On Thu, Jul 22, 2021 at 01:41:41PM +0800, Zhu Lingshan wrote:
> The guest Precise Event Based Sampling (PEBS) feature can provide an
> architectural state of the instruction executed after the guest instruction
> that exactly caused the event. It needs new hardware facility only available
> on Intel Ice Lake Server platforms. This patch set enables the basic PEBS
> feature for KVM guests on ICX.
>
> We can use PEBS feature on the Linux guest like native:
>
> # echo 0 > /proc/sys/kernel/watchdog (on the host)
> # perf record -e instructions:ppp ./br_instr a
> # perf record -c 100000 -e instructions:pp ./br_instr a
Why does the host need to disable the watchdog? IIRC ICL has multiple
PEBS capable counters. Also, I think the watchdog ends up on a fixed
counter by default anyway.
> Like Xu (17):
> perf/core: Use static_call to optimize perf_guest_info_callbacks
> perf/x86/intel: Add EPT-Friendly PEBS for Ice Lake Server
> perf/x86/intel: Handle guest PEBS overflow PMI for KVM guest
> perf/x86/core: Pass "struct kvm_pmu *" to determine the guest values
> KVM: x86/pmu: Set MSR_IA32_MISC_ENABLE_EMON bit when vPMU is enabled
> KVM: x86/pmu: Introduce the ctrl_mask value for fixed counter
> KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS
> KVM: x86/pmu: Reprogram PEBS event to emulate guest PEBS counter
> KVM: x86/pmu: Adjust precise_ip to emulate Ice Lake guest PDIR counter
> KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to support guest DS
> KVM: x86/pmu: Add PEBS_DATA_CFG MSR emulation to support adaptive PEBS
> KVM: x86: Set PEBS_UNAVAIL in IA32_MISC_ENABLE when PEBS is enabled
> KVM: x86/pmu: Move pmc_speculative_in_use() to arch/x86/kvm/pmu.h
> KVM: x86/pmu: Disable guest PEBS temporarily in two rare situations
> KVM: x86/pmu: Add kvm_pmu_cap to optimize perf_get_x86_pmu_capability
> KVM: x86/cpuid: Refactor host/guest CPU model consistency check
> KVM: x86/pmu: Expose CPUIDs feature bits PDCM, DS, DTES64
>
> Peter Zijlstra (Intel) (1):
> x86/perf/core: Add pebs_capable to store valid PEBS_COUNTER_MASK value
Looks good:
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
How do we want to route this, all through the KVM tree?
One little nit I had; would something like the below (on top perhaps)
make the code easier to read?
---
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3921,9 +3921,12 @@ static struct perf_guest_switch_msr *int
struct kvm_pmu *kvm_pmu = (struct kvm_pmu *)data;
u64 intel_ctrl = hybrid(cpuc->pmu, intel_ctrl);
u64 pebs_mask = cpuc->pebs_enabled & x86_pmu.pebs_capable;
+ int global_ctrl, pebs_enable;
*nr = 0;
- arr[(*nr)++] = (struct perf_guest_switch_msr){
+
+ global_ctrl = (*nr)++;
+ arr[global_ctrl] = (struct perf_guest_switch_msr){
.msr = MSR_CORE_PERF_GLOBAL_CTRL,
.host = intel_ctrl & ~cpuc->intel_ctrl_guest_mask,
.guest = intel_ctrl & (~cpuc->intel_ctrl_host_mask | ~pebs_mask),
@@ -3966,23 +3969,23 @@ static struct perf_guest_switch_msr *int
};
}
- arr[*nr] = (struct perf_guest_switch_msr){
+ pebs_enable = (*nr)++;
+ arr[pebs_enable] = (struct perf_guest_switch_msr){
.msr = MSR_IA32_PEBS_ENABLE,
.host = cpuc->pebs_enabled & ~cpuc->intel_ctrl_guest_mask,
.guest = pebs_mask & ~cpuc->intel_ctrl_host_mask,
};
- if (arr[*nr].host) {
+ if (arr[pebs_enable].host) {
/* Disable guest PEBS if host PEBS is enabled. */
- arr[*nr].guest = 0;
+ arr[pebs_enable].guest = 0;
} else {
/* Disable guest PEBS for cross-mapped PEBS counters. */
- arr[*nr].guest &= ~kvm_pmu->host_cross_mapped_mask;
+ arr[pebs_enable].guest &= ~kvm_pmu->host_cross_mapped_mask;
/* Set hw GLOBAL_CTRL bits for PEBS counter when it runs for guest */
- arr[0].guest |= arr[*nr].guest;
+ arr[global_ctrl].guest |= arr[pebs_enable].guest;
}
- ++(*nr);
return arr;
}
