From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2508FC07E99 for ; Fri, 9 Jul 2021 07:39:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB4F061370 for ; Fri, 9 Jul 2021 07:39:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231265AbhGIHmO (ORCPT ); Fri, 9 Jul 2021 03:42:14 -0400 Received: from wforward3-smtp.messagingengine.com ([64.147.123.22]:34431 "EHLO wforward3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230505AbhGIHmN (ORCPT ); Fri, 9 Jul 2021 03:42:13 -0400 Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailforward.west.internal (Postfix) with ESMTP id D094C1AC0BB7; Fri, 9 Jul 2021 03:39:28 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute1.internal (MEProxy); Fri, 09 Jul 2021 03:39:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm3; bh=MmHFnw D/vmxcyGTiVsUB3xcr0vIvVuonBri13Nc/hoQ=; b=dm42RkXa9CJmEzzkU8nqBu tNmNCcqCxT7yDVOKm0rew1blS/qzmArSFBYihxyR8jY6xHecfphzeTr1BWoUvP27 vvdpcxWgnzvfdq6C6n7rlCEIZ045x5Ia/p8dijh9lwLdQuAB+E0NUKjgqMPB56nf jUN3izzXUx0iQkW7g4akBMBaMXSHmm4rbTaJ8mYkg2kP0sB4jcYMDM35gEJjwMql 4Gv5QcBCEMa8PoSPH7vo1tciAaAkcMO1chF2J2dfJCl29FnWlVVoLNVQiyBCa7xC Sse7KZbVp1CdUxbAM1DpyzxGb6fFswBwFlujO1LXbQsrMiglpBB95YT9sjMl14rA == X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvtddrtdehgdelgecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpefvufgjfhfhfffkgggtsehttdertddttddtnecuhfhrohhmpeffrghvihguucfg ughmohhnughsohhnuceoughmvgesughmvgdrohhrgheqnecuggftrfgrthhtvghrnheptd dtgedttefhfeeugefffffffedvueekgfduhfevueehvdekveeitdelledvteetnecuffho mhgrihhnpehgihhthhhusgdrtghomhenucevlhhushhtvghrufhiiigvpedtnecurfgrrh grmhepmhgrihhlfhhrohhmpegumhgvsegumhgvrdhorhhg X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Fri, 9 Jul 2021 03:39:26 -0400 (EDT) Received: from localhost (disaster-area.hh.sledj.net [local]) by disaster-area.hh.sledj.net (OpenSMTPD) with ESMTPA id 58528b94; Fri, 9 Jul 2021 07:39:25 +0000 (UTC) To: Sergey Senozhatsky , 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: Re: [PATCHv2 2/4] arm64: add guest pvstate support In-Reply-To: <20210709043713.887098-3-senozhatsky@chromium.org> References: <20210709043713.887098-1-senozhatsky@chromium.org> <20210709043713.887098-3-senozhatsky@chromium.org> X-HGTTG: heart-of-gold From: David Edmondson Date: Fri, 09 Jul 2021 08:39:25 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday, 2021-07-09 at 13:37:11 +09, Sergey Senozhatsky wrote: > 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+ */ "PV VCPU state support" rather than "PV time support". > + 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"); Include that it's PV VCPU state hooks? > + 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. > -- > 2.32.0.93.g670b81a890-goog dme. -- If I could buy my reasoning, I'd pay to lose.