From nobody Thu May 14 08:24:47 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E809C433FE for ; Tue, 12 Apr 2022 20:05:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231313AbiDLUIF (ORCPT ); Tue, 12 Apr 2022 16:08:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231829AbiDLUHW (ORCPT ); Tue, 12 Apr 2022 16:07:22 -0400 Received: from mail-wm1-x349.google.com (mail-wm1-x349.google.com [IPv6:2a00:1450:4864:20::349]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0049CBF8 for ; Tue, 12 Apr 2022 12:59:11 -0700 (PDT) Received: by mail-wm1-x349.google.com with SMTP id l41-20020a05600c1d2900b0038ec007ac7fso1700387wms.4 for ; Tue, 12 Apr 2022 12:59:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=reply-to:date:in-reply-to:message-id:mime-version:references :subject:from:cc; bh=syoYrG4G6wc/D9QpXxmJ5xqKPPyBOCzpGpn970RrPGk=; b=AzIAUSbC0HT1iPMFN81vdTHOeJ5CmdCGjCiwRGHENOURvCjSrPoZVBFIa00KT0UXk+ Or3fgc9coJ7lNzQAc0ddVYnjGwFjDclwLFYllf98AUzuBWt16G57jAs/N8M0J7g9LPUu mWMeztpx/ZjRmxCCF2R3ibegnY9anVUyLrSu7m+rwcfbr/hSyS4CVx/LPGNjYUvrDkjh q6wpWRociYBSPlAKBwcqnhAPA1SqU57/6CZxe1mG1jX+IsybNjU21kfS6xE4al9aUgV1 mBbGLI4OxFdiSGcFcC8DwVKCSALMD7SWm0N39L/VRN6IySmXhldp2j0kk/owvCDLgcL8 mEOg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:reply-to:date:in-reply-to:message-id :mime-version:references:subject:from:cc; bh=syoYrG4G6wc/D9QpXxmJ5xqKPPyBOCzpGpn970RrPGk=; b=vSG1UwmmtyRnWVo+B122CBNP26IaIlPkg11cwXY6mllXAbMeAlzyvDBMz7lvPlMkPa LbU4OrIEMBZpZcbcT8/IcbWU0Ac/qDuV4q2q34cjXFGDMgONDAn3ERSJAeZblEzZZ9o8 vKdTLvHj0Bx9fK+2+HNLHID84XACUEi939IiqMKuuu6ITjpy4GBGAea2A3QiGchXbYqk 3d32z9cv6QrThYt0O87QAtre2omudi4qxYkAb/32HWgBJubO9WKMekVG5s/DMbUCvb7Y s3fwhpgSGLDLPjgzCVAxgXujQT0csqHL4Rj3fhhyYEYZGhO/2ERG9SVSvqRl88vk4paX B4DQ== X-Gm-Message-State: AOAM533erMTviGM7UPHJDqcZIJQmcAOKGDvBMqOMky6gbXgbK3IPan8p mmJnps1FJ68dUUXn0jLY7GJEUj+XB+Hc X-Google-Smtp-Source: ABdhPJz4RtEBFxR8dOWxNhwT5sJYg2f8+ScFUMpOLlbygiH0VMVqy9v9t961e6WlRx11zKc7fmqhPYqLSwZT X-Received: from zhanwei.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2da8]) (user=zhanwei job=sendgmr) by 2002:a7b:c186:0:b0:38e:c0de:36b6 with SMTP id y6-20020a7bc186000000b0038ec0de36b6mr5724019wmi.53.1649793545148; Tue, 12 Apr 2022 12:59:05 -0700 (PDT) Reply-To: Wei Zhang Date: Tue, 12 Apr 2022 19:58:45 +0000 In-Reply-To: <20220412195846.3692374-1-zhanwei@google.com> Message-Id: <20220412195846.3692374-2-zhanwei@google.com> Mime-Version: 1.0 References: <20220412195846.3692374-1-zhanwei@google.com> X-Mailer: git-send-email 2.35.1.1178.g4f1659d476-goog Subject: [PATCH 1/2] KVM: x86: allow guest to send its _stext for kvm profiling From: Wei Zhang Cc: Wei Zhang , Suleiman Souhlal , Sangwhan Moon , Ingo Molnar , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The profiling buffer is indexed by (pc - _stext) in do_profile_hits(), which doesn't work for KVM profiling because the pc represents an address in the guest kernel. readprofile is broken in this case, unless the guest kernel happens to have the same _stext as the host kernel. This patch adds a new hypercall so guests could send its _stext to the host, which will then be used to adjust the calculation for KVM profiling. Signed-off-by: Wei Zhang --- arch/x86/kvm/x86.c | 15 +++++++++++++++ include/linux/kvm_host.h | 4 ++++ include/uapi/linux/kvm_para.h | 1 + virt/kvm/Kconfig | 5 +++++ 4 files changed, 25 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 547ba00ef64f..abeacdd5d362 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9246,6 +9246,12 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) vcpu->arch.complete_userspace_io =3D complete_hypercall_exit; return 0; } +#ifdef CONFIG_ACCURATE_KVM_PROFILING + case KVM_HC_GUEST_STEXT: + vcpu->kvm->guest_stext =3D a0; + ret =3D 0; + break; +#endif default: ret =3D -KVM_ENOSYS; break; @@ -10261,6 +10267,15 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) */ if (unlikely(prof_on =3D=3D KVM_PROFILING)) { unsigned long rip =3D kvm_rip_read(vcpu); +#ifdef CONFIG_ACCURATE_KVM_PROFILING + /* + * Profiling buffer is indexed by (rip - _stext), but it's + * supposed to be indexed by (rip - guest_stext) instead. + * Therefore apply an offest in advance to get correct results. + */ + if (vcpu->kvm->guest_stext) + rip +=3D (unsigned long)_stext - vcpu->kvm->guest_stext; +#endif profile_hit(KVM_PROFILING, (void *)rip); } =20 diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 3f9b22c4983a..65caaa4d87c4 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -781,6 +781,10 @@ struct kvm { struct notifier_block pm_notifier; #endif char stats_id[KVM_STATS_NAME_SIZE]; + +#ifdef CONFIG_ACCURATE_KVM_PROFILING + unsigned long guest_stext; +#endif }; =20 #define kvm_err(fmt, ...) \ diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h index 960c7e93d1a9..dcb4ba1f033c 100644 --- a/include/uapi/linux/kvm_para.h +++ b/include/uapi/linux/kvm_para.h @@ -30,6 +30,7 @@ #define KVM_HC_SEND_IPI 10 #define KVM_HC_SCHED_YIELD 11 #define KVM_HC_MAP_GPA_RANGE 12 +#define KVM_HC_GUEST_STEXT 13 =20 /* * hypercalls use architecture specific diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index a8c5c9f06b3c..8798f75ddade 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -72,3 +72,8 @@ config KVM_XFER_TO_GUEST_WORK =20 config HAVE_KVM_PM_NOTIFIER bool + +# Offer an additional hypercall to a guest so it could pass value of _stex= t to +# host, which will be used to adjust the calculation of KVM profiling. +config ACCURATE_KVM_PROFILING + bool --=20 2.35.1.1178.g4f1659d476-goog From nobody Thu May 14 08:24:47 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22B6FC433F5 for ; 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Tue, 12 Apr 2022 12:59:07 -0700 (PDT) Reply-To: Wei Zhang Date: Tue, 12 Apr 2022 19:58:46 +0000 In-Reply-To: <20220412195846.3692374-1-zhanwei@google.com> Message-Id: <20220412195846.3692374-3-zhanwei@google.com> Mime-Version: 1.0 References: <20220412195846.3692374-1-zhanwei@google.com> X-Mailer: git-send-email 2.35.1.1178.g4f1659d476-goog Subject: [PATCH 2/2] KVM: x86: illustrative example for sending guest _stext with a hypercall From: Wei Zhang Cc: Wei Zhang , Suleiman Souhlal , Sangwhan Moon , Ingo Molnar , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A guest could send its _stext with the newly added hypercall. The statistics collected afterwards will be correct in the kernel. Signed-off-by: Wei Zhang --- arch/x86/kernel/setup.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index c95b9ac5a457..ee8c4fd4efe9 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -24,6 +24,7 @@ #include #include =20 +#include #include =20 #include @@ -1241,6 +1242,11 @@ void __init setup_arch(char **cmdline_p) #endif =20 unwind_init(); + + /* + * Send the _stext to the host kernel. + */ + kvm_hypercall1(KVM_HC_GUEST_STEXT, (unsigned long)_stext); } =20 #ifdef CONFIG_X86_32 --=20 2.35.1.1178.g4f1659d476-goog