On Mon, Jan 16, 2017 at 01:23:34AM -0600, Suravee Suthikulpanit wrote: > From: Suravee Suthikulpanit <[email protected]> > > In, perf_iommu_start(), we need to check the return value from > amd_iommu_set_reg(). In case of failure, we should not enable the PMU. > > Also, in perf_iommu_read(), we need to check the return value from > amd_iommu_get_reg() before using the value. > > Cc: Peter Zijlstra <[email protected]> > Cc: Borislav Petkov <[email protected]> > Cc: Joerg Roedel <[email protected]> > Signed-off-by: Suravee Suthikulpanit <[email protected]> > --- > arch/x86/events/amd/iommu.c | 19 +++++++++++-------- > 1 file changed, 11 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/events/amd/iommu.c b/arch/x86/events/amd/iommu.c > index 200d2e8..cc7bea4 100644 > --- a/arch/x86/events/amd/iommu.c > +++ b/arch/x86/events/amd/iommu.c > @@ -284,6 +284,7 @@ static void perf_iommu_disable_event(struct perf_event > *event) > > static void perf_iommu_start(struct perf_event *event, int flags) > { > + u64 val; > struct hw_perf_event *hwc = &event->hw; > > if (WARN_ON_ONCE(!(hwc->state & PERF_HES_STOPPED))) > @@ -292,15 +293,16 @@ static void perf_iommu_start(struct perf_event *event, > int flags) > WARN_ON_ONCE(!(hwc->state & PERF_HES_UPTODATE)); > hwc->state = 0; > > - if (flags & PERF_EF_RELOAD) { > - u64 prev_raw_count = local64_read(&hwc->prev_count); > - amd_iommu_pc_set_reg(0, _GET_BANK(event), _GET_CNTR(event), > - IOMMU_PC_COUNTER_REG, &prev_raw_count); > - } > + if (!(flags & PERF_EF_RELOAD)) > + return; > + > + val = local64_read(&hwc->prev_count) & GENMASK_ULL(48, 0); > + if (amd_iommu_pc_set_reg(0, _GET_BANK(event), _GET_CNTR(event), > + IOMMU_PC_COUNTER_REG, &val)) > + return;
Under what conditions could this fail? ::start() is not an interface that expects failure, if we get this far, things should really just work.
