
 	.set_dr              = emulator_set_dr,
 	.set_msr             = emulator_set_msr,
 	.get_msr             = emulator_get_msr,
+	.check_pmc	     = emulator_check_pmc,
 	.read_pmc            = emulator_read_pmc,
 	.halt                = emulator_halt,
 	.wbinvd              = emulator_wbinvd,