On Thu, Sep 6, 2012 at 1:16 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> In order to be able to correctly profile what is happening on the
> host, we need to be able to identify when we're running on the guest,
> and log these events differently.
>
> Perf offers a simple way to register callbacks into KVM. Mimic what
> x86 does and enjoy being able to profile your KVM host.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_host.h | 3 ++
> arch/arm/kvm/Makefile | 2 +-
> arch/arm/kvm/arm.c | 5 ++-
> arch/arm/kvm/perf.c | 70 +++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 78 insertions(+), 2 deletions(-)
> create mode 100644 arch/arm/kvm/perf.c
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 4302007..32299c1 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -207,4 +207,7 @@ static inline int kvm_test_age_hva(struct kvm *kvm, unsigned long hva)
> struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
> struct kvm_vcpu __percpu **kvm_get_running_vcpus(void);
>
> +int kvm_perf_init(void);
> +int kvm_perf_teardown(void);
> +
> #endif /* __ARM_KVM_HOST_H__ */
> diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
> index 4f27970..73c268a 100644
> --- a/arch/arm/kvm/Makefile
> +++ b/arch/arm/kvm/Makefile
> @@ -18,7 +18,7 @@ obj-$(CONFIG_KVM_ARM_HOST) += init.o interrupts.o exports.o
>
> kvm-arm-y += $(addprefix ../../../virt/kvm/, kvm_main.o coalesced_mmio.o)
>
> -kvm-arm-y += arm.o guest.o mmu.o emulate.o reset.o coproc.o
> +kvm-arm-y += arm.o guest.o mmu.o emulate.o reset.o coproc.o perf.o
>
> obj-$(CONFIG_KVM) += kvm-arm.o
> obj-$(CONFIG_KVM_ARM_VGIC) += vgic.o
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 8d8bf72..743bdc8 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -995,7 +995,9 @@ static int init_hyp_mode(void)
> err = kvm_timer_hyp_init();
> if (err)
> goto out_free_mappings;
> -
> +
> + kvm_perf_init();
> +
> return 0;
> out_free_vfp:
> free_percpu(kvm_host_vfp_state);
> @@ -1090,6 +1092,7 @@ void kvm_arch_exit(void)
> free_page(per_cpu(kvm_arm_hyp_stack_page, cpu));
> per_cpu(kvm_arm_hyp_stack_page, cpu) = 0;
> }
> + kvm_perf_teardown();
> }
>
> static int arm_init(void)
> diff --git a/arch/arm/kvm/perf.c b/arch/arm/kvm/perf.c
seems a bit overkill with a separate file, I would prefer if this was
just in arm.c
> new file mode 100644
> index 0000000..e7c42fd
> --- /dev/null
> +++ b/arch/arm/kvm/perf.c
> @@ -0,0 +1,70 @@
> +/*
> + * Based on the x86 implementation.
> + *
> + * Copyright (C) 2012 ARM Ltd.
> + * Author: Marc Zyngier <marc.zyngier@xxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> + */
> +
> +#include <linux/perf_event.h>
> +
> +#include <asm/ptrace.h>
> +#include <asm/kvm_host.h>
> +#include <asm/kvm_emulate.h>
> +
> +static int kvm_is_in_guest(void)
> +{
> + return kvm_arm_get_running_vcpu() != NULL;
> +}
> +
> +static int kvm_is_user_mode(void)
> +{
> + struct kvm_vcpu *vcpu;
> +
> + vcpu = kvm_arm_get_running_vcpu();
> +
> + if (vcpu)
> + return (*vcpu_cpsr(vcpu) & MODE_MASK) == USR_MODE;
isn't this completely racy if the vcpu is freed from under your?
> +
> + return 0;
> +}
> +
> +static unsigned long kvm_get_guest_ip(void)
> +{
> + struct kvm_vcpu *vcpu;
> +
> + vcpu = kvm_arm_get_running_vcpu();
> +
> + if (vcpu)
> + return *vcpu_pc(vcpu);
ditto?
> +
> + return 0;
> +}
> +
> +static struct perf_guest_info_callbacks kvm_guest_cbs = {
> + .is_in_guest = kvm_is_in_guest,
> + .is_user_mode = kvm_is_user_mode,
> + .get_guest_ip = kvm_get_guest_ip,
> +};
> +
> +int kvm_perf_init(void)
> +{
> + return perf_register_guest_info_callbacks(&kvm_guest_cbs);
> +}
> +
> +int kvm_perf_teardown(void)
> +{
> + return perf_unregister_guest_info_callbacks(&kvm_guest_cbs);
> +}
> --
> 1.7.12
>
>
>
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