Re: [PATCH V1 2/4] KVM: x86/vPMU: Convert pmu.c code into Intel specific code

["Radim Krčmář" <rkrcmar@redhat.com>]

2014-10-31 12:05-0400, Wei Huang:
> This patch converts existing pmu.c into Intel specific code and hooks
> up with the PMU interface using the following steps:
> 
> - Convert pmu.c to pmu_intel.c; All public PMU functions are renamed
>   and hooked up with the newly defined intel_pmu_ops.
> - Create a corresponding pmu_amd.c file with empty functions for AMD
>   arch.
> - The PMU function pointer, kvm_pmu_ops, is initialized by calling
>   kvm_x86_ops->get_pmu_ops().
> - To reduce the code size, Intel and AMD modules are now generated
>   from their corrponding arch and PMU files; In the meanwhile, due
>   to this arrangement several, functions are exposed as public ones
>   to allow calling from PMU code.

(Patch would have been easier to review as two patches, where the first
 one just renames pmu to pmu_intel and the second one does the split.)

> Signed-off-by: Wei Huang <wei@redhat.com>
> ---

---
The rest is an idea for consideration ...
Please consider everything from now to be in parentheses
= ignore you are not enjoying shuffling code around.

> +
> +static unsigned find_arch_event(struct kvm_pmu *pmu, u8 event_select,
> +		u8 unit_mask)

The prototype could be exteded with
  struct kvm_event_hw_type_mapping, size_t nr_events
and reused for AMD as well.

> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(intel_arch_events); i++)
> +		if (intel_arch_events[i].eventsel == event_select
> +				&& intel_arch_events[i].unit_mask == unit_mask
> +				&& (pmu->available_event_types & (1 << i)))

pmu->available_event_types would be -1 on AMD.

> +			break;
> +
> +	if (i == ARRAY_SIZE(intel_arch_events))
> +		return PERF_COUNT_HW_MAX;
> +
> +	return intel_arch_events[i].event_type;
> +}

> +static void reprogram_counter(struct kvm_pmc *pmc, u32 type,
> +		unsigned config, bool exclude_user, bool exclude_kernel,
> +		bool intr, bool in_tx, bool in_tx_cp)

This function could drop 'bool in_tx' and 'bool in_tx_cp', because it
already accepts config, so these flags can already be included there.
It has only one caller that uses them anyway.

> +{
> +	struct perf_event *event;
> +	struct perf_event_attr attr = {
> +		.type = type,
> +		.size = sizeof(attr),
> +		.pinned = true,
> +		.exclude_idle = true,
> +		.exclude_host = 1,
> +		.exclude_user = exclude_user,
> +		.exclude_kernel = exclude_kernel,
> +		.config = config,
> +	};
> +	if (in_tx)
> +		attr.config |= HSW_IN_TX;
> +	if (in_tx_cp)
> +		attr.config |= HSW_IN_TX_CHECKPOINTED;

And after dropping this, it is identical to AMD.

> +
> +	attr.sample_period = (-pmc->counter) & pmc_bitmask(pmc);
> +
> +	event = perf_event_create_kernel_counter(&attr, -1, current,
> +						 intr ? kvm_perf_overflow_intr :
> +						 kvm_perf_overflow, pmc);
> +	if (IS_ERR(event)) {
> +		printk_once("kvm: pmu event creation failed %ld\n",
> +				PTR_ERR(event));
> +		return;
> +	}
> +
> +	pmc->perf_event = event;
> +	clear_bit(pmc->idx, (unsigned long*)&pmc->vcpu->arch.pmu.reprogram_pmi);
> +}
> +
> +static void reprogram_gp_counter(struct kvm_pmc *pmc, u64 eventsel)
> +{

Because the two functions that this one uses have been merged, we could
propagate the changes and reuse this one with AMD as well.

> +	unsigned config, type = PERF_TYPE_RAW;
> +	u8 event_select, unit_mask;
> +
> +	if (eventsel & ARCH_PERFMON_EVENTSEL_PIN_CONTROL)
> +		printk_once("kvm pmu: pin control bit is ignored\n");
> +
> +	pmc->eventsel = eventsel;
> +
> +	stop_counter(pmc);
> +
> +	if (!(eventsel & ARCH_PERFMON_EVENTSEL_ENABLE) || !pmc_enabled(pmc))
> +		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))) {
> +		config = find_arch_event(&pmc->vcpu->arch.pmu, event_select,
> +				unit_mask);
> +		if (config != PERF_COUNT_HW_MAX)
> +			type = PERF_TYPE_HARDWARE;
> +	}
> +
> +	if (type == PERF_TYPE_RAW)
> +		config = eventsel & X86_RAW_EVENT_MASK;
> +
> +	reprogram_counter(pmc, type, config,
> +			!(eventsel & ARCH_PERFMON_EVENTSEL_USR),
> +			!(eventsel & ARCH_PERFMON_EVENTSEL_OS),
> +			eventsel & ARCH_PERFMON_EVENTSEL_INT,
> +			(eventsel & HSW_IN_TX),
> +			(eventsel & HSW_IN_TX_CHECKPOINTED));
> +}