From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DA9EA391E73 for ; Mon, 27 Jul 2026 15:27:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785166042; cv=none; b=EU2vjc9vLRB2HUXcSlVX3HXIT+IWBp5AYUQtuCNW/l1xDNkacVdB9lf+OdtgKVuxqcMRlSkCLjmz8wEr86ceDp5qBIFrY67EvNrl4qmppKj6O4HI11DOJXuOh3IaV1fAV4ZDx0U5TItJ6G4PmpOZLH3tVpai/ONsrwmVC/0XBkk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785166042; c=relaxed/simple; bh=zM3YKYBF5Ow4F/30IYJUSdZG0wFWAxs1rbGMCyNjfBM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=fyrTm5bKx17Bx6A7FvS+kynAtd/4ESHNfB5y022smCNZCWe7xLuSL44Z1emdMrgaDHzg8HfniuOr7rKJcmPod/g/V+XUojk2qotmNQQdLkSidttRohDWOhZKZ+Ihv7J1KlJVEDVh9YLN5af/cBQaFn+JxpUHldXvM+1rjJWWeJE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=N3PUbmRR; arc=none smtp.client-ip=209.85.210.200 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="N3PUbmRR" Received: by mail-pf1-f200.google.com with SMTP id d2e1a72fcca58-84e13b57b2cso4150619b3a.1 for ; Mon, 27 Jul 2026 08:27:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1785166040; x=1785770840; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=1xYjVu2PU5ywM5mcIzPZDkpnujTQinp7QtborFpJrUY=; b=N3PUbmRRSr2R1mU4wJxFWwuGs1v7HhET5YQ9v1WL+WgiUhJti7ECoiLhL+8A3MbOmj vj6Ebs1aVWBquhL0I7dq1woRhs1xfDFyeylaleQlTP5F2/X5e43rAxtk5XVNXdM7A0E6 2go7lAyV2c3s8bw+3usJr4XCJBgXcLSpJIIHbRzRJ/OZJb+//krTVRwdO2v145l4GElu xmi/pkQhGP31YoKhNEDVhGn3yxLbOTo3jQx5qScxUkYkGlu5r49NR89QBKCHdCshHACG 67irhUZatgWjDQkkrP7e9QlmrKY1HO2TbfrivoauFX13CRkjzdB/7rfMCCM4O3LxSMir Ww/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785166040; x=1785770840; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=1xYjVu2PU5ywM5mcIzPZDkpnujTQinp7QtborFpJrUY=; b=oUqggv5HPfYeZ9hTi7L5dSek+dqf9TgS3+U57sFe8o1UNbqUNPuRTbfdEVMkHMBJ/w mFolC/hPosabzCP0JFuDww6se/kLgXHQUU5Qbbt7RRUsRDLJc/Q6uBNbWuZbGb7/VWKf 8qVYlV7LPAZFuudgFpBf/xuwDSW5cJu410w5GAhEv4NgfsJPWPC12LN7A6bU3tTD97NN kOMSPVWs0vWoLBAKMDAAfNeGOOOXIelX1Sod76V53EVeymYqp/jy359vPHwn/fxuve7Z TQIYqdMBJjHZMWKBGqhUHxJjt23fydJZwEaSUvTyWuoRlc7eyTTcX6iJ2s5jD8B1elez vC6g== X-Forwarded-Encrypted: i=1; AHgh+RpIozudlrMaog0RFXB+EYbsJK5LA6PFblTxmqxR8hcJvsy2+ubrE1IrNmUEl8RrTz299aY=@vger.kernel.org X-Gm-Message-State: AOJu0YyizZoiCpDyeA+pGE3G9EWie2QPrp4yxaeq47mFr52F7+hY6CGq +Gtdf0GWXT9F77HhR5vtrPZbkPVqh4HSmI8ka36esxZ4EmSJfp2UTYAQajUDY2kUe1h9fCXrzTY 2uAny1Q== X-Received: from pfbmb2.prod.google.com ([2002:a05:6a00:7602:b0:847:80c0:ec04]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:94ee:b0:847:9367:e054 with SMTP id d2e1a72fcca58-84e88b4bd33mr927497b3a.57.1785166039852; Mon, 27 Jul 2026 08:27:19 -0700 (PDT) Date: Mon, 27 Jul 2026 08:27:19 -0700 In-Reply-To: <52cd5021-0290-401e-85d8-bdff0d07a9f7@intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260720205208.519622-1-chang.seok.bae@intel.com> <52cd5021-0290-401e-85d8-bdff0d07a9f7@intel.com> Message-ID: Subject: Re: [PATCH v2] KVM: x86: Remove AMX-TF32 enumeration From: Sean Christopherson To: "Chang S. Bae" Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, pbonzini@redhat.com, stable@vger.kernel.org, Zhao Liu , Binbin Wu Content-Type: text/plain; charset="us-ascii" On Thu, Jul 23, 2026, Chang S. Bae wrote: > On 7/23/2026 11:04 AM, Sean Christopherson wrote: > > > > I'm not convinced that yanking out support is the right move. By publishing the > > feature, for several years, Intel pretty much burned that CPUID bit. E.g. it's > > not impossible that someone other than Intel has implemented TF32 instructions. > > > > The opcodes are fair game in the future, because their use can be qualified and > > guarded, but the same doesn't hold true for enumeration. E.g. similar to how > > MPX got ripped out and its XSTATE assets got reused for APX, but the CPUID feature > > enumeration is forever reserved for MPX (I hope). > > > > If the argument is that "Intel Architecture Instruction Set Extensions and Future > > Features" isn't binding documentation, i.e. that Intel can do take backs until a > > feature is documented in the SDM, then I honestly don't see any option but to > > refuse to accept new features until they land in the SDM. Which I don't think > > any of us want. > One distinction I could think of is whether a feature ever ships in > implementations. If a feature is actually implemented and is later > deprecated or removed, then I agree the bit should remain reserved. That > appears quite clear. Per Christian, who's mail client apparently doesn't use In-Reply-To and breaks threading for me and lore, TF32 made it into a shipped product[*]. So "officially", NAK. [*] https://lore.kernel.org/all/CAKSQd8V%3DwfVrUxeU%2BfDRgKJBLdiyCkkY2SRY%2BOoRBNE68LFnCg@mail.gmail.com