KVM: x86: Clarify PMU related features bit manipulation

kvm_pmu_cpuid_update makes a lot of bit manuiplation operations, when in fact
there are already unions that can be used instead. Changing the bit
manipulation to the union for clarity. This patch does not change the
functionality.
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/pmu.c

@@ -15,6 +15,7 @@
 #include <linux/types.h>
 #include <linux/kvm_host.h>
 #include <linux/perf_event.h>
+#include <asm/perf_event.h>
 #include "x86.h"
 #include "cpuid.h"
 #include "lapic.h"
@@ -463,7 +464,8 @@ void kvm_pmu_cpuid_update(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = &vcpu->arch.pmu;
 	struct kvm_cpuid_entry2 *entry;
-	unsigned bitmap_len;
+	union cpuid10_eax eax;
+	union cpuid10_edx edx;
 
 	pmu->nr_arch_gp_counters = 0;
 	pmu->nr_arch_fixed_counters = 0;
@@ -475,25 +477,27 @@ void kvm_pmu_cpuid_update(struct kvm_vcpu *vcpu)
 	entry = kvm_find_cpuid_entry(vcpu, 0xa, 0);
 	if (!entry)
 		return;
+	eax.full = entry->eax;
+	edx.full = entry->edx;
 
-	pmu->version = entry->eax & 0xff;
+	pmu->version = eax.split.version_id;
 	if (!pmu->version)
 		return;
 
-	pmu->nr_arch_gp_counters = min((int)(entry->eax >> 8) & 0xff,
-			INTEL_PMC_MAX_GENERIC);
-	pmu->counter_bitmask[KVM_PMC_GP] =
-		((u64)1 << ((entry->eax >> 16) & 0xff)) - 1;
-	bitmap_len = (entry->eax >> 24) & 0xff;
-	pmu->available_event_types = ~entry->ebx & ((1ull << bitmap_len) - 1);
+	pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters,
+					INTEL_PMC_MAX_GENERIC);
+	pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << eax.split.bit_width) - 1;
+	pmu->available_event_types = ~entry->ebx &
+					((1ull << eax.split.mask_length) - 1);
 
 	if (pmu->version == 1) {
 		pmu->nr_arch_fixed_counters = 0;
 	} else {
-		pmu->nr_arch_fixed_counters = min((int)(entry->edx & 0x1f),
+		pmu->nr_arch_fixed_counters =
+			min_t(int, edx.split.num_counters_fixed,
 				INTEL_PMC_MAX_FIXED);
 		pmu->counter_bitmask[KVM_PMC_FIXED] =
-			((u64)1 << ((entry->edx >> 5) & 0xff)) - 1;
+			((u64)1 << edx.split.bit_width_fixed) - 1;
 	}
 
 	pmu->global_ctrl = ((1 << pmu->nr_arch_gp_counters) - 1) |