From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C4A1A199A6 for ; Mon, 30 Oct 2023 17:32:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="IyYlixsi" Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B692E9C for ; Mon, 30 Oct 2023 10:31:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698687117; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=3g1TVhpzsOzzHHVoXez8JAaDO7pX06gUTyU2b4+L2DI=; b=IyYlixsiNWlGKrXB5enn4+dorl8uqg2Mts1Q9YjRWfwNiWp6Sk4VVg7Ma30ySQiMb8I0oN T4h9w8/24va4fKDcRUUrG+U6OPg9LAHU8N6z5NHVwvGVcLUgma6HoG0dzruKFBr5mudWm+ TRXs3yRjBxxXzgzfYOju046hqrWAbMs= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-445-a-SKHrDOOs6iHx6NEzWtlA-1; Mon, 30 Oct 2023 13:31:56 -0400 X-MC-Unique: a-SKHrDOOs6iHx6NEzWtlA-1 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4084001846eso35339735e9.1 for ; Mon, 30 Oct 2023 10:31:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698687115; x=1699291915; h=content-transfer-encoding:in-reply-to:autocrypt:from:references:cc :to:content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=3g1TVhpzsOzzHHVoXez8JAaDO7pX06gUTyU2b4+L2DI=; b=Ra8rhAlyYvuD259t/RMlUL3rJDBqUUy7F/r2nyXe4S7SCIlBdfS3AB0DI/Ud95XjJU 27VTMBe7h4N/9POd0DeWeDKcsEMXEZtB6L9A23vH680BvnKDCD9MUDOEUvr6lqE7ZrdQ I5HLe2Q/qb1OSqIOME2xbYeO/Maa8AnEhGac8+ZzU/ja5ax4a0rWgZtHhGOErn14f/3W PinsoZsBoI2sUFe/+gHLQ+7nenw1mqSM+x9XPupSxQBBK4vcYY7potYWu7QuMicFH5Br DYWnIWK/OYvl59FM/Qy4VfIuRn6lAe8FbTWJQr9j73tuI4ot0SGBtdN/x2nM2dbB9Iqt qwIw== X-Gm-Message-State: AOJu0Yy7M0dbuDnC+DqRTkgRAfUBG+yhyLsUOlRZnsc0PSSgH3OgyQa7 hZy9HIfutJ2XrlMGD6PHEJ6aj+FXly1V7kl1ZdkzX6ijVrJ9DQqTjmCdOYyTENbjpDHURlMB0hc grZUq7RUvVRET1fOKabAepgrJYQ== X-Received: by 2002:a05:600c:3b13:b0:405:3455:567e with SMTP id m19-20020a05600c3b1300b004053455567emr8489628wms.5.1698687115253; Mon, 30 Oct 2023 10:31:55 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFOw2pwrz3emhHHPGzRcEZaKdyXE5ETYrjkl0hP08/axAOlUIY6MyqVTu78CJe3u248QTKzww== X-Received: by 2002:a05:600c:3b13:b0:405:3455:567e with SMTP id m19-20020a05600c3b1300b004053455567emr8489569wms.5.1698687114826; Mon, 30 Oct 2023 10:31:54 -0700 (PDT) Received: from [192.168.1.174] ([151.81.68.207]) by smtp.googlemail.com with ESMTPSA id c5-20020a05600c0a4500b004094d4292aesm449246wmq.18.2023.10.30.10.31.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Oct 2023 10:31:54 -0700 (PDT) Message-ID: <0731604e-8692-4c51-9427-78b4c629f9e9@redhat.com> Date: Mon, 30 Oct 2023 18:31:50 +0100 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 18/35] KVM: x86: "Reset" vcpu->run->exit_reason early in KVM_RUN Content-Language: en-US To: Sean Christopherson , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , =?UTF-8?B?TWlja2HDq2wgU2FsYcO8?= =?UTF-8?Q?n?= , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-19-seanjc@google.com> From: Paolo Bonzini Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: <20231027182217.3615211-19-seanjc@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/27/23 20:22, Sean Christopherson wrote: > Initialize run->exit_reason to KVM_EXIT_UNKNOWN early in KVM_RUN to reduce > the probability of exiting to userspace with a stale run->exit_reason that > *appears* to be valid. > > To support fd-based guest memory (guest memory without a corresponding > userspace virtual address), KVM will exit to userspace for various memory > related errors, which userspace *may* be able to resolve, instead of using > e.g. BUS_MCEERR_AR. And in the more distant future, KVM will also likely > utilize the same functionality to let userspace "intercept" and handle > memory faults when the userspace mapping is missing, i.e. when fast gup() > fails. > > Because many of KVM's internal APIs related to guest memory use '0' to > indicate "success, continue on" and not "exit to userspace", reporting > memory faults/errors to userspace will set run->exit_reason and > corresponding fields in the run structure fields in conjunction with a > a non-zero, negative return code, e.g. -EFAULT or -EHWPOISON. And because > KVM already returns -EFAULT in many paths, there's a relatively high > probability that KVM could return -EFAULT without setting run->exit_reason, > in which case reporting KVM_EXIT_UNKNOWN is much better than reporting > whatever exit reason happened to be in the run structure. > > Note, KVM must wait until after run->immediate_exit is serviced to > sanitize run->exit_reason as KVM's ABI is that run->exit_reason is > preserved across KVM_RUN when run->immediate_exit is true. > > Link: https://lore.kernel.org/all/20230908222905.1321305-1-amoorthy@google.com > Link: https://lore.kernel.org/all/ZFFbwOXZ5uI%2Fgdaf@google.com > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/x86.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index ee3cd8c3c0ef..f41dbb1465a0 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -10963,6 +10963,7 @@ static int vcpu_run(struct kvm_vcpu *vcpu) > { > int r; > > + vcpu->run->exit_reason = KVM_EXIT_UNKNOWN; > vcpu->arch.l1tf_flush_l1d = true; > > for (;;) { Reviewed-by: Paolo Bonzini