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 3810B329C6A; Thu, 5 Feb 2026 05:55:43 +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=1770270944; cv=none; b=QihaDCjdFmikwtR1Dm8RI2xXqozXR1NeEsanHp+tl2bAxav/BSHh2+V6tsBwvK1HxH9oP3nvFgVwsYkMSfr6E4c4s6c74ThLmQLoNFqybabpM5buyYQWlEGVzhuQazMQ9eC2s8yYt7UyBC+fPPTAj7FS5+qvGnwWnmIUmQu97Xo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770270944; c=relaxed/simple; bh=zRy/wL8N0ZhtqhVQVpfEU8PWmepu5rLGMPBpQUp+Yek=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LpIVz5RgPKDODVSuX7FTProYu5W1D3lPNwO93UqzfcajGoMW2jwaqO2xhSl6nTwisctj5D24ecv096F/wYB5lAzutFum4gfGR/PNcHv+QPcaIZxEZlh9DEWtGwhqvau7k0PMbIxPsB1j6ywylYzUNEc5w24HljLyw75lJNo/nbE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tFbSevcl; 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="tFbSevcl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 468B8C4CEF7; Thu, 5 Feb 2026 05:55:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1770270943; bh=zRy/wL8N0ZhtqhVQVpfEU8PWmepu5rLGMPBpQUp+Yek=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tFbSevclevupjvbBMW8fXsUJdnp+Qz1/XGimrp1jigfCnsfJHCbs+Bwf9/NUG9v1Q o51nR1LvelENXQ0NsSlKV/CLsPVJ0Zu8+dFfPq9RNsR0WDNCTnmQRJqZ4NRsp8gQmh Oa+y2z0GaxcRLpOCdQKLtJWkmFmYwG4P+83wU6Dg= Date: Thu, 5 Feb 2026 06:55:40 +0100 From: Greg KH To: Nikunj A Dadhania Cc: 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, seanjc@google.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: <2026020559-igloo-revolver-1442@gregkh> References: <20260205051030.1225975-1-nikunj@amd.com> Precedence: bulk X-Mailing-List: stable@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: <20260205051030.1225975-1-nikunj@amd.com> 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 :) thanks, greg k-h