[PATCH v1 5/5] xen/PMU: Cache MSR accesses during interrupt handling

From: Boris Ostrovsky
Date: Tue Sep 10 2013 - 11:30:24 EST


Avoid trapping to hypervisor on each MSR access during interrupt handling.
Instead, use cached MSR values provided in shared xenpmu_data by Xen. When
handling is completed, flush the registers to hypervisor who will load them
into HW.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
arch/x86/xen/pmu.c | 15 ++++++++++++++-
include/xen/interface/xenpmu.h | 1 +
2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c
index d8b059b..bdd7c4a 100644
--- a/arch/x86/xen/pmu.c
+++ b/arch/x86/xen/pmu.c
@@ -345,14 +345,27 @@ static void xen_convert_regs(struct cpu_user_regs *xen_regs,

irqreturn_t xen_pmu_irq_handler(int irq, void *dev_id)
{
- int ret = IRQ_NONE;
+ int err, ret = IRQ_NONE;
struct pt_regs regs;
struct xenpmu_data *xenpmu_data = per_cpu(xenpmu_shared,
smp_processor_id());

+ /*
+ * While handling the interrupt MSR accesses will be cached
+ * in PMU context
+ */
+ xenpmu_data->pmu_flags |= PMU_CACHED;
xen_convert_regs(&xenpmu_data->regs, &regs);
if (x86_pmu.handle_irq(&regs))
ret = IRQ_HANDLED;
+ xenpmu_data->pmu_flags &= ~PMU_CACHED;
+
+ /* Write out cached context to HW */
+ err = HYPERVISOR_xenpmu_op(XENPMU_flush, NULL);
+ if (err) {
+ WARN(1, "%s failed hypercall, err: %d\n", __func__, err);
+ return IRQ_NONE;
+ }

return ret;
}
diff --git a/include/xen/interface/xenpmu.h b/include/xen/interface/xenpmu.h
index 16fe1ab..ec0e802 100644
--- a/include/xen/interface/xenpmu.h
+++ b/include/xen/interface/xenpmu.h
@@ -16,6 +16,7 @@
#define XENPMU_init 4
#define XENPMU_finish 5
#define XENPMU_lvtpc_set 6
+#define XENPMU_flush 7 /* Write cached MSR values to HW */

/* Parameter structure for HYPERVISOR_xenpmu_op call */
struct xenpmu_params {
--
1.8.1.4

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