[PATCH 03/26] KVM: x86: Snapshot MSR index in a local variable when processing lists

From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 03/26] KVM: x86: Snapshot MSR index in a local variable when processing lists
Date: Wed, 29 Jan 2020 15:46:17 -0800	[thread overview]
Message-ID: <20200129234640.8147-4-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20200129234640.8147-1-sean.j.christopherson@intel.com>

Snapshot the MSR index when processing the virtualized and emulated MSR
lists in kvm_init_msr_list() to improve code readability, particularly
in the RTIT and PerfMon MSR checks.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/x86.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 24597526b5de..3d4a5326d84e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5214,7 +5214,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
 static void kvm_init_msr_list(void)
 {
 	struct x86_pmu_capability x86_pmu;
-	u32 dummy[2];
+	u32 dummy[2], msr_index;
 	unsigned i;
 
 	BUILD_BUG_ON_MSG(INTEL_PMC_MAX_FIXED != 4,
@@ -5227,14 +5227,16 @@ static void kvm_init_msr_list(void)
 	num_msr_based_features = 0;
 
 	for (i = 0; i < ARRAY_SIZE(msrs_to_save_all); i++) {
-		if (rdmsr_safe(msrs_to_save_all[i], &dummy[0], &dummy[1]) < 0)
+		msr_index = msrs_to_save_all[i];
+
+		if (rdmsr_safe(msr_index, &dummy[0], &dummy[1]) < 0)
 			continue;
 
 		/*
 		 * Even MSRs that are valid in the host may not be exposed
 		 * to the guests in some cases.
 		 */
-		switch (msrs_to_save_all[i]) {
+		switch (msr_index) {
 		case MSR_IA32_BNDCFGS:
 			if (!kvm_mpx_supported())
 				continue;
@@ -5262,17 +5264,17 @@ static void kvm_init_msr_list(void)
 			break;
 		case MSR_IA32_RTIT_ADDR0_A ... MSR_IA32_RTIT_ADDR3_B:
 			if (!kvm_x86_ops->pt_supported() ||
-				msrs_to_save_all[i] - MSR_IA32_RTIT_ADDR0_A >=
+				msr_index - MSR_IA32_RTIT_ADDR0_A >=
 				intel_pt_validate_hw_cap(PT_CAP_num_address_ranges) * 2)
 				continue;
 			break;
 		case MSR_ARCH_PERFMON_PERFCTR0 ... MSR_ARCH_PERFMON_PERFCTR0 + 17:
-			if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_PERFCTR0 >=
+			if (msr_index - MSR_ARCH_PERFMON_PERFCTR0 >=
 			    min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp))
 				continue;
 			break;
 		case MSR_ARCH_PERFMON_EVENTSEL0 ... MSR_ARCH_PERFMON_EVENTSEL0 + 17:
-			if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_EVENTSEL0 >=
+			if (msr_index - MSR_ARCH_PERFMON_EVENTSEL0 >=
 			    min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp))
 				continue;
 			break;
@@ -5280,14 +5282,16 @@ static void kvm_init_msr_list(void)
 			break;
 		}
 
-		msrs_to_save[num_msrs_to_save++] = msrs_to_save_all[i];
+		msrs_to_save[num_msrs_to_save++] = msr_index;
 	}
 
 	for (i = 0; i < ARRAY_SIZE(emulated_msrs_all); i++) {
-		if (!kvm_x86_ops->has_emulated_msr(emulated_msrs_all[i]))
+		msr_index = emulated_msrs_all[i];
+
+		if (!kvm_x86_ops->has_emulated_msr(msr_index))
 			continue;
 
-		emulated_msrs[num_emulated_msrs++] = emulated_msrs_all[i];
+		emulated_msrs[num_emulated_msrs++] = msr_index;
 	}
 
 	for (i = 0; i < ARRAY_SIZE(msr_based_features_all); i++) {
-- 
2.24.1

