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

Sean Christopherson
2020-01-29T23:48:42Z

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