From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (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 3CC623BB9FB; Tue, 20 Jan 2026 09:10:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768900220; cv=none; b=XTnqRk0R2fGCg84d7q6fNVAb3CoMXiujeruJwZZ7ggIBcvhEkL/QvO74TvIEErVOEU6abXVTTd8y4C3q0JiyLGatVRiRIF568NUZItZteMzYaK7OhWCKUDepotS4A5VCwq4JK3a0LAZeLAf2KLJtVXshL8GFerT880t+xjY40I0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768900220; c=relaxed/simple; bh=INWriyqgU8K5z5tavmStfbwrpGA/bQ2dhB63CYeeg+U=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=Ya9W/VKq6IM0H6FavuKAx/OTw3n2Mvtsea2Fl60YV3v4Tx1oSnLnD55hJo/xO6i19goLVqeKaEZYEtbYRSRkFrmT/1kEG/BLfqq1YG2QYUq0qXtXj6Zw9Ce9rkitexo5nZPFgBmTLDuED83f7peBGtFKZw1r5xa0qZ8sm5ixSQM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=DPThlz90; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="DPThlz90" Received: from smtpclient.apple (c-24-130-165-117.hsd1.ca.comcast.net [24.130.165.117]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 60K99blX3564407 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 20 Jan 2026 01:09:38 -0800 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 60K99blX3564407 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025122301; t=1768900179; bh=INWriyqgU8K5z5tavmStfbwrpGA/bQ2dhB63CYeeg+U=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=DPThlz90mXRExrFVls06gcRHiiYwXZRSTUEQYNuOga+6skrbb8DihoaoS4YFodhqz jFhXmhw36tt8Hi8m5ZhdObFoX3QGfyD1y25Z7YRiuwLm3RiiyRgIXonFWT9O/+yC7d pWchnPchIjcexYram0t4JrdGDifmy4CKb/prVFKykH+7v3qFn3IQCGHwkwivqIkHop 9OzfVKzUE9b3mGgCNEQ7dFxDOaw+s5RXcyZm5PnmkTUyoZdTGf6gFKvBM1VFNl4JZk ywmoyC0SsYYax7ZGtiEkQNwagZHo19H6EPk1twXOO+ei0IGkrhaQMzkythMmhvQmTz NWXlhpE3r8bBg== Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.300.41.1.7\)) Subject: Re: [PATCH v9 17/22] KVM: x86: Advertise support for FRED From: Xin Li In-Reply-To: Date: Tue, 20 Jan 2026 01:09:27 -0800 Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, pbonzini@redhat.com, seanjc@google.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, hch@infradead.org, sohil.mehta@intel.com Content-Transfer-Encoding: quoted-printable Message-Id: References: <20251026201911.505204-1-xin@zytor.com> <20251026201911.505204-18-xin@zytor.com> <71F2B269-4D29-4B23-9111-E43CDD09CF13@zytor.com> To: Chao Gao X-Mailer: Apple Mail (2.3864.300.41.1.7) > On Jan 20, 2026, at 12:07=E2=80=AFAM, Chao Gao = wrote: >=20 > On Mon, Jan 19, 2026 at 10:56:29PM -0800, Xin Li wrote: >>=20 >>=20 >>> On Nov 11, 2025, at 11:30=E2=80=AFPM, Chao Gao = wrote: >>>=20 >>> I'm not sure if AMD CPUs support FRED, but just in case, we can = clear FRED >>> i.e., kvm_cpu_cap_clear(X86_FEATURE_FRED) in svm_set_cpu_caps(). >>=20 >> AMD will support FRED, with ISA level compatibility: >>=20 >> = https://www.amd.com/en/blogs/2025/amd-and-intel-celebrate-first-anniversar= y-of-x86-ecosys.html >>=20 >> Thus we don=E2=80=99t need to clear the bit. >=20 > In this case, we need to clear FRED for AMD. >=20 > The concern is that before AMD's FRED KVM support is implemented, FRED = will be > exposed to userspace on AMD FRED-capable hardware. This may cause = issues. Hmm, I think it=E2=80=99s Qemu does that. We have 2 filters, one in Qemu and one in KVM, only both are set a = feature is enabled. What I have missed?=