From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 DAB3A2C0F97 for ; Thu, 15 Jan 2026 16:12:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768493549; cv=none; b=boOTQi27F54LibFjhz0TA2DVDpt+gN2SU6jrfHOc2mNnPbi3X3qQ0lZJcqiN6WrBBIycrzfNVtN8BAF8NgxEaIq5RdZyzxbDMP0/OOFlkQpxEHIT1FN6On5RFwTYrgAMHm05hYDONdG4nDFzLYUlsxkvRmOzbQkqJwG2CVDru5A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768493549; c=relaxed/simple; bh=RHhCaaRNI/nAzrLA7doEVdluNqjWBfYTZo1IN7DjKzI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JcXoZNTaKnUFoHS0xoUCvJCpj8/hr5dYMz5TvuCsucbu02ATTEnLHVXA2EmiYmNLF+UbeA5rdDW4+HU2zeWimcbLOO+7p7EoJ6SJzsRrhZa+obWa0A/f6DyXiG8NnJ8w7JtjgS4YmNeiBr+ekNYIjV8YGtJYnTWGnpjifBbAEqs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Q60/0w05; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=NBnEoi1k; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Q60/0w05"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="NBnEoi1k" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1768493547; 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=x/ZMu7CdHznH2HdFclgVFTLdKzdbKe1vdypK8PHxHR4=; b=Q60/0w05Nx2aJTlGVUgCbToHFU7YAsORrWa0oQUfZmjz+Liapr+8Y/ZXXoJoM5GD5LUgQM 5Q7uR9k5GHBjOcFzca0IXlWvCcsBG3gOERaayMqAVgoM1hinWOa5W7Dlcky+vjs3w5l81o NB+V60K77V9wi1jO6gwemR7t2IFChSA= Received: from mail-ej1-f69.google.com (mail-ej1-f69.google.com [209.85.218.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-587-j1oe___MNYiix4HHOU6h4w-1; Thu, 15 Jan 2026 11:12:25 -0500 X-MC-Unique: j1oe___MNYiix4HHOU6h4w-1 X-Mimecast-MFC-AGG-ID: j1oe___MNYiix4HHOU6h4w_1768493544 Received: by mail-ej1-f69.google.com with SMTP id a640c23a62f3a-b7ff8a27466so110824166b.3 for ; Thu, 15 Jan 2026 08:12:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1768493544; x=1769098344; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:from:to:cc:subject:date:message-id:reply-to; bh=x/ZMu7CdHznH2HdFclgVFTLdKzdbKe1vdypK8PHxHR4=; b=NBnEoi1kguCa1Ek8nCokqk1nEq5Qw8ftbran239TPZo1Rj9dD/rL1ZbBCVyA+JAPlA 1elKWSDwXaY78Vc8664fVRgw7KssWU1MH1R7i1Jl9FDx+/xua+foNydofbtxEP8iFCxN y/o/v2/hvwNl7C/TUxUlksjp/JqKDtnT6Cj0zB0Ht9zQNynh4aGepUcsbPpGi6teae6Y DrhVHu18WbrCT9VQdt1HEglqm4SWpGTh9t1r5LZOne6VoKNFz5YwxsslUfb/ke5W6VGs PNlbfWbqzBtMvmXJhPybrz802ZdfUKWsYWOJ+Ke6TMoGl3Yha2+q9Hmr0eQ+fOYhOrkC lgAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768493544; x=1769098344; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=x/ZMu7CdHznH2HdFclgVFTLdKzdbKe1vdypK8PHxHR4=; b=fsHk0IVJ0+TWgOue0X0q/wvR7LP3ORcsJfiYAx1WziDWRoHwF7l+R8nH7svl3IpSwc XCEpOawthhoWrADr7yU0SXT+6j+1dXWWRxC9zWcltq5OMUDu+QtqKyIbi8Xhyyre86z7 Y+z4RBigP9c2Fs3orKU1x5Ez0dVXVJVkcMzK5MAc+2n1XE965C44MAD4EG6O3j1pg9Am hnHdfI6ciPUcG7zldxf7GAVIpF0XYKZiAej1/ZUGML2BZEkTzVlmnLfjHYA0N9ccvxXR vQeaRoU0vVzcC5mtUEwcdrCSeHgcRZYafyrUrn53hHzzlTB0rDsVbeIvnimp0iFdkA9+ 02FQ== X-Gm-Message-State: AOJu0YwRdpZqixfujJi/KxJOfbq1URB/cB5OqF06phe4uoND3n4a8eAl z2Ek9zv2YmeQSE0tMoVktC0liQ3rhe2RuDspSqsnB9Lk6p44V2SU1rLxwH4kZ5dOJewNhpP+NH8 0mNG9uOx8IyGC//JYwgIoMCcUMTikVGCT37ihUGN1LgUwbbQvxFK0UBPJvXxW614E/w== X-Gm-Gg: AY/fxX7FaTo2anqxFmi0a626oYS6EnWsc2OmUnFT9n9daH1Zv6J+PKeqnCxGoF/dwtQ Guj8FSVROIZprASl488M5VE0oAznqG0BkQaTSsHiPZc20+NWQYoIIIHkAXvJMuCD7h4l8gaR7yj N4C+VoopHGhHdhS6YoQc1nlHDzd5bwwBh3Jd8h8RSw3ufejXzjkhybM367PWxDXxX6Aemtveu+m oiU2fXYqquXgup/yVq6/XtYL0sgY0iwF560R3lVpgsRdadFolIAgE3LXb1sC1U+OlcapoBS9lCi azUy4Hq9qc7hYjJqBHkZ/p//P34qPzBmbLU548lAqn5f4PcQiYFjyYLaAyA3Zs2F4yMMs35p2Hp ifCNOrpp+YqsM+WHemXZYPZOg6wBwh/HG6BtnoyKR4TR8LLRNW8xFHMCBAfm3IVHFdApUfipJij +7WRc9nPXrInA= X-Received: by 2002:a17:907:1ca5:b0:b77:1233:6f32 with SMTP id a640c23a62f3a-b8792feb14dmr11232566b.48.1768493544150; Thu, 15 Jan 2026 08:12:24 -0800 (PST) X-Received: by 2002:a17:907:1ca5:b0:b77:1233:6f32 with SMTP id a640c23a62f3a-b8792feb14dmr11231266b.48.1768493543711; Thu, 15 Jan 2026 08:12:23 -0800 (PST) Received: from [192.168.1.84] ([93.56.161.93]) by smtp.googlemail.com with ESMTPSA id a640c23a62f3a-b86faa6be37sm1484355966b.36.2026.01.15.08.12.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 15 Jan 2026 08:12:23 -0800 (PST) Message-ID: <43474e30-6a14-4ab1-aa2c-5f079503637d@redhat.com> Date: Thu, 15 Jan 2026 17:12:22 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] x86/fpu: Clear XSTATE_BV[i] in save state whenever XFD[i]=1 To: Dave Hansen , Jim Mattson , Sean Christopherson Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, stable@vger.kernel.org References: <20260101090516.316883-1-pbonzini@redhat.com> <20260101090516.316883-2-pbonzini@redhat.com> <9beb7ca4-7bcf-45f1-aefa-f8e6e8122ede@intel.com> From: Paolo Bonzini Content-Language: en-US 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: <9beb7ca4-7bcf-45f1-aefa-f8e6e8122ede@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/15/26 17:07, Dave Hansen wrote: > On 1/6/26 09:56, Jim Mattson wrote: >> Apologies. You're right. Though Intel is a bit coy, the only way to >> interpret that section of the SDM is to conclude that the AMX state in >> the CPU becomes undefined when XFD[18] is set. > > I'll touch base with the folks that wrote that blurb. I'm a little > nervous to interpret that "software should not..." blurb as a full > architectural DANGER sign partly because it's in a "RECOMMENDATIONS FOR > SYSTEM SOFTWARE" section. > > I'm _sure_ they discussed tying XFD[i] and XINUSE[i] together and there > was a good reason they did not. Is there anything that prevents an SMM handler (or more likely, an SMI transfer monitor) to do an XSAVE/XRSTOR and destroy tile data? Paolo