linux-kernel - Re: [PATCH V5] perf: Add PERF_SAMPLE_PHYS

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Message-ID: <20170822170736.GI32112@worktop.programming.kicks-ass.net>
Date:   Tue, 22 Aug 2017 19:07:36 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...el.com
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org, acme@...nel.org,
        jolsa@...hat.com, tglx@...utronix.de, eranian@...gle.com,
        ak@...ux.intel.com
Subject: Re: [PATCH V5] perf: Add PERF_SAMPLE_PHYS_ADDR

On Thu, Aug 17, 2017 at 02:17:23PM -0400, kan.liang@...el.com wrote:
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index a322fed..f0e8d9c 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -1065,6 +1065,35 @@ static inline u64 intel_hsw_transaction(struct pebs_record_skl *pebs)
>  	return txn;
>  }
>  
> +static u64 dla_to_phys(u64 dla)
> +{
> +	u64 phys_addr = 0;
> +	struct page *p = NULL;
> +
> +	if (dla >= TASK_SIZE) {
> +		/* If it's vmalloc()d memory, leave phys_addr as 0 */
> +		if (virt_addr_valid(dla) &&
> +		    !(dla >= VMALLOC_START && dla < VMALLOC_END))
> +			phys_addr = (u64)virt_to_phys((void *)(uintptr_t)dla);
> +	} else {
> +		/*
> +		 * Walking the pages tables for user address.
> +		 * Interrupts are disabled, so it prevents any tear down
> +		 * of the page tables.
> +		 * Try IRQ-safe __get_user_pages_fast first.
> +		 * If failed, leave phys_addr as 0.
> +		 */
> +		if ((current->mm != NULL) &&
> +		    (__get_user_pages_fast(dla, 1, 0, &p) == 1))
> +			phys_addr = page_to_phys(p) + dla % PAGE_SIZE;
> +
> +		if (p)
> +			put_page(p);
> +	}
> +
> +	return phys_addr;
> +}

Is this in any way x86 specific? AFAICT this should work in generic code
as long as data->addr is provided.

>  static void setup_pebs_sample_data(struct perf_event *event,
>  				   struct pt_regs *iregs, void *__pebs,
>  				   struct perf_sample_data *data,
> @@ -1179,6 +1208,9 @@ static void setup_pebs_sample_data(struct perf_event *event,
>  	    x86_pmu.intel_cap.pebs_format >= 1)
>  		data->addr = pebs->dla;
>  
> +	if ((sample_type & PERF_SAMPLE_PHYS_ADDR) && (data->addr != 0))
> +		data->phys_addr = dla_to_phys(data->addr);
> +
>  	if (x86_pmu.intel_cap.pebs_format >= 2) {
>  		/* Only set the TSX weight when no memory weight. */
>  		if ((sample_type & PERF_SAMPLE_WEIGHT) && !fll)