RE: [PATCH V3] perf: Add PERF_SAMPLE_PHYS_ADDR

From: Liang, Kan
Date: Thu Aug 17 2017 - 09:42:31 EST

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> On Wed, Aug 9, 2017 at 1:42 PM, <kan.liang@xxxxxxxxx> wrote:
> > From: Kan Liang <kan.liang@xxxxxxxxx>
> >
> > 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.
> > However, perf doesn't collect physical address information in sampling.
> >
> > The load latency/DLA information in PEBS can be used to calculate the
> > physical address.
> > For kernel direct mapping addresses, virt_to_phys is used to convert the
> > virtual addresses from DLA 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.
> > For security, the physical address can only be exposed to root or
> > privileged user.
> > A new sample type PERF_SAMPLE_PHYS_ADDR is introduced to expose the
> > physical addresses.
> >
> > Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
>
> This is a useful feature that I would like to use for some of the
> analysis we would like to do.
> Please apply.
> I am assuming you have the support in perf record/report?
>

Yes, the previous version includes both kernel and user space code.
https://lkml.org/lkml/2016/1/7/608
V3 only includes the kernel version.
Once it is accepted, I will send out the rest of patches for review.

> > ---
> >
> > The V2 version can be found here.
> > https://patchwork.kernel.org/patch/7979771/
> >
> > Changes since V2
> > - Only the kernel patch
> > - Add example in changelog
> > - Include a perf_paranoid_kernel() test (PeterZ)
> > - Fix minor complier warning
> >
> > arch/x86/events/intel/ds.c | 24 ++++++++++++++++++++++++
> > arch/x86/events/perf_event.h | 2 +-
> > include/linux/perf_event.h | 3 +++
> > include/uapi/linux/perf_event.h | 4 +++-
> > kernel/events/core.c | 12 ++++++++++++
> > 5 files changed, 43 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> > index a322fed..712c86b 100644
> > --- a/arch/x86/events/intel/ds.c
> > +++ b/arch/x86/events/intel/ds.c
> > @@ -1083,6 +1083,7 @@ static void setup_pebs_sample_data(struct
> perf_event *event,
> > u64 sample_type;
> > int fll, fst, dsrc;
> > int fl = event->hw.flags;
> > + struct page *p = NULL;
> >
> > if (pebs == NULL)
> > return;
> > @@ -1179,6 +1180,29 @@ 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)) {
> > + if (data->addr >= TASK_SIZE) {
> > + /* If it's vmalloc()d memory, leave phys_addr as 0 */
> > + if (virt_addr_valid(data->addr) &&
> > + !(data->addr >= VMALLOC_START && data->addr <
> VMALLOC_END))
> > + data->phys_addr = (u64)virt_to_phys((void
> *)(uintptr_t)data->addr);
> > + } 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(data->addr, 1, 0, &p) == 1))
> > + data->phys_addr = page_to_phys(p) + data->addr %
> PAGE_SIZE;
> > +
> > + if (p)
> > + put_page(p);
> > + }
> > + }
> > +
> This would be cleaner in a separate function in my opinion.

Will change it in next version.

>
> > if (x86_pmu.intel_cap.pebs_format >= 2) {
> > /* Only set the TSX weight when no memory weight. */
> > if ((sample_type & PERF_SAMPLE_WEIGHT) && !fll)
> > 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 a3b873f..6783c69 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 */
> > @@ -964,6 +966,7 @@ static inline void perf_sample_data_init(struct
> perf_sample_data *data,
> > data->weight = 0;
> > data->data_src.val = PERF_MEM_NA;
> > data->txn = 0;
> > + data->phys_addr = 0;
> > }
> >
> > extern void perf_output_sample(struct perf_output_handle *handle,
> > 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 426c2ff..07d4a74 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;
> > }
> >
> > @@ -5952,6 +5955,9 @@ void perf_output_sample(struct
> perf_output_handle *handle,
> > if (sample_type & PERF_SAMPLE_DATA_SRC)
> > perf_output_put(handle, data->data_src.val);
> >
> > + if (sample_type & PERF_SAMPLE_PHYS_ADDR)
> > + perf_output_put(handle, data->phys_addr);
> > +
>
> I think this is misplaced. You need to output in the order in which
> you describe the record in the header file.
> You have: DATA_SRC, SAMPLE_TRANSACTION, REGS_INTR, PHYS_ADDR. That
> means you need to
> output in that order. Otherwise your PHYS_ADDR may be interpreted as a
> SAMPLE_TRANSACTION in case it is active.
> At least this is my understanding of the ABI here.
>

Will change it in next version.

Thanks,
Kan

>
> > if (sample_type & PERF_SAMPLE_TRANSACTION)
> > perf_output_put(handle, data->txn);
> >
> > @@ -9852,6 +9858,12 @@ 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;
> >
> > --
> > 2.4.3
> >

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Previous message: Jiri Kosina: "Re: [linuxwifi] x86/thermal: AB-BA dependency between mvm->mutex and tz->lock"
In reply to: Stephane Eranian: "Re: [PATCH V3] perf: Add PERF_SAMPLE_PHYS_ADDR"
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