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Thu, 08 Jul 2021 21:37:38 -0700 (PDT) From: Sergey Senozhatsky To: Marc Zyngier , Will Deacon Cc: Suleiman Souhlal , Joel Fernandes , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Sergey Senozhatsky Subject: [PATCHv2 2/4] arm64: add guest pvstate support Date: Fri, 9 Jul 2021 13:37:11 +0900 Message-Id: <20210709043713.887098-3-senozhatsky@chromium.org> X-Mailer: git-send-email 2.32.0.93.g670b81a890-goog In-Reply-To: <20210709043713.887098-1-senozhatsky@chromium.org> References: <20210709043713.887098-1-senozhatsky@chromium.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210708_213739_466990_4AEB4F99 X-CRM114-Status: GOOD ( 17.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org PV-vcpu-state is a per-CPU struct, which, for the time being, holds boolean `preempted' vCPU state. During the startup, given that host supports PV-state, each guest vCPU sends a pointer to its per-CPU variable to the host as a payload with the SMCCC HV call, so that host can update vCPU state when it puts or loads vCPU. This has impact on the guest's scheduler: [..] wake_up_process() try_to_wake_up() select_task_rq_fair() available_idle_cpu() vcpu_is_preempted() Some sched benchmarks data is available on the github page [0]. [0] https://github.com/sergey-senozhatsky/arm64-vcpu_is_preempted Signed-off-by: Sergey Senozhatsky --- arch/arm64/include/asm/paravirt.h | 19 +++++++ arch/arm64/kernel/paravirt.c | 94 +++++++++++++++++++++++++++++++ arch/arm64/kernel/smp.c | 4 ++ 3 files changed, 117 insertions(+) diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h index 9aa193e0e8f2..a3f7665dff38 100644 --- a/arch/arm64/include/asm/paravirt.h +++ b/arch/arm64/include/asm/paravirt.h @@ -2,6 +2,11 @@ #ifndef _ASM_ARM64_PARAVIRT_H #define _ASM_ARM64_PARAVIRT_H +struct vcpu_state { + bool preempted; + u8 reserved[63]; +}; + #ifdef CONFIG_PARAVIRT #include @@ -20,8 +25,22 @@ static inline u64 paravirt_steal_clock(int cpu) int __init pv_time_init(void); +bool dummy_vcpu_is_preempted(unsigned int cpu); + +extern struct static_key pv_vcpu_is_preempted_enabled; +DECLARE_STATIC_CALL(pv_vcpu_is_preempted, dummy_vcpu_is_preempted); + +static inline bool paravirt_vcpu_is_preempted(unsigned int cpu) +{ + return static_call(pv_vcpu_is_preempted)(cpu); +} + +int __init pv_vcpu_state_init(void); + #else +#define pv_vcpu_state_init() do {} while (0) + #define pv_time_init() do {} while (0) #endif // CONFIG_PARAVIRT diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c index 75fed4460407..d8fc46795d94 100644 --- a/arch/arm64/kernel/paravirt.c +++ b/arch/arm64/kernel/paravirt.c @@ -40,6 +40,11 @@ struct pv_time_stolen_time_region { static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region); +static DEFINE_PER_CPU(struct vcpu_state, vcpus_states); +struct static_key pv_vcpu_is_preempted_enabled; + +DEFINE_STATIC_CALL(pv_vcpu_is_preempted, dummy_vcpu_is_preempted); + static bool steal_acc = true; static int __init parse_no_stealacc(char *arg) { @@ -165,3 +170,92 @@ int __init pv_time_init(void) return 0; } + +bool dummy_vcpu_is_preempted(unsigned int cpu) +{ + return false; +} + +static bool __vcpu_is_preempted(unsigned int cpu) +{ + struct vcpu_state *st; + + st = &per_cpu(vcpus_states, cpu); + return READ_ONCE(st->preempted); +} + +static bool has_pv_vcpu_state(void) +{ + struct arm_smccc_res res; + + /* To detect the presence of PV time support we require SMCCC 1.1+ */ + if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE) + return false; + + arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, + ARM_SMCCC_HV_PV_VCPU_STATE_FEATURES, + &res); + + if (res.a0 != SMCCC_RET_SUCCESS) + return false; + return true; +} + +static int __pv_vcpu_state_hook(unsigned int cpu, int event) +{ + struct arm_smccc_res res; + struct vcpu_state *st; + + st = &per_cpu(vcpus_states, cpu); + arm_smccc_1_1_invoke(event, virt_to_phys(st), &res); + if (res.a0 != SMCCC_RET_SUCCESS) + return -EINVAL; + return 0; +} + +static int vcpu_state_init(unsigned int cpu) +{ + int ret = __pv_vcpu_state_hook(cpu, ARM_SMCCC_HV_PV_VCPU_STATE_INIT); + + if (ret) + pr_warn("Unable to ARM_SMCCC_HV_PV_STATE_INIT\n"); + return ret; +} + +static int vcpu_state_release(unsigned int cpu) +{ + int ret = __pv_vcpu_state_hook(cpu, ARM_SMCCC_HV_PV_VCPU_STATE_RELEASE); + + if (ret) + pr_warn("Unable to ARM_SMCCC_HV_PV_STATE_RELEASE\n"); + return ret; +} + +static int pv_vcpu_state_register_hooks(void) +{ + int ret; + + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, + "hypervisor/arm/pvstate:starting", + vcpu_state_init, + vcpu_state_release); + if (ret < 0) + pr_warn("Failed to register CPU hooks\n"); + return 0; +} + +int __init pv_vcpu_state_init(void) +{ + int ret; + + if (!has_pv_vcpu_state()) + return 0; + + ret = pv_vcpu_state_register_hooks(); + if (ret) + return ret; + + static_call_update(pv_vcpu_is_preempted, __vcpu_is_preempted); + static_key_slow_inc(&pv_vcpu_is_preempted_enabled); + return 0; +} diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 6f6ff072acbd..20d42e0f2a99 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -50,6 +50,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -756,6 +757,9 @@ void __init smp_prepare_cpus(unsigned int max_cpus) numa_store_cpu_info(this_cpu); numa_add_cpu(this_cpu); + /* Init paravirt CPU state */ + pv_vcpu_state_init(); + /* * If UP is mandated by "nosmp" (which implies "maxcpus=0"), don't set * secondary CPUs present.