From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 6E94242EECC; Thu, 5 Feb 2026 16:01:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770307261; cv=none; b=c2IF1r5NQfGEY3jGy9PcLhF0xaoX2mrOvFiZVKP5tqxwFetAEZYD3nklMweF83Hk9CbWO61ZnDJHn+ijW1ntcvAyFxSuinh9Uoma3DKfcqqXzcJVxxCVOUkYmxBImBIZYo0kmDFgIT1ePwDOrWHKgjDLxyngVycsFIesdPgDhBI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770307261; c=relaxed/simple; bh=r9Yuf71TUcYKqUYaYV0MLO9h0hwdLoZTaCgO+0DE0yM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lrlM4dyNKuixrCEG656vZrTUsBmzM21w9eF3wDwPl8rPH5owM6dIJh987otXs4NcWN2V5Gp2NlIefyezS5UML722uoe8/vXZXYLi5Qt4qb9dzcNHBq/z5sGLJWnSwG5HJJn7DjF63EWlFdemDqXYiziJwkflQbr3gn93YbwVW3s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=s/WyEK/L; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="s/WyEK/L" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F22B8C4CEF7; Thu, 5 Feb 2026 16:00:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1770307261; bh=r9Yuf71TUcYKqUYaYV0MLO9h0hwdLoZTaCgO+0DE0yM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s/WyEK/Lc1S1aKKJFo3THZVJHM2JxrUzAGWEbnhrkFNBS534OF5/r/7yYE9H26C9t ngtTG+Uz7lWk0HGSvCE1O3MeG7Bvz5hp9c86u7JpWRXV4q+OC3vmOC3g0AXn642Iyw 5ZxDr46HpEFRm5tfLPeO8rBiXX28pCbJzmM+MDvI= Date: Thu, 5 Feb 2026 17:00:57 +0100 From: Greg KH To: Sean Christopherson Cc: "Nikunj A. Dadhania" , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, bp@alien8.de, thomas.lendacky@amd.com, tglx@kernel.org, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, xin@zytor.com, pbonzini@redhat.com, x86@kernel.org, jon.grimm@amd.com, stable@vger.kernel.org Subject: Re: [PATCH] x86/fred: Fix early boot failures on SEV-ES/SNP guests Message-ID: <2026020511-filth-promotion-8727@gregkh> References: <20260205051030.1225975-1-nikunj@amd.com> <2026020559-igloo-revolver-1442@gregkh> <59781811-a98b-4289-89e4-58e8247241f8@amd.com> <2026020546-wrongness-duplex-bccd@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Feb 05, 2026 at 07:50:09AM -0800, Sean Christopherson wrote: > On Thu, Feb 05, 2026, Greg KH wrote: > > On Thu, Feb 05, 2026 at 11:40:11AM +0530, Nikunj A. Dadhania wrote: > > > > > > > > > On 2/5/2026 11:25 AM, Greg KH wrote: > > > > On Thu, Feb 05, 2026 at 05:10:30AM +0000, Nikunj A Dadhania wrote: > > > >> FRED enabled SEV-ES and SNP guests fail to boot due to the following > > > >> issues in the early boot sequence: > > > >> > > > >> * FRED does not have a #VC exception handler in the dispatch logic > > > >> > > > >> * For secondary CPUs, FRED is enabled before setting up the FRED MSRs, and > > > >> console output triggers a #VC which cannot be handled > > > >> > > > >> * Early FRED #VC exceptions should use boot_ghcb until per-CPU GHCBs are > > > >> initialized > > > >> > > > >> Fix these issues to ensure SEV-ES/SNP guests can handle #VC exceptions > > > >> correctly during early boot when FRED is enabled. > > > >> > > > >> Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code") > > > >> Cc: stable@vger.kernel.org # 6.9+ > > > >> Signed-off-by: Nikunj A Dadhania > > > >> --- > > > >> > > > >> Reason to add stable tag: > > > >> > > > >> With FRED support for SVM here > > > >> https://lore.kernel.org/kvm/20260129063653.3553076-1-shivansh.dhiman@amd.com, > > > >> SVM and SEV guests running 6.9 and later kernels will support FRED. > > > >> However, *SEV-ES and SNP guests cannot support FRED* and will fail to boot > > > >> with the following error: > > > >> > > > >> [ 0.005144] Using GB pages for direct mapping > > > >> [ 0.008402] Initialize FRED on CPU0 > > > >> qemu-system-x86_64: cpus are not resettable, terminating > > > >> > > > >> Three problems were identified as detailed in the commit message above and > > > >> is fixed with this patch. > > > >> > > > >> I would like the patch to be backported to the LTS kernels (6.12 and 6.18) to > > > >> ensure SEV-ES and SNP guests running these stable kernel versions can boot > > > >> with FRED enabled on FRED-enabled hypervisors. > > > > > > > > That sounds like new hardware support, if you really want that, why not > > > > just use newer kernel versions with this fix in it? Obviously no one is > > > > running those kernels on that hardware today, so this isn't a regression :) > > I disagree, this absolutely is a regression. Kernels without commit 14619d912b65 > will boot on this "new" hardware, kernels with the commit will not. That commit added the new FRED feature, which "broke" when it hits real hardware. Not really a "regression" in my opinion as obviously it never worked at all :) Anyway, I'll let you x86 maintainers here hash that out, just my thoughts... thanks, greg k-h