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    SubjectRe: [PATCH V6] perf: Add PERF_SAMPLE_PHYS_ADDR
    On Wed, Aug 23, 2017 at 7:39 AM, Peter Zijlstra <peterz@infradead.org> wrote:
    > On Wed, Aug 23, 2017 at 04:33:08PM +0200, Peter Zijlstra wrote:
    >> > @@ -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);
    >>
    >> Only problem with this now is that it requires SAMPLE_ADDR to also be
    >> set in order to obtain data->addr.
    >>
    >> Either fix all to set data->attr for (SAMPLE_ADDR || SAMPLE_PHYS_ADDR)
    >> or mandate SAMPLE_ADDR when SAMPLE_PHYS_ADDR.
    >
    > I think the former suggestion is better, as it allows for smaller
    > samples.

    Agreed. I may only care about physical addresses, so SAMPLE_PHYS_ADDR
    should suffice from the user.
    The kernel must save the virtual address in data->addr, and then convert it.

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