On Sun, Sep 9, 2012 at 5:18 PM, Christoffer Dall
<c.dall@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> 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?
>
oh, never mind about this, I didn't get that this is in fact call from
an ISR and thus we must be in the process that still holds that file
descriptor. sorry about the noise.
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
