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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 autolearn=unavailable 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 B3650C41517 for ; Sun, 4 Aug 2019 09:54:16 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 3D1A8206C1 for ; Sun, 4 Aug 2019 09:54:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D1A8206C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 74F644A525; Sun, 4 Aug 2019 05:54:15 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VevrofOAIW5Q; Sun, 4 Aug 2019 05:54:14 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 45C774A54D; Sun, 4 Aug 2019 05:54:14 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id A100F4A563 for ; Sun, 4 Aug 2019 05:54:12 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id IH1wRrSBlzt9 for ; Sun, 4 Aug 2019 05:54:11 -0400 (EDT) Received: from inca-roads.misterjones.org (inca-roads.misterjones.org [213.251.177.50]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 19C0A4A525 for ; Sun, 4 Aug 2019 05:54:11 -0400 (EDT) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why) by cheepnis.misterjones.org with esmtpsa (TLSv1.2:AES256-GCM-SHA384:256) (Exim 4.80) (envelope-from ) id 1huDDA-0003Vy-Mt; Sun, 04 Aug 2019 11:53:59 +0200 Date: Sun, 4 Aug 2019 10:53:53 +0100 From: Marc Zyngier To: Steven Price Subject: Re: [PATCH 9/9] arm64: Retrieve stolen time as paravirtualized guest Message-ID: <20190804105353.5e9824dc@why> In-Reply-To: <20190802145017.42543-10-steven.price@arm.com> References: <20190802145017.42543-1-steven.price@arm.com> <20190802145017.42543-10-steven.price@arm.com> Organization: Approximate X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: steven.price@arm.com, catalin.marinas@arm.com, pbonzini@redhat.com, rkrcmar@redhat.com, linux@armlinux.org.uk, will@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false Cc: kvm@vger.kernel.org, Catalin Marinas , linux-doc@vger.kernel.org, Russell King , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Fri, 2 Aug 2019 15:50:17 +0100 Steven Price wrote: > Enable paravirtualization features when running under a hypervisor > supporting the PV_TIME_ST hypercall. > > For each (v)CPU, we ask the hypervisor for the location of a shared > page which the hypervisor will use to report stolen time to us. We set > pv_time_ops to the stolen time function which simply reads the stolen > value from the shared page for a VCPU. We guarantee single-copy > atomicity using READ_ONCE which means we can also read the stolen > time for another VCPU than the currently running one while it is > potentially being updated by the hypervisor. > > Signed-off-by: Steven Price > --- > arch/arm64/kernel/Makefile | 1 + > arch/arm64/kernel/kvm.c | 155 +++++++++++++++++++++++++++++++++++++ nit: Why not using paravirt.c, which clearly states what it does? The alternative would be to name it kvm-pv.c. > include/linux/cpuhotplug.h | 1 + > 3 files changed, 157 insertions(+) > create mode 100644 arch/arm64/kernel/kvm.c > > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile > index 478491f07b4f..eb36edf9b930 100644 > --- a/arch/arm64/kernel/Makefile > +++ b/arch/arm64/kernel/Makefile > @@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o > obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o > obj-$(CONFIG_ARM64_SSBD) += ssbd.o > obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o > +obj-$(CONFIG_PARAVIRT) += kvm.o > > obj-y += vdso/ probes/ > obj-$(CONFIG_COMPAT_VDSO) += vdso32/ > diff --git a/arch/arm64/kernel/kvm.c b/arch/arm64/kernel/kvm.c > new file mode 100644 > index 000000000000..245398c79dae > --- /dev/null > +++ b/arch/arm64/kernel/kvm.c > @@ -0,0 +1,155 @@ > +// SPDX-License-Identifier: GPL-2.0 > +// Copyright (C) 2019 Arm Ltd. > + > +#define pr_fmt(fmt) "kvmarm-pv: " fmt > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#include > +#include > +#include > + > +struct kvmarm_stolen_time_region { > + struct pvclock_vcpu_stolen_time_info *kaddr; > +}; > + > +static DEFINE_PER_CPU(struct kvmarm_stolen_time_region, stolen_time_region); > + > +static bool steal_acc = true; > +static int __init parse_no_stealacc(char *arg) > +{ > + steal_acc = false; > + return 0; > +} > +early_param("no-steal-acc", parse_no_stealacc); > + > +/* return stolen time in ns by asking the hypervisor */ > +static u64 kvm_steal_clock(int cpu) > +{ > + struct kvmarm_stolen_time_region *reg; > + > + reg = per_cpu_ptr(&stolen_time_region, cpu); > + if (!reg->kaddr) { > + pr_warn_once("stolen time enabled but not configured for cpu %d\n", > + cpu); > + return 0; > + } > + > + return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time)); > +} > + > +static int disable_stolen_time_current_cpu(void) > +{ > + struct kvmarm_stolen_time_region *reg; > + > + reg = this_cpu_ptr(&stolen_time_region); > + if (!reg->kaddr) > + return 0; > + > + memunmap(reg->kaddr); > + memset(reg, 0, sizeof(*reg)); > + > + return 0; > +} > + > +static int stolen_time_dying_cpu(unsigned int cpu) > +{ > + return disable_stolen_time_current_cpu(); > +} > + > +static int init_stolen_time_cpu(unsigned int cpu) > +{ > + struct kvmarm_stolen_time_region *reg; > + struct arm_smccc_res res; > + > + reg = this_cpu_ptr(&stolen_time_region); > + > + if (reg->kaddr) > + return 0; Can this actually happen? It'd take two CPU_UP calls from the HP notifiers to get in that situation... > + > + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res); > + > + if ((long)res.a0 < 0) > + return -EINVAL; > + > + reg->kaddr = memremap(res.a0, > + sizeof(struct pvclock_vcpu_stolen_time_info), > + MEMREMAP_WB); > + > + if (reg->kaddr == NULL) { > + pr_warn("Failed to map stolen time data structure\n"); > + return -EINVAL; -ENOMEM is the expected return code. > + } > + > + if (le32_to_cpu(reg->kaddr->revision) != 0 || > + le32_to_cpu(reg->kaddr->attributes) != 0) { > + pr_warn("Unexpected revision or attributes in stolen time data\n"); > + return -ENXIO; > + } > + > + return 0; > +} > + > +static int kvm_arm_init_stolen_time(void) > +{ > + int ret; > + > + ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING, > + "hypervisor/kvmarm/pv:starting", > + init_stolen_time_cpu, stolen_time_dying_cpu); > + if (ret < 0) > + return ret; > + return 0; > +} > + > +static bool has_kvm_steal_clock(void) > +{ > + struct arm_smccc_res res; > + > + /* To detect the presence of PV time support we require SMCCC 1.1+ */ > + if (psci_ops.smccc_version < SMCCC_VERSION_1_1) > + return false; > + > + arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, > + ARM_SMCCC_HV_PV_FEATURES, &res); > + > + if (res.a0 != SMCCC_RET_SUCCESS) > + return false; > + > + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_FEATURES, > + ARM_SMCCC_HV_PV_TIME_ST, &res); > + > + if (res.a0 != SMCCC_RET_SUCCESS) > + return false; > + > + return true; > +} > + > +static int __init kvm_guest_init(void) > +{ > + int ret = 0; > + > + if (!has_kvm_steal_clock()) > + return 0; > + > + ret = kvm_arm_init_stolen_time(); > + if (ret) > + return ret; > + > + pv_ops.time.steal_clock = kvm_steal_clock; > + > + static_key_slow_inc(¶virt_steal_enabled); > + if (steal_acc) > + static_key_slow_inc(¶virt_steal_rq_enabled); > + > + pr_info("using stolen time PV\n"); > + > + return 0; > +} > +early_initcall(kvm_guest_init); Is there any reason why we wouldn't directly call into this rather than using an initcall? > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h > index 068793a619ca..89d75edb5750 100644 > --- a/include/linux/cpuhotplug.h > +++ b/include/linux/cpuhotplug.h > @@ -136,6 +136,7 @@ enum cpuhp_state { > /* Must be the last timer callback */ > CPUHP_AP_DUMMY_TIMER_STARTING, > CPUHP_AP_ARM_XEN_STARTING, > + CPUHP_AP_ARM_KVMPV_STARTING, > CPUHP_AP_ARM_CORESIGHT_STARTING, > CPUHP_AP_ARM64_ISNDEP_STARTING, > CPUHP_AP_SMPCFD_DYING, Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm