Re: [PATCH v3 15/16] KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c / pmu.c

Marc Zyngier
2021-10-11T09:45:06Z

On Wed, 22 Sep 2021 01:05:32 +0100,
Sean Christopherson <seanjc@google.com> wrote:
>
> Call KVM's (un)register perf callbacks helpers directly from arm.c, and
> move the PMU bits into pmu.c and rename the related helper accordingly.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/arm64/include/asm/kvm_host.h | 3 ---
> arch/arm64/kvm/Makefile | 2 +-
> arch/arm64/kvm/arm.c | 6 ++++--
> arch/arm64/kvm/perf.c | 27 ---------------------------
> arch/arm64/kvm/pmu.c | 8 ++++++++
> include/kvm/arm_pmu.h | 1 +
> 6 files changed, 14 insertions(+), 33 deletions(-)
> delete mode 100644 arch/arm64/kvm/perf.c
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 828b6eaa2c56..f141ac65f4f1 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -670,9 +670,6 @@ unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len);
> int kvm_handle_mmio_return(struct kvm_vcpu *vcpu);
> int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa);
>
> -void kvm_perf_init(void);
> -void kvm_perf_teardown(void);
> -
> #ifdef CONFIG_GUEST_PERF_EVENTS
> static inline bool kvm_arch_pmi_in_guest(struct kvm_vcpu *vcpu)
> {
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 989bb5dad2c8..0bcc378b7961 100644
> --- a/arch/arm64/kvm/Makefile
> +++ b/arch/arm64/kvm/Makefile
> @@ -12,7 +12,7 @@ obj-$(CONFIG_KVM) += hyp/
>
> kvm-y := $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o \
> $(KVM)/vfio.o $(KVM)/irqchip.o $(KVM)/binary_stats.o \
> - arm.o mmu.o mmio.o psci.o perf.o hypercalls.o pvtime.o \
> + arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
> inject_fault.o va_layout.o handle_exit.o \
> guest.o debug.o reset.o sys_regs.o \
> vgic-sys-reg-v3.o fpsimd.o pmu.o \
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 2b542fdc237e..48f89d80f464 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1744,7 +1744,9 @@ static int init_subsystems(void)
> if (err)
> goto out;
>
> - kvm_perf_init();
> + kvm_pmu_init();
> + kvm_register_perf_callbacks(NULL);
> +
> kvm_sys_reg_table_init();
>
> out:
> @@ -2160,7 +2162,7 @@ int kvm_arch_init(void *opaque)
> /* NOP: Compiling as a module not supported */
> void kvm_arch_exit(void)
> {
> - kvm_perf_teardown();
> + kvm_unregister_perf_callbacks();
> }
>
> static int __init early_kvm_mode_cfg(char *arg)
> diff --git a/arch/arm64/kvm/perf.c b/arch/arm64/kvm/perf.c
> deleted file mode 100644
> index 0b902e0d5b5d..000000000000
> --- a/arch/arm64/kvm/perf.c
> +++ /dev/null
> @@ -1,27 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0-only
> -/*
> - * Based on the x86 implementation.
> - *
> - * Copyright (C) 2012 ARM Ltd.
> - * Author: Marc Zyngier <marc.zyngier@arm.com>
> - */
> -
> -#include <linux/perf_event.h>
> -#include <linux/kvm_host.h>
> -
> -#include <asm/kvm_emulate.h>
> -
> -DEFINE_STATIC_KEY_FALSE(kvm_arm_pmu_available);
> -
> -void kvm_perf_init(void)
> -{
> - if (kvm_pmu_probe_pmuver() != 0xf && !is_protected_kvm_enabled())
> - static_branch_enable(&kvm_arm_pmu_available);
> -
> - kvm_register_perf_callbacks(NULL);
> -}
> -
> -void kvm_perf_teardown(void)
> -{
> - kvm_unregister_perf_callbacks();
> -}
> diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
> index 03a6c1f4a09a..d98b57a17043 100644
> --- a/arch/arm64/kvm/pmu.c
> +++ b/arch/arm64/kvm/pmu.c
> @@ -7,6 +7,14 @@
> #include <linux/perf_event.h>
> #include <asm/kvm_hyp.h>
>
> +DEFINE_STATIC_KEY_FALSE(kvm_arm_pmu_available);
> +
> +void kvm_pmu_init(void)
> +{
> + if (kvm_pmu_probe_pmuver() != 0xf && !is_protected_kvm_enabled())
> + static_branch_enable(&kvm_arm_pmu_available);
> +}
> +
> /*
> * Given the perf event attributes and system type, determine
> * if we are going to need to switch counters at guest entry/exit.
> diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
> index 864b9997efb2..42270676498d 100644
> --- a/include/kvm/arm_pmu.h
> +++ b/include/kvm/arm_pmu.h
> @@ -14,6 +14,7 @@
> #define ARMV8_PMU_MAX_COUNTER_PAIRS ((ARMV8_PMU_MAX_COUNTERS + 1) >> 1)
>
> DECLARE_STATIC_KEY_FALSE(kvm_arm_pmu_available);
> +void kvm_pmu_init(void);
>
> static __always_inline bool kvm_arm_support_pmu_v3(void)
> {

Note that this patch is now conflicting with e840f42a4992 ("KVM:
arm64: Fix PMU probe ordering"), which was merged in -rc4. Moving the
static key definition to arch/arm64/kvm/pmu-emul.c and getting rid of
kvm_pmu_init() altogether should be enough to resolve it.

With that,

Reviewed-by: Marc Zyngier <maz@kernel.org>

M.

--
Without deviation from the norm, progress is not possible.