[PATCH v4 02/12] KVM: VMX: Refactor intel_pmu_set_msr() to align with other set_msr() helpers

Like Xu
2023-02-14T05:08:32Z

From: Sean Christopherson <seanjc@google.com>

Invert the flows in intel_pmu_set_msr()'s case statements so that they
follow the kernel's preferred style of:

if (<not valid>)
return <error>

<commit change>
return <success>

which is also the style used by every other set_msr() helper (except
AMD's PMU variant, which doesn't use a switch statement).

Opportunstically move the "val == current" checks below the validity
checks. Except for the one-off case for MSR_P6_EVNTSEL2, the reserved
bit checks are extremely cheap, and the guest is unlikely to frequently
write the current value, i.e. avoiding the reserved bit checks doesn't
add much (any?) value.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/pmu_intel.c | 81 +++++++++++++++++++-----------------
1 file changed, 42 insertions(+), 39 deletions(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index e8a3be0b9df9..6a2f8b4ed061 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -402,44 +402,43 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)

switch (msr) {
case MSR_CORE_PERF_FIXED_CTR_CTRL:
- if (pmu->fixed_ctr_ctrl == data)
- return 0;
- if (!(data & pmu->fixed_ctr_ctrl_mask)) {
+ if (data & pmu->fixed_ctr_ctrl_mask)
+ return 1;
+
+ if (pmu->fixed_ctr_ctrl != data)
reprogram_fixed_counters(pmu, data);
- return 0;
- }
break;
case MSR_CORE_PERF_GLOBAL_STATUS:
- if (msr_info->host_initiated) {
- pmu->global_status = data;
- return 0;
- }
- break; /* RO MSR */
+ if (!msr_info->host_initiated)
+ return 1; /* RO MSR */
+
+ pmu->global_status = data;
+ break;
case MSR_CORE_PERF_GLOBAL_CTRL:
- if (pmu->global_ctrl == data)
- return 0;
- if (kvm_valid_perf_global_ctrl(pmu, data)) {
+ if (!kvm_valid_perf_global_ctrl(pmu, data))
+ return 1;
+
+ if (pmu->global_ctrl != data) {
diff = pmu->global_ctrl ^ data;
pmu->global_ctrl = data;
reprogram_counters(pmu, diff);
- return 0;
}
break;
case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
- if (!(data & pmu->global_ovf_ctrl_mask)) {
- if (!msr_info->host_initiated)
- pmu->global_status &= ~data;
- return 0;
- }
+ if (data & pmu->global_ovf_ctrl_mask)
+ return 1;
+
+ if (!msr_info->host_initiated)
+ pmu->global_status &= ~data;
break;
case MSR_IA32_PEBS_ENABLE:
- if (pmu->pebs_enable == data)
- return 0;
- if (!(data & pmu->pebs_enable_mask)) {
+ if (data & pmu->pebs_enable_mask)
+ return 1;
+
+ if (pmu->pebs_enable != data) {
diff = pmu->pebs_enable ^ data;
pmu->pebs_enable = data;
reprogram_counters(pmu, diff);
- return 0;
}
break;
case MSR_IA32_DS_AREA:
@@ -447,15 +446,14 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 1;
if (is_noncanonical_address(data, vcpu))
return 1;
+
pmu->ds_area = data;
- return 0;
+ break;
case MSR_PEBS_DATA_CFG:
- if (pmu->pebs_data_cfg == data)
- return 0;
- if (!(data & pmu->pebs_data_cfg_mask)) {
- pmu->pebs_data_cfg = data;
- return 0;
- }
+ if (data & pmu->pebs_data_cfg_mask)
+ return 1;
+
+ pmu->pebs_data_cfg = data;
break;
default:
if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
@@ -463,33 +461,38 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if ((msr & MSR_PMC_FULL_WIDTH_BIT) &&
(data & ~pmu->counter_bitmask[KVM_PMC_GP]))
return 1;
+
if (!msr_info->host_initiated &&
!(msr & MSR_PMC_FULL_WIDTH_BIT))
data = (s64)(s32)data;
pmc->counter += data - pmc_read_counter(pmc);
pmc_update_sample_period(pmc);
- return 0;
+ break;
} else if ((pmc = get_fixed_pmc(pmu, msr))) {
pmc->counter += data - pmc_read_counter(pmc);
pmc_update_sample_period(pmc);
- return 0;
+ break;
} else if ((pmc = get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0))) {
- if (data == pmc->eventsel)
- return 0;
reserved_bits = pmu->reserved_bits;
if ((pmc->idx == 2) &&
(pmu->raw_event_mask & HSW_IN_TX_CHECKPOINTED))
reserved_bits ^= HSW_IN_TX_CHECKPOINTED;
- if (!(data & reserved_bits)) {
+ if (data & reserved_bits)
+ return 1;
+
+ if (data != pmc->eventsel) {
pmc->eventsel = data;
kvm_pmu_request_counter_reprogam(pmc);
- return 0;
}
- } else if (intel_pmu_handle_lbr_msrs_access(vcpu, msr_info, false))
- return 0;
+ break;
+ } else if (intel_pmu_handle_lbr_msrs_access(vcpu, msr_info, false)) {
+ break;
+ }
+ /* Not a known PMU MSR. */
+ return 1;
}

- return 1;
+ return 0;
}

static void setup_fixed_pmc_eventsel(struct kvm_pmu *pmu)
--
2.39.1