On Mon, Nov 29, 2021 at 11:42 PM Like Xu <like.xu.linux@xxxxxxxxx> wrote:
>
> From: Like Xu <likexu@xxxxxxxxxxx>
>
> The find_arch_event() returns a "unsigned int" value,
> which is used by the pmc_reprogram_counter() to
> program a PERF_TYPE_HARDWARE type perf_event.
>
> The returned value is actually the kernel defined generic
Typo: generic.
> perf_hw_id, let's rename it to pmc_perf_hw_id() with simpler
> incoming parameters for better self-explanation.
>
> Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
> ---
> arch/x86/kvm/pmu.c | 8 +-------
> arch/x86/kvm/pmu.h | 3 +--
> arch/x86/kvm/svm/pmu.c | 8 ++++----
> arch/x86/kvm/vmx/pmu_intel.c | 9 +++++----
> 4 files changed, 11 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
> index 09873f6488f7..3b3ccf5b1106 100644
> --- a/arch/x86/kvm/pmu.c
> +++ b/arch/x86/kvm/pmu.c
> @@ -174,7 +174,6 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc)
> void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel)
> {
> unsigned config, type = PERF_TYPE_RAW;
> - u8 event_select, unit_mask;
> struct kvm *kvm = pmc->vcpu->kvm;
> struct kvm_pmu_event_filter *filter;
> int i;
> @@ -206,17 +205,12 @@ void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel)
> if (!allow_event)
> return;
>
> - event_select = eventsel & ARCH_PERFMON_EVENTSEL_EVENT;
> - unit_mask = (eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8;
> -
> if (!(eventsel & (ARCH_PERFMON_EVENTSEL_EDGE |
> ARCH_PERFMON_EVENTSEL_INV |
> ARCH_PERFMON_EVENTSEL_CMASK |
> HSW_IN_TX |
> HSW_IN_TX_CHECKPOINTED))) {
The mechanics of the change look fine, but I do have some questions,
for my own understanding.
Why don't we just use PERF_TYPE_RAW for guest counters all of the
time? What is the advantage of matching entries in a table so that we
can use PERF_TYPE_HARDWARE?
Why do the HSW_IN_TX* bits result in bypassing this clause, when these
bits are extracted as arguments to pmc_reprogram_counter below?
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
