[PATCH v8 7/9] perf/amd/iommu: Check return value when set and get counter value

Suravee Suthikulpanit
2017-01-16T07:25:01Z

From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

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 <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
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;

perf_iommu_enable_event(event);
perf_event_update_userpage(event);
-
}

static void perf_iommu_read(struct perf_event *event)
@@ -309,8 +311,9 @@ static void perf_iommu_read(struct perf_event *event)
s64 delta;
struct hw_perf_event *hwc = &event->hw;

- amd_iommu_pc_get_reg(0, _GET_BANK(event), _GET_CNTR(event),
- IOMMU_PC_COUNTER_REG, &count);
+ if (amd_iommu_pc_get_reg(0, _GET_BANK(event), _GET_CNTR(event),
+ IOMMU_PC_COUNTER_REG, &count))
+ return;

/* IOMMU pc counter register is only 48 bits */
count &= GENMASK_ULL(48, 0);
--
1.8.3.1