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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49F43CCA487 for ; Wed, 20 Jul 2022 17:39:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233373AbiGTRjL (ORCPT ); Wed, 20 Jul 2022 13:39:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229716AbiGTRjD (ORCPT ); Wed, 20 Jul 2022 13:39:03 -0400 Received: from mail-pf1-x42b.google.com (mail-pf1-x42b.google.com [IPv6:2607:f8b0:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A98896FA3F for ; Wed, 20 Jul 2022 10:39:02 -0700 (PDT) Received: by mail-pf1-x42b.google.com with SMTP id 17so6751845pfy.0 for ; Wed, 20 Jul 2022 10:39:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=gKIOhejkrq+Q8uuRF6iQnfl7G8p3hbpVdHm8R8aIKko=; b=ajAxf9e0OHyYwpsX9evWazSHyzfB73W7maKkyeCSnXzXmlH15O4GzRs+O0rqWHboM2 xaSFxnpeCt7qFTqMMS9oN6DJX38iQ3RLx0mOmFcZ6U9W7O/mWx8AyfjwXOHOQvL7H0Rz egvk5cESz+hck09fG4WZ1dlpsfjehnzKSqVdX1/DJb5U02Olw7UGzpads16T6KPILxGO CenaOBjFSIR0cZpUdrW+EGMT9UCBoCiLO4KSxZblrHalXsskYd6YWpP7LnebWdv9t/iX xhRAwAd2Rq5rT3mdzf/OSWlc6+6KWG9i+QTp4TaDwBUmH5pha1uY+kjF/vHKb+XNvPMj RA6Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=gKIOhejkrq+Q8uuRF6iQnfl7G8p3hbpVdHm8R8aIKko=; b=KUDyqZK60PLYN4ZA1q2jAzZ9qK1RoMORMpQoGby3x1wWRwoqxbiCXghL4jI1mopF9o 50FdxopNUWlx+4oHfB8jGwZW64xIUYIx2Ac+TJ/jZ31S/K4BjdeaOvDkhYd80D7AzmsO niSwyE+E0I1PNsV8ziDYF75XZxCyVd8KCJR0IlElSgw2Xa+V2FHK5NoLWqFLPe9HVjlc 4dWecjNRe+EocM7IKX59EZAubcr8WCfPGDP9CwMb90QhSbB1II3Y8PqgDE6kZrZ3odfz +0EuKc+PVzxrj3wF2wqkSfWwZ+FZ+GnJRNxfmR0mR/VCDYZRDjfmZWtllZ6W7t8eRPux SoYA== X-Gm-Message-State: AJIora/CTXIiGHxEtCCNmvv7cvuMyUjh3dX0H+/jZKTCcO3WS/BjCy7x VXkg0TNEXb9aoeJFwyrunTmh0Q== X-Google-Smtp-Source: AGRyM1soWPcGGf8fAYVmZHjvcI2IFRbHXUOG1yZwYb5ZKKIs1YZVEFCQitJrLQtIHkL7ysf7SiTTNg== X-Received: by 2002:a05:6a00:2481:b0:52a:d50e:e75e with SMTP id c1-20020a056a00248100b0052ad50ee75emr40449773pfv.43.1658338742013; Wed, 20 Jul 2022 10:39:02 -0700 (PDT) Received: from google.com (123.65.230.35.bc.googleusercontent.com. [35.230.65.123]) by smtp.gmail.com with ESMTPSA id l7-20020a170903120700b0016cd74e5f87sm10433764plh.240.2022.07.20.10.39.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Jul 2022 10:39:01 -0700 (PDT) Date: Wed, 20 Jul 2022 17:38:58 +0000 From: Sean Christopherson To: Chao Gao Cc: Kechen Lu , kvm@vger.kernel.org, pbonzini@redhat.com, vkuznets@redhat.com, somduttar@nvidia.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v3 5/7] KVM: x86: add vCPU scoped toggling for disabled exits Message-ID: References: <20220615011622.136646-1-kechenl@nvidia.com> <20220615011622.136646-6-kechenl@nvidia.com> <20220615024311.GA7808@gao-cwp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220615024311.GA7808@gao-cwp> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 15, 2022, Chao Gao wrote: > >@@ -5980,6 +5987,8 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_event, > > int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > > struct kvm_enable_cap *cap) > > { > >+ struct kvm_vcpu *vcpu; > >+ unsigned long i; > > int r; > > > > if (cap->flags) > >@@ -6036,14 +6045,17 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > > break; > > > > mutex_lock(&kvm->lock); > >- if (kvm->created_vcpus) > >- goto disable_exits_unlock; > >+ if (kvm->created_vcpus) { > >+ kvm_for_each_vcpu(i, vcpu, kvm) { > >+ kvm_ioctl_disable_exits(vcpu->arch, cap->args[0]); > >+ static_call(kvm_x86_update_disabled_exits)(vcpu); > > IMO, this won't work on Intel platforms. It's not safe on AMD either because at best the behavior is non-deterministic if the vCPU is already running in the guest, and at worst could cause explosions, e.g. if hardware doesn't like software modifying in-use VMCB state. > Because, to manipulate a vCPU's VMCS, vcpu_load() should be invoked in > advance to load the VMCS. Alternatively, you can add a request KVM_REQ_XXX > and defer updating VMCS to the next vCPU entry. Definitely use a request, doing vcpu_load() from a KVM-scoped ioctl() would be a mess as KVM would need to acquire the per-vCPU lock for every vCPU.