On 11/20/2018 02:15 PM, Andrew Murray wrote:
Add support for the :G and :H attributes in perf by handling the
exclude_host/exclude_guest event attributes.
We notify KVM of counters that we wish to be enabled or disabled on
guest entry/exit and thus defer from starting or stopping :G events
as per the events exclude_host attribute.
When using VHE, EL2 is unused by the guest - therefore we can filter
out these events with the PMU as per the 'exclude_host' attribute.
With both VHE and non-VHE we switch the counters between host/guest
at EL2. With non-VHE when using 'exclude_host' we filter out EL2.
These changes eliminate counters counting host events on the
boundaries of guest entry/exit when using :G. However when using :H
unless exclude_hv is set on non-VHE then there is a small blackout
window at the guest entry/exit where host events are not captured.
Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx>
---
arch/arm64/kernel/perf_event.c | 41 +++++++++++++++++++++++++++++++++++------
1 file changed, 35 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index de564ae..412bd80 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -26,6 +26,7 @@
#include <linux/acpi.h>
#include <linux/clocksource.h>
+#include <linux/kvm_host.h>
#include <linux/of.h>
#include <linux/perf/arm_pmu.h>
#include <linux/platform_device.h>
@@ -647,11 +648,23 @@ static inline int armv8pmu_enable_counter(int idx)
static inline void armv8pmu_enable_event_counter(struct perf_event *event)
{
+ struct perf_event_attr *attr = &event->attr;
int idx = event->hw.idx;
+ u32 counter_bits = BIT(ARMV8_IDX_TO_COUNTER(idx));
- armv8pmu_enable_counter(idx);
if (armv8pmu_event_is_chained(event))
- armv8pmu_enable_counter(idx - 1);
+ counter_bits |= BIT(ARMV8_IDX_TO_COUNTER(idx - 1));
minor nit: If you rearrange the code below a bit
+
+ if (attr->exclude_host)
+ kvm_set_clr_guest_pmu_events(0, counter_bits);
+ if (attr->exclude_guest)
+ kvm_set_clr_host_pmu_events(0, counter_bits);
+
+ if (!attr->exclude_host) {
+ armv8pmu_enable_counter(idx);
+ if (armv8pmu_event_is_chained(event))
+ armv8pmu_enable_counter(idx - 1);
we could have :
if (attr->exclude_guest)
kvm_set_clr_host_pmu_events(0, counter_bits);
if (attr->exclude_host) {
kvm_set_clr_guest_pmu_events(0, counter_bits);
return;
}
armv8pmu_enable_counter(idx);
if (armv8pmu_event_is_chained(event))
armv8pmu_enable_counter(idx - 1);
Similarly for disable_event_counter.
+ }
}
static inline int armv8pmu_disable_counter(int idx)
@@ -664,11 +677,23 @@ static inline int armv8pmu_disable_counter(int idx)
static inline void armv8pmu_disable_event_counter(struct perf_event *event)
{
struct hw_perf_event *hwc = &event->hw;
+ struct perf_event_attr *attr = &event->attr;
int idx = hwc->idx;
+ u32 counter_bits = BIT(ARMV8_IDX_TO_COUNTER(idx));
if (armv8pmu_event_is_chained(event))
- armv8pmu_disable_counter(idx - 1);
- armv8pmu_disable_counter(idx);
+ counter_bits |= BIT(ARMV8_IDX_TO_COUNTER(idx - 1));
+
+ if (attr->exclude_host)
+ kvm_set_clr_guest_pmu_events(counter_bits, 0);
+ if (attr->exclude_guest)
+ kvm_set_clr_host_pmu_events(counter_bits, 0);
+
+ if (!attr->exclude_host) {
+ if (armv8pmu_event_is_chained(event))
+ armv8pmu_disable_counter(idx - 1);
+ armv8pmu_disable_counter(idx);
+ }
}
static inline int armv8pmu_enable_intens(int idx)
@@ -945,12 +970,12 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
* with other architectures (x86 and Power).
*/
if (is_kernel_in_hyp_mode()) {
- if (!attr->exclude_kernel)
+ if (!attr->exclude_kernel && !attr->exclude_host)
config_base |= ARMV8_PMU_INCLUDE_EL2;
Shouldn't we handle "exclude_kernel" for a "Guest" event ?
i.e, what if we have exclude_kernel + exclude_host set ? Doesn't
the "exclude_kernel" apply to the event filtering after we enter
guest and thus, we need to set the EXCLUDE_EL1 ?
Also I am wondering what is the situation with Nested virtualisation
coming in. i.e, if the host hyp wanted to profile the guest hyp, should
we set EL2 events ? I understand this is something which should be
solved with the nested virt changes. But it would be good to see
if we could filter "exclude_host" and "exclude_guest" at the hypervisor
level (i.e, in software, without PMU filtering) to allow the normal
controls to make use of the hardware filtering ?
} else {
if (attr->exclude_kernel)
config_base |= ARMV8_PMU_EXCLUDE_EL1;
- if (!attr->exclude_hv)
+ if (!attr->exclude_hv && !attr->exclude_host)
config_base |= ARMV8_PMU_INCLUDE_EL2;
}
if (attr->exclude_user)
@@ -976,6 +1001,10 @@ static void armv8pmu_reset(void *info)
armv8pmu_disable_intens(idx);
}
+ /* Clear the counters we flip at guest entry/exit */
+ kvm_set_clr_host_pmu_events(U32_MAX, 0);
+ kvm_set_clr_guest_pmu_events(U32_MAX, 0);
+
/*
* Initialize & Reset PMNC. Request overflow interrupt for
* 64 bit cycle counter but cheat in armv8pmu_write_counter().
Suzuki
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