Re: [PATCH v1 5/5] xen/PMU: Cache MSR accesses during interrupthandling

From: Konrad Rzeszutek Wilk
Date: Mon Sep 23 2013 - 09:29:20 EST

On Tue, Sep 10, 2013 at 11:31:50AM -0400, Boris Ostrovsky wrote:
> 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.

Looks OK.
>
> 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
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/