Date:   Tue, 29 Aug 2017 17:05:15 +0530
From:   Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
To:     kan.liang@...el.com, peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     acme@...nel.org, jolsa@...hat.com, tglx@...utronix.de,
        eranian@...gle.com, ak@...ux.intel.com, mpe@...erman.id.au
Subject: Re: [PATCH V8] perf: Add PERF_SAMPLE_PHYS_ADDR



On Tuesday 29 August 2017 06:22 AM, kan.liang@...el.com wrote:
> From: Kan Liang <kan.liang@...el.com>
>
> For understanding how the workload maps to memory channels and hardware
> behavior, it's very important to collect address maps with physical
> addresses. For example, 3D XPoint access can only be found by filtering
> the physical address.
>
> Add a new sample type for physical address.
>
> perf already has a facility to collect data virtual address. This patch
> introduces a function to convert the virtual address to physical address.
> The function is quite generic and can be extended to any architecture as
> long as a virtual address is provided.
>   - For kernel direct mapping addresses, virt_to_phys is used to convert
>     the virtual addresses to physical address.
>   - For user virtual addresses, __get_user_pages_fast is used to walk the
>     pages tables for user physical address.
>   - This does not work for vmalloc addresses right now. These are not
>     resolved, but code to do that could be added.
>
> The new sample type requires collecting the virtual address. The
> virtual address will not be output unless SAMPLE_ADDR is applied.
>
> For security, the physical address can only be exposed to root or
> privileged user.

Tested-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>

>
> Signed-off-by: Kan Liang <kan.liang@...el.com>
> ---
>
> This patch is kernel patch.
> The user space patch can be found here.
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.spinics.net_lists_kernel_msg2587093.html&d=DwIBaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=3f2W2m24mqGnx1C8qDsVjM_Sd89MwbaDB37IJVL-h7w&m=bL7qsJKf8aRpvBVr07ODZxoQhPgxffpGFgN9A4iyACw&s=R1OMYJt1szqNhPZu8QQDDRCnQgHZiQzcCPzofF6FIF8&e=
>
> Changes since V7
>   - Fix virt_addr_valid compile warning for MIPS architecture (LKP)
>
>   arch/powerpc/perf/core-book3s.c |  3 ++-
>   arch/x86/events/intel/ds.c      |  2 +-
>   arch/x86/events/perf_event.h    |  2 +-
>   include/linux/perf_event.h      |  2 ++
>   include/uapi/linux/perf_event.h |  4 +++-
>   kernel/events/core.c            | 47 +++++++++++++++++++++++++++++++++++++++++
>   6 files changed, 56 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index 6c2d416..2e3eb74 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -2039,7 +2039,8 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
>   
>   		perf_sample_data_init(&data, ~0ULL, event->hw.last_period);
>   
> -		if (event->attr.sample_type & PERF_SAMPLE_ADDR)
> +		if (event->attr.sample_type &
> +		    (PERF_SAMPLE_ADDR | PERF_SAMPLE_PHYS_ADDR))
>   			perf_get_data_addr(regs, &data.addr);
>   
>   		if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index a322fed..0516f78 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -1175,7 +1175,7 @@ static void setup_pebs_sample_data(struct perf_event *event,
>   	else
>   		regs->flags &= ~PERF_EFLAGS_EXACT;
>   
> -	if ((sample_type & PERF_SAMPLE_ADDR) &&
> +	if ((sample_type & (PERF_SAMPLE_ADDR | PERF_SAMPLE_PHYS_ADDR)) &&
>   	    x86_pmu.intel_cap.pebs_format >= 1)
>   		data->addr = pebs->dla;
>   
> diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
> index 476aec3..65bb91e 100644
> --- a/arch/x86/events/perf_event.h
> +++ b/arch/x86/events/perf_event.h
> @@ -91,7 +91,7 @@ struct amd_nb {
>   	(PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_ADDR | \
>   	PERF_SAMPLE_ID | PERF_SAMPLE_CPU | PERF_SAMPLE_STREAM_ID | \
>   	PERF_SAMPLE_DATA_SRC | PERF_SAMPLE_IDENTIFIER | \
> -	PERF_SAMPLE_TRANSACTION)
> +	PERF_SAMPLE_TRANSACTION | PERF_SAMPLE_PHYS_ADDR)
>   
>   /*
>    * A debug store configuration.
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index b14095b..74fb87e 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -944,6 +944,8 @@ struct perf_sample_data {
>   
>   	struct perf_regs		regs_intr;
>   	u64				stack_user_size;
> +
> +	u64				phys_addr;
>   } ____cacheline_aligned;
>   
>   /* default value for data source */
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 642db5f..cbea02f 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -139,8 +139,9 @@ enum perf_event_sample_format {
>   	PERF_SAMPLE_IDENTIFIER			= 1U << 16,
>   	PERF_SAMPLE_TRANSACTION			= 1U << 17,
>   	PERF_SAMPLE_REGS_INTR			= 1U << 18,
> +	PERF_SAMPLE_PHYS_ADDR			= 1U << 19,
>   
> -	PERF_SAMPLE_MAX = 1U << 19,		/* non-ABI */
> +	PERF_SAMPLE_MAX = 1U << 20,		/* non-ABI */
>   };
>   
>   /*
> @@ -814,6 +815,7 @@ enum perf_event_type {
>   	 *	{ u64			transaction; } && PERF_SAMPLE_TRANSACTION
>   	 *	{ u64			abi; # enum perf_sample_regs_abi
>   	 *	  u64			regs[weight(mask)]; } && PERF_SAMPLE_REGS_INTR
> +	 *	{ u64			phys_addr;} && PERF_SAMPLE_PHYS_ADDR
>   	 * };
>   	 */
>   	PERF_RECORD_SAMPLE			= 9,
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index d704e23..e8d5c5d 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1570,6 +1570,9 @@ static void __perf_event_header_size(struct perf_event *event, u64 sample_type)
>   	if (sample_type & PERF_SAMPLE_TRANSACTION)
>   		size += sizeof(data->txn);
>   
> +	if (sample_type & PERF_SAMPLE_PHYS_ADDR)
> +		size += sizeof(data->phys_addr);
> +
>   	event->header_size = size;
>   }
>   
> @@ -6012,6 +6015,9 @@ void perf_output_sample(struct perf_output_handle *handle,
>   		}
>   	}
>   
> +	if (sample_type & PERF_SAMPLE_PHYS_ADDR)
> +		perf_output_put(handle, data->phys_addr);
> +
>   	if (!event->attr.watermark) {
>   		int wakeup_events = event->attr.wakeup_events;
>   
> @@ -6027,6 +6033,38 @@ void perf_output_sample(struct perf_output_handle *handle,
>   	}
>   }
>   
> +static u64 perf_virt_to_phys(u64 virt)
> +{
> +	u64 phys_addr = 0;
> +	struct page *p = NULL;
> +
> +	if (!virt)
> +		return 0;
> +
> +	if (virt >= TASK_SIZE) {
> +		/* If it's vmalloc()d memory, leave phys_addr as 0 */
> +		if (virt_addr_valid((void *)(uintptr_t)virt) &&
> +		    !(virt >= VMALLOC_START && virt < VMALLOC_END))
> +			phys_addr = (u64)virt_to_phys((void *)(uintptr_t)virt);
> +	} 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(virt, 1, 0, &p) == 1))
> +			phys_addr = page_to_phys(p) + virt % PAGE_SIZE;
> +
> +		if (p)
> +			put_page(p);
> +	}
> +
> +	return phys_addr;
> +}
> +
>   void perf_prepare_sample(struct perf_event_header *header,
>   			 struct perf_sample_data *data,
>   			 struct perf_event *event,
> @@ -6145,6 +6183,9 @@ void perf_prepare_sample(struct perf_event_header *header,
>   
>   		header->size += size;
>   	}
> +
> +	if (sample_type & PERF_SAMPLE_PHYS_ADDR)
> +		data->phys_addr = perf_virt_to_phys(data->addr);
>   }
>   
>   static void __always_inline
> @@ -9892,6 +9933,12 @@ SYSCALL_DEFINE5(perf_event_open,
>   			return -EINVAL;
>   	}
>   
> +	/* Only privileged users can get kernel addresses */
> +	if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) &&
> +	    perf_paranoid_kernel() &&
> +	    !capable(CAP_SYS_ADMIN))
> +		return -EACCES;
> +
>   	if (!attr.sample_max_stack)
>   		attr.sample_max_stack = sysctl_perf_event_max_stack;
>   

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