From patchwork Thu Apr 21 05:12:44 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxim Levitsky X-Patchwork-Id: 12821105 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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D28C3C433F5 for ; Thu, 21 Apr 2022 05:13:58 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B6C0C10F37F; Thu, 21 Apr 2022 05:13:57 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id 5C0EA10F387 for ; Thu, 21 Apr 2022 05:13:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650518035; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TE0/IyhbX+PJJtmqWsYqEi/mVebhKn0u1Uz64oTynUA=; b=ga47WoLeZCY8SIQ6L9SL4GA1sItR4l8Tr6jhduHspe/tifhPuoXSDfavwet5h1yeW63FW0 NQpsB5Psc4GdqcAMNzJyQmJiRMq6kzmKGOr2PMRFdMHPxI0wI9conLFHPjP69ff+TebMZx 8Zz36HknXcgJgh5T6tc2Yctt7raquUo= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-212-BwterifsOBidoQRuIu9gkQ-1; Thu, 21 Apr 2022 01:13:50 -0400 X-MC-Unique: BwterifsOBidoQRuIu9gkQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5DC1A80005D; Thu, 21 Apr 2022 05:13:49 +0000 (UTC) Received: from localhost.localdomain (unknown [10.40.194.231]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0CEB1145BA5A; Thu, 21 Apr 2022 05:13:43 +0000 (UTC) From: Maxim Levitsky To: kvm@vger.kernel.org Subject: [RFC PATCH v2 10/10] KVM: SVM: allow to avoid not needed updates to is_running Date: Thu, 21 Apr 2022 08:12:44 +0300 Message-Id: <20220421051244.187733-11-mlevitsk@redhat.com> In-Reply-To: <20220421051244.187733-1-mlevitsk@redhat.com> References: <20220421051244.187733-1-mlevitsk@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.7 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Wanpeng Li , David Airlie , dri-devel@lists.freedesktop.org, "H. Peter Anvin" , Joerg Roedel , x86@kernel.org, Maxim Levitsky , Ingo Molnar , Zhi Wang , Dave Hansen , intel-gfx@lists.freedesktop.org, Borislav Petkov , Rodrigo Vivi , Thomas Gleixner , intel-gvt-dev@lists.freedesktop.org, Jim Mattson , Tvrtko Ursulin , Sean Christopherson , linux-kernel@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Allow optionally to make KVM not update is_running unless it is functionally needed which is only when a vCPU halts, or is in the guest mode. This means security wise that if a vCPU is scheduled out, other vCPUs could still send doorbell messages to the last physical CPU where this vCPU was last running. If a malicious guest tries to do it can slow down the victim CPU by about 40% in my testing, so this should only be enabled if physical CPUs are not shared among guests. The option is avic_doorbell_strict and is true by default, setting it to false allows this relaxed non strict mode. Signed-off-by: Maxim Levitsky --- arch/x86/kvm/svm/avic.c | 19 ++++++++++++------- arch/x86/kvm/svm/svm.c | 19 ++++++++++++++----- arch/x86/kvm/svm/svm.h | 1 + 3 files changed, 27 insertions(+), 12 deletions(-) diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index 9176c35662ada..1bfe58ee961b2 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -1641,7 +1641,7 @@ avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu, bool r) void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { - u64 entry; + u64 old_entry, new_entry; int h_physical_id = kvm_cpu_get_apicid(cpu); struct vcpu_svm *svm = to_svm(vcpu); @@ -1660,14 +1660,16 @@ void __avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) if (kvm_vcpu_is_blocking(vcpu)) return; - entry = READ_ONCE(*(svm->avic_physical_id_cache)); - WARN_ON(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK); + old_entry = READ_ONCE(*(svm->avic_physical_id_cache)); + new_entry = old_entry; - entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK; - entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK); - entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK; + new_entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK; + new_entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK); + new_entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK; + + if (old_entry != new_entry) + WRITE_ONCE(*(svm->avic_physical_id_cache), new_entry); - WRITE_ONCE(*(svm->avic_physical_id_cache), entry); avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, true); } @@ -1777,6 +1779,9 @@ void avic_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu) void avic_vcpu_blocking(struct kvm_vcpu *vcpu) { + if (!avic_doorbell_strict) + __nested_avic_put(vcpu); + if (!kvm_vcpu_apicv_active(vcpu)) return; diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 3d9ab1e7b2b52..7e79fefc81650 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -190,6 +190,10 @@ module_param(avic, bool, 0444); static bool force_avic; module_param_unsafe(force_avic, bool, 0444); +bool avic_doorbell_strict = true; +module_param(avic_doorbell_strict, bool, 0444); + + bool __read_mostly dump_invalid_vmcb; module_param(dump_invalid_vmcb, bool, 0644); @@ -1395,16 +1399,21 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu) if (kvm_vcpu_apicv_active(vcpu)) __avic_vcpu_load(vcpu, cpu); - __nested_avic_load(vcpu, cpu); } static void svm_vcpu_put(struct kvm_vcpu *vcpu) { - if (kvm_vcpu_apicv_active(vcpu)) - __avic_vcpu_put(vcpu); - - __nested_avic_put(vcpu); + /* + * Forbid AVIC's peers to send interrupts + * to this CPU unless we are in non strict mode, + * in which case, we will do so only when this vCPU blocks + */ + if (avic_doorbell_strict) { + if (kvm_vcpu_apicv_active(vcpu)) + __avic_vcpu_put(vcpu); + __nested_avic_put(vcpu); + } svm_prepare_host_switch(vcpu); diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index 7d1a5028750e6..7139bbb534f9e 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -36,6 +36,7 @@ extern u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly; extern bool npt_enabled; extern int vgif; extern bool intercept_smi; +extern bool avic_doorbell_strict; /* * Clean bits in VMCB.