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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 59F2BC33CA2 for ; Fri, 10 Jan 2020 10:54:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2BDE420848 for ; Fri, 10 Jan 2020 10:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727784AbgAJKyj (ORCPT ); Fri, 10 Jan 2020 05:54:39 -0500 Received: from foss.arm.com ([217.140.110.172]:42300 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727365AbgAJKyj (ORCPT ); Fri, 10 Jan 2020 05:54:39 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2A0C2328; Fri, 10 Jan 2020 02:54:38 -0800 (PST) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9E5433F703; Fri, 10 Jan 2020 02:54:37 -0800 (PST) Date: Fri, 10 Jan 2020 10:54:36 +0000 From: Andrew Murray To: Marc Zyngier Cc: Catalin Marinas , Mark Rutland , will@kernel.org, Sudeep Holla , kvm@vger.kernel.org, kvmarm , linux-arm-kernel , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 09/18] arm64: KVM: enable conditional save/restore full SPE profiling buffer controls Message-ID: <20200110105435.GC42593@e119886-lin.cambridge.arm.com> References: <20191220143025.33853-1-andrew.murray@arm.com> <20191220143025.33853-10-andrew.murray@arm.com> <20191221141325.5a177343@why> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191221141325.5a177343@why> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 21, 2019 at 02:13:25PM +0000, Marc Zyngier wrote: > On Fri, 20 Dec 2019 14:30:16 +0000 > Andrew Murray wrote: > > [somehow managed not to do a reply all, re-sending] > > > From: Sudeep Holla > > > > Now that we can save/restore the full SPE controls, we can enable it > > if SPE is setup and ready to use in KVM. It's supported in KVM only if > > all the CPUs in the system supports SPE. > > > > However to support heterogenous systems, we need to move the check if > > host supports SPE and do a partial save/restore. > > No. Let's just not go down that path. For now, KVM on heterogeneous > systems do not get SPE. If SPE has been enabled on a guest and a CPU > comes up without SPE, this CPU should fail to boot (same as exposing a > feature to userspace). > > > > > Signed-off-by: Sudeep Holla > > Signed-off-by: Andrew Murray > > --- > > arch/arm64/kvm/hyp/debug-sr.c | 33 ++++++++++++++++----------------- > > include/kvm/arm_spe.h | 6 ++++++ > > 2 files changed, 22 insertions(+), 17 deletions(-) > > > > diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c > > index 12429b212a3a..d8d857067e6d 100644 > > --- a/arch/arm64/kvm/hyp/debug-sr.c > > +++ b/arch/arm64/kvm/hyp/debug-sr.c > > @@ -86,18 +86,13 @@ > > } > > > > static void __hyp_text > > -__debug_save_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > +__debug_save_spe_context(struct kvm_cpu_context *ctxt, bool full_ctxt) > > { > > u64 reg; > > > > /* Clear pmscr in case of early return */ > > ctxt->sys_regs[PMSCR_EL1] = 0; > > > > - /* SPE present on this CPU? */ > > - if (!cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1), > > - ID_AA64DFR0_PMSVER_SHIFT)) > > - return; > > - > > /* Yes; is it owned by higher EL? */ > > reg = read_sysreg_s(SYS_PMBIDR_EL1); > > if (reg & BIT(SYS_PMBIDR_EL1_P_SHIFT)) > > @@ -142,7 +137,7 @@ __debug_save_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > } > > > > static void __hyp_text > > -__debug_restore_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > +__debug_restore_spe_context(struct kvm_cpu_context *ctxt, bool full_ctxt) > > { > > if (!ctxt->sys_regs[PMSCR_EL1]) > > return; > > @@ -210,11 +205,14 @@ void __hyp_text __debug_restore_guest_context(struct kvm_vcpu *vcpu) > > struct kvm_guest_debug_arch *host_dbg; > > struct kvm_guest_debug_arch *guest_dbg; > > > > + host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > + guest_ctxt = &vcpu->arch.ctxt; > > + > > + __debug_restore_spe_context(guest_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > + > > if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)) > > return; > > > > - host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > - guest_ctxt = &vcpu->arch.ctxt; > > host_dbg = &vcpu->arch.host_debug_state.regs; > > guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr); > > > > @@ -232,8 +230,7 @@ void __hyp_text __debug_restore_host_context(struct kvm_vcpu *vcpu) > > host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > guest_ctxt = &vcpu->arch.ctxt; > > > > - if (!has_vhe()) > > - __debug_restore_spe_nvhe(host_ctxt, false); > > + __debug_restore_spe_context(host_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > So you now do an unconditional save/restore on the exit path for VHE as > well? Even if the host isn't using the SPE HW? That's not acceptable > as, in most cases, only the host /or/ the guest will use SPE. Here, you > put a measurable overhead on each exit. > > If the host is not using SPE, then the restore/save should happen in > vcpu_load/vcpu_put. Only if the host is using SPE should you do > something in the run loop. Of course, this only applies to VHE and > non-VHE must switch eagerly. > On VHE where SPE is used in the guest only - we save/restore in vcpu_load/put. On VHE where SPE is used in the host only - we save/restore in the run loop. On VHE where SPE is used in guest and host - we save/restore in the run loop. As the guest can't trace EL2 it doesn't matter if we restore guest SPE early in the vcpu_load/put functions. (I assume it doesn't matter that we restore an EL0/EL1 profiling buffer address at this point and enable tracing given that there is nothing to trace until entering the guest). However the reason for moving save/restore to vcpu_load/put when the host is using SPE is to minimise the host EL2 black-out window. On nVHE we always save/restore in the run loop. For the SPE guest-use-only use-case we can't save/restore in vcpu_load/put - because the guest runs at the same ELx level as the host - and thus doing so would result in the guest tracing part of the host. Though if we determine that (for nVHE systems) the guest SPE is profiling only EL0 - then we could also save/restore in vcpu_load/put where SPE is only being used in the guest. Does that make sense, are my reasons correct? Thanks, Andrew Murray > > > > if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)) > > return; > > @@ -249,19 +246,21 @@ void __hyp_text __debug_restore_host_context(struct kvm_vcpu *vcpu) > > > > void __hyp_text __debug_save_host_context(struct kvm_vcpu *vcpu) > > { > > - /* > > - * Non-VHE: Disable and flush SPE data generation > > - * VHE: The vcpu can run, but it can't hide. > > - */ > > struct kvm_cpu_context *host_ctxt; > > > > host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > - if (!has_vhe()) > > - __debug_save_spe_nvhe(host_ctxt, false); > > + if (cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1), > > + ID_AA64DFR0_PMSVER_SHIFT)) > > + __debug_save_spe_context(host_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > } > > > > void __hyp_text __debug_save_guest_context(struct kvm_vcpu *vcpu) > > { > > + bool kvm_spe_ready = kvm_arm_spe_v1_ready(vcpu); > > + > > + /* SPE present on this vCPU? */ > > + if (kvm_spe_ready) > > + __debug_save_spe_context(&vcpu->arch.ctxt, kvm_spe_ready); > > } > > > > u32 __hyp_text __kvm_get_mdcr_el2(void) > > diff --git a/include/kvm/arm_spe.h b/include/kvm/arm_spe.h > > index 48d118fdb174..30c40b1bc385 100644 > > --- a/include/kvm/arm_spe.h > > +++ b/include/kvm/arm_spe.h > > @@ -16,4 +16,10 @@ struct kvm_spe { > > bool irq_level; > > }; > > > > +#ifdef CONFIG_KVM_ARM_SPE > > +#define kvm_arm_spe_v1_ready(v) ((v)->arch.spe.ready) > > +#else > > +#define kvm_arm_spe_v1_ready(v) (false) > > +#endif /* CONFIG_KVM_ARM_SPE */ > > + > > #endif /* __ASM_ARM_KVM_SPE_H */ > > Thanks, > > M. > -- > Jazz is not dead. It just smells funny... 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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 5826AC33CA4 for ; Fri, 10 Jan 2020 10:54:44 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id CCB282082E for ; Fri, 10 Jan 2020 10:54:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CCB282082E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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 231F64B1D5; Fri, 10 Jan 2020 05:54:43 -0500 (EST) 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 nk0t88Pjcqoc; Fri, 10 Jan 2020 05:54:41 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B2E864B1C7; Fri, 10 Jan 2020 05:54:41 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 1C9F84B1C7 for ; Fri, 10 Jan 2020 05:54:40 -0500 (EST) 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 czzU6lo25usO for ; Fri, 10 Jan 2020 05:54:38 -0500 (EST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id AB9924B1B5 for ; Fri, 10 Jan 2020 05:54:38 -0500 (EST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2A0C2328; Fri, 10 Jan 2020 02:54:38 -0800 (PST) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9E5433F703; Fri, 10 Jan 2020 02:54:37 -0800 (PST) Date: Fri, 10 Jan 2020 10:54:36 +0000 From: Andrew Murray To: Marc Zyngier Subject: Re: [PATCH v2 09/18] arm64: KVM: enable conditional save/restore full SPE profiling buffer controls Message-ID: <20200110105435.GC42593@e119886-lin.cambridge.arm.com> References: <20191220143025.33853-1-andrew.murray@arm.com> <20191220143025.33853-10-andrew.murray@arm.com> <20191221141325.5a177343@why> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191221141325.5a177343@why> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) Cc: kvm@vger.kernel.org, Catalin Marinas , linux-kernel@vger.kernel.org, Sudeep Holla , will@kernel.org, kvmarm , linux-arm-kernel 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 Sat, Dec 21, 2019 at 02:13:25PM +0000, Marc Zyngier wrote: > On Fri, 20 Dec 2019 14:30:16 +0000 > Andrew Murray wrote: > > [somehow managed not to do a reply all, re-sending] > > > From: Sudeep Holla > > > > Now that we can save/restore the full SPE controls, we can enable it > > if SPE is setup and ready to use in KVM. It's supported in KVM only if > > all the CPUs in the system supports SPE. > > > > However to support heterogenous systems, we need to move the check if > > host supports SPE and do a partial save/restore. > > No. Let's just not go down that path. For now, KVM on heterogeneous > systems do not get SPE. If SPE has been enabled on a guest and a CPU > comes up without SPE, this CPU should fail to boot (same as exposing a > feature to userspace). > > > > > Signed-off-by: Sudeep Holla > > Signed-off-by: Andrew Murray > > --- > > arch/arm64/kvm/hyp/debug-sr.c | 33 ++++++++++++++++----------------- > > include/kvm/arm_spe.h | 6 ++++++ > > 2 files changed, 22 insertions(+), 17 deletions(-) > > > > diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c > > index 12429b212a3a..d8d857067e6d 100644 > > --- a/arch/arm64/kvm/hyp/debug-sr.c > > +++ b/arch/arm64/kvm/hyp/debug-sr.c > > @@ -86,18 +86,13 @@ > > } > > > > static void __hyp_text > > -__debug_save_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > +__debug_save_spe_context(struct kvm_cpu_context *ctxt, bool full_ctxt) > > { > > u64 reg; > > > > /* Clear pmscr in case of early return */ > > ctxt->sys_regs[PMSCR_EL1] = 0; > > > > - /* SPE present on this CPU? */ > > - if (!cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1), > > - ID_AA64DFR0_PMSVER_SHIFT)) > > - return; > > - > > /* Yes; is it owned by higher EL? */ > > reg = read_sysreg_s(SYS_PMBIDR_EL1); > > if (reg & BIT(SYS_PMBIDR_EL1_P_SHIFT)) > > @@ -142,7 +137,7 @@ __debug_save_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > } > > > > static void __hyp_text > > -__debug_restore_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > +__debug_restore_spe_context(struct kvm_cpu_context *ctxt, bool full_ctxt) > > { > > if (!ctxt->sys_regs[PMSCR_EL1]) > > return; > > @@ -210,11 +205,14 @@ void __hyp_text __debug_restore_guest_context(struct kvm_vcpu *vcpu) > > struct kvm_guest_debug_arch *host_dbg; > > struct kvm_guest_debug_arch *guest_dbg; > > > > + host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > + guest_ctxt = &vcpu->arch.ctxt; > > + > > + __debug_restore_spe_context(guest_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > + > > if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)) > > return; > > > > - host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > - guest_ctxt = &vcpu->arch.ctxt; > > host_dbg = &vcpu->arch.host_debug_state.regs; > > guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr); > > > > @@ -232,8 +230,7 @@ void __hyp_text __debug_restore_host_context(struct kvm_vcpu *vcpu) > > host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > guest_ctxt = &vcpu->arch.ctxt; > > > > - if (!has_vhe()) > > - __debug_restore_spe_nvhe(host_ctxt, false); > > + __debug_restore_spe_context(host_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > So you now do an unconditional save/restore on the exit path for VHE as > well? Even if the host isn't using the SPE HW? That's not acceptable > as, in most cases, only the host /or/ the guest will use SPE. Here, you > put a measurable overhead on each exit. > > If the host is not using SPE, then the restore/save should happen in > vcpu_load/vcpu_put. Only if the host is using SPE should you do > something in the run loop. Of course, this only applies to VHE and > non-VHE must switch eagerly. > On VHE where SPE is used in the guest only - we save/restore in vcpu_load/put. On VHE where SPE is used in the host only - we save/restore in the run loop. On VHE where SPE is used in guest and host - we save/restore in the run loop. As the guest can't trace EL2 it doesn't matter if we restore guest SPE early in the vcpu_load/put functions. (I assume it doesn't matter that we restore an EL0/EL1 profiling buffer address at this point and enable tracing given that there is nothing to trace until entering the guest). However the reason for moving save/restore to vcpu_load/put when the host is using SPE is to minimise the host EL2 black-out window. On nVHE we always save/restore in the run loop. For the SPE guest-use-only use-case we can't save/restore in vcpu_load/put - because the guest runs at the same ELx level as the host - and thus doing so would result in the guest tracing part of the host. Though if we determine that (for nVHE systems) the guest SPE is profiling only EL0 - then we could also save/restore in vcpu_load/put where SPE is only being used in the guest. Does that make sense, are my reasons correct? Thanks, Andrew Murray > > > > if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)) > > return; > > @@ -249,19 +246,21 @@ void __hyp_text __debug_restore_host_context(struct kvm_vcpu *vcpu) > > > > void __hyp_text __debug_save_host_context(struct kvm_vcpu *vcpu) > > { > > - /* > > - * Non-VHE: Disable and flush SPE data generation > > - * VHE: The vcpu can run, but it can't hide. > > - */ > > struct kvm_cpu_context *host_ctxt; > > > > host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > - if (!has_vhe()) > > - __debug_save_spe_nvhe(host_ctxt, false); > > + if (cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1), > > + ID_AA64DFR0_PMSVER_SHIFT)) > > + __debug_save_spe_context(host_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > } > > > > void __hyp_text __debug_save_guest_context(struct kvm_vcpu *vcpu) > > { > > + bool kvm_spe_ready = kvm_arm_spe_v1_ready(vcpu); > > + > > + /* SPE present on this vCPU? */ > > + if (kvm_spe_ready) > > + __debug_save_spe_context(&vcpu->arch.ctxt, kvm_spe_ready); > > } > > > > u32 __hyp_text __kvm_get_mdcr_el2(void) > > diff --git a/include/kvm/arm_spe.h b/include/kvm/arm_spe.h > > index 48d118fdb174..30c40b1bc385 100644 > > --- a/include/kvm/arm_spe.h > > +++ b/include/kvm/arm_spe.h > > @@ -16,4 +16,10 @@ struct kvm_spe { > > bool irq_level; > > }; > > > > +#ifdef CONFIG_KVM_ARM_SPE > > +#define kvm_arm_spe_v1_ready(v) ((v)->arch.spe.ready) > > +#else > > +#define kvm_arm_spe_v1_ready(v) (false) > > +#endif /* CONFIG_KVM_ARM_SPE */ > > + > > #endif /* __ASM_ARM_KVM_SPE_H */ > > Thanks, > > M. > -- > Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 9E772C33CA3 for ; Fri, 10 Jan 2020 10:54:47 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5FB3D2082E for ; Fri, 10 Jan 2020 10:54:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="AJor8juc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5FB3D2082E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Humfp1VE5pSH9EsqmjXgFmdsd/fO257phW3T+9tAKyQ=; b=AJor8jucLgnBPo jP0m+6zcj7ia7RyK6eaF9gPmOsRrxiBHGPOfrkT14ighj8tAhhdarNeXIDbSqRGj8np24Cj6pkSMb CpIPDUknOywTQ3EMvcYs4jkYw7LNbYznYmnKAXWPlezuYiXhz2/qY+hGwgDmOTXQmsaFMPIDDuqp9 HK29FE+hSotehIluJwf1BZ1mvGv9Wf/Aa6/9ubAHoKq9xyWO8ZJkc4FxwEpGznWKrhFNEGmoHB6Xb pctECFT9bgjRU7RkPpNJHgdswQ/Tq4Tjjk+lenCvhuL2uZUuNXv4B6C+e4J5HDlmz/ptNa03Hmosw 9mn8ioZ7xE6Ut/Pqr5pg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iprw9-0002Rb-Hc; Fri, 10 Jan 2020 10:54:41 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iprw6-0002R5-S1 for linux-arm-kernel@lists.infradead.org; Fri, 10 Jan 2020 10:54:40 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 2A0C2328; Fri, 10 Jan 2020 02:54:38 -0800 (PST) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9E5433F703; Fri, 10 Jan 2020 02:54:37 -0800 (PST) Date: Fri, 10 Jan 2020 10:54:36 +0000 From: Andrew Murray To: Marc Zyngier Subject: Re: [PATCH v2 09/18] arm64: KVM: enable conditional save/restore full SPE profiling buffer controls Message-ID: <20200110105435.GC42593@e119886-lin.cambridge.arm.com> References: <20191220143025.33853-1-andrew.murray@arm.com> <20191220143025.33853-10-andrew.murray@arm.com> <20191221141325.5a177343@why> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20191221141325.5a177343@why> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200110_025438_995003_AB40C3CE X-CRM114-Status: GOOD ( 28.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , kvm@vger.kernel.org, Catalin Marinas , linux-kernel@vger.kernel.org, Sudeep Holla , will@kernel.org, kvmarm , linux-arm-kernel Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, Dec 21, 2019 at 02:13:25PM +0000, Marc Zyngier wrote: > On Fri, 20 Dec 2019 14:30:16 +0000 > Andrew Murray wrote: > > [somehow managed not to do a reply all, re-sending] > > > From: Sudeep Holla > > > > Now that we can save/restore the full SPE controls, we can enable it > > if SPE is setup and ready to use in KVM. It's supported in KVM only if > > all the CPUs in the system supports SPE. > > > > However to support heterogenous systems, we need to move the check if > > host supports SPE and do a partial save/restore. > > No. Let's just not go down that path. For now, KVM on heterogeneous > systems do not get SPE. If SPE has been enabled on a guest and a CPU > comes up without SPE, this CPU should fail to boot (same as exposing a > feature to userspace). > > > > > Signed-off-by: Sudeep Holla > > Signed-off-by: Andrew Murray > > --- > > arch/arm64/kvm/hyp/debug-sr.c | 33 ++++++++++++++++----------------- > > include/kvm/arm_spe.h | 6 ++++++ > > 2 files changed, 22 insertions(+), 17 deletions(-) > > > > diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c > > index 12429b212a3a..d8d857067e6d 100644 > > --- a/arch/arm64/kvm/hyp/debug-sr.c > > +++ b/arch/arm64/kvm/hyp/debug-sr.c > > @@ -86,18 +86,13 @@ > > } > > > > static void __hyp_text > > -__debug_save_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > +__debug_save_spe_context(struct kvm_cpu_context *ctxt, bool full_ctxt) > > { > > u64 reg; > > > > /* Clear pmscr in case of early return */ > > ctxt->sys_regs[PMSCR_EL1] = 0; > > > > - /* SPE present on this CPU? */ > > - if (!cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1), > > - ID_AA64DFR0_PMSVER_SHIFT)) > > - return; > > - > > /* Yes; is it owned by higher EL? */ > > reg = read_sysreg_s(SYS_PMBIDR_EL1); > > if (reg & BIT(SYS_PMBIDR_EL1_P_SHIFT)) > > @@ -142,7 +137,7 @@ __debug_save_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > } > > > > static void __hyp_text > > -__debug_restore_spe_nvhe(struct kvm_cpu_context *ctxt, bool full_ctxt) > > +__debug_restore_spe_context(struct kvm_cpu_context *ctxt, bool full_ctxt) > > { > > if (!ctxt->sys_regs[PMSCR_EL1]) > > return; > > @@ -210,11 +205,14 @@ void __hyp_text __debug_restore_guest_context(struct kvm_vcpu *vcpu) > > struct kvm_guest_debug_arch *host_dbg; > > struct kvm_guest_debug_arch *guest_dbg; > > > > + host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > + guest_ctxt = &vcpu->arch.ctxt; > > + > > + __debug_restore_spe_context(guest_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > + > > if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)) > > return; > > > > - host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > - guest_ctxt = &vcpu->arch.ctxt; > > host_dbg = &vcpu->arch.host_debug_state.regs; > > guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr); > > > > @@ -232,8 +230,7 @@ void __hyp_text __debug_restore_host_context(struct kvm_vcpu *vcpu) > > host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > guest_ctxt = &vcpu->arch.ctxt; > > > > - if (!has_vhe()) > > - __debug_restore_spe_nvhe(host_ctxt, false); > > + __debug_restore_spe_context(host_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > So you now do an unconditional save/restore on the exit path for VHE as > well? Even if the host isn't using the SPE HW? That's not acceptable > as, in most cases, only the host /or/ the guest will use SPE. Here, you > put a measurable overhead on each exit. > > If the host is not using SPE, then the restore/save should happen in > vcpu_load/vcpu_put. Only if the host is using SPE should you do > something in the run loop. Of course, this only applies to VHE and > non-VHE must switch eagerly. > On VHE where SPE is used in the guest only - we save/restore in vcpu_load/put. On VHE where SPE is used in the host only - we save/restore in the run loop. On VHE where SPE is used in guest and host - we save/restore in the run loop. As the guest can't trace EL2 it doesn't matter if we restore guest SPE early in the vcpu_load/put functions. (I assume it doesn't matter that we restore an EL0/EL1 profiling buffer address at this point and enable tracing given that there is nothing to trace until entering the guest). However the reason for moving save/restore to vcpu_load/put when the host is using SPE is to minimise the host EL2 black-out window. On nVHE we always save/restore in the run loop. For the SPE guest-use-only use-case we can't save/restore in vcpu_load/put - because the guest runs at the same ELx level as the host - and thus doing so would result in the guest tracing part of the host. Though if we determine that (for nVHE systems) the guest SPE is profiling only EL0 - then we could also save/restore in vcpu_load/put where SPE is only being used in the guest. Does that make sense, are my reasons correct? Thanks, Andrew Murray > > > > if (!(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY)) > > return; > > @@ -249,19 +246,21 @@ void __hyp_text __debug_restore_host_context(struct kvm_vcpu *vcpu) > > > > void __hyp_text __debug_save_host_context(struct kvm_vcpu *vcpu) > > { > > - /* > > - * Non-VHE: Disable and flush SPE data generation > > - * VHE: The vcpu can run, but it can't hide. > > - */ > > struct kvm_cpu_context *host_ctxt; > > > > host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); > > - if (!has_vhe()) > > - __debug_save_spe_nvhe(host_ctxt, false); > > + if (cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1), > > + ID_AA64DFR0_PMSVER_SHIFT)) > > + __debug_save_spe_context(host_ctxt, kvm_arm_spe_v1_ready(vcpu)); > > } > > > > void __hyp_text __debug_save_guest_context(struct kvm_vcpu *vcpu) > > { > > + bool kvm_spe_ready = kvm_arm_spe_v1_ready(vcpu); > > + > > + /* SPE present on this vCPU? */ > > + if (kvm_spe_ready) > > + __debug_save_spe_context(&vcpu->arch.ctxt, kvm_spe_ready); > > } > > > > u32 __hyp_text __kvm_get_mdcr_el2(void) > > diff --git a/include/kvm/arm_spe.h b/include/kvm/arm_spe.h > > index 48d118fdb174..30c40b1bc385 100644 > > --- a/include/kvm/arm_spe.h > > +++ b/include/kvm/arm_spe.h > > @@ -16,4 +16,10 @@ struct kvm_spe { > > bool irq_level; > > }; > > > > +#ifdef CONFIG_KVM_ARM_SPE > > +#define kvm_arm_spe_v1_ready(v) ((v)->arch.spe.ready) > > +#else > > +#define kvm_arm_spe_v1_ready(v) (false) > > +#endif /* CONFIG_KVM_ARM_SPE */ > > + > > #endif /* __ASM_ARM_KVM_SPE_H */ > > Thanks, > > M. > -- > Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel