perf: Add PERF_SAMPLE_PHYS_ADDR

From: Kan Liang <[email protected]>

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.

Signed-off-by Kan Liang <[email protected]>

---

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(-)

arch/powerpc/perf/core-book3s.c +2 -1

index 6c2d416..2e3eb74 100644
@@ -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) {

arch/x86/events/intel/ds.c +1 -1

index a322fed..0516f78 100644
@@ -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;
 

arch/x86/events/perf_event.h +1 -1

index 476aec3..65bb91e 100644
@@ -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.

include/linux/perf_event.h +2 -0

index b14095b..74fb87e 100644
@@ -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 */

include/uapi/linux/perf_event.h +3 -1

index 642db5f..cbea02f 100644
@@ -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,

kernel/events/core.c +47 -0

index d704e23..e8d5c5d 100644
@@ -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;
 

Quoted 20 lines · On Tuesday 29 August 2017 06:22 AM, [email protected] wrote:

From: Kan Liang <[email protected]>

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.

Quoted 5 lines

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 <[email protected]>

Quoted 23 lines · On Tuesday 29 August 2017 06:22 AM, [email protected] wrote:

Quoted 20 lines

From: Kan Liang <[email protected]>

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.

Quoted 7 lines

Quoted 5 lines

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 <[email protected]>

Thanks maddy!

Em Tue, Aug 29, 2017 at 01:45:53PM +0200, Peter Zijlstra escreveu:
On Tue, Aug 29, 2017 at 05:05:15PM +0530, Madhavan Srinivasan wrote:

On Tuesday 29 August 2017 06:22 AM, [email protected] wrote:
From: Kan Liang <[email protected]>

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 <[email protected]>

You mean you tested this together with Kan's v2 perf tools patches? If that is so I'll add this tested-by to those patches, ok? Arnaldo,

No. Kernel side patch showed the link for the v1 of the perf tool side patchset (5 patch series) and I used that to test.

Quoted 4 lines

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_iaSHv JObTbx-siA1ZOg&r=3f2W2m24mqGnx1C8qDsVjM_Sd89MwbaDB37IJVL- h7w&m=bL7qsJKf8aRpvBVr07ODZxoQhPgxffpGFgN9A4iyACw&s=R1OMYJt1sz qNhPZu8QQDDRCnQgHZiQzcCPzofF6FIF8&e=

Maddy

Thanks maddy!