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 C4B9D24C06A; Tue, 20 May 2025 14:13:06 +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=1747750387; cv=none; b=WsllXNG31V7tO+x84UU7CiAm9VbgNVxhpIn9ApwYrELqeflN8aZFOi6MFbqm3FpjHrep1EZu+7mxDRYaeiyaAq81baHoFwsnzQFP5N0EuGT1NOwP+xZQ+GCJGSurHxI0H0bDoFBeyy6rvLt3USugZ95EQni/4yl0jzl7evP6ZV4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747750387; c=relaxed/simple; bh=9n8dw9eb+20GuWmjSS7Yp145AHRnH4TAd5VgGo22PGg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=L1rv5yKCzzqU/Qo5SrDlJG7d/Ms+FkThg9zylzl3VTfOuK4bGFHKKBghtO6/AMyeyF7AjgxjVQ0vBLF5kfergsk7AzEq4MtO+VT1daO8VrAp2xaMGQWLSpQwcqzuO8Ma5MH17mqbCqV+s9A43fbYd8aKI4WHd+MgiS+DxFFiAw4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PkkqAnuQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="PkkqAnuQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0E96EC4CEE9; Tue, 20 May 2025 14:13:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1747750386; bh=9n8dw9eb+20GuWmjSS7Yp145AHRnH4TAd5VgGo22PGg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PkkqAnuQDZemhPobQcEFfl1TI/R06HqSZtcwwVMGtCBfVh4bZBi8TTq744KJEOOHO Axh3uE+27/VbanrjgsCg22XTKjfLJS7V6gR8GISr5HXOzo7ocKhXHKMnvYlyH26OJz gphpiW9R9RVxguFCf3zKXLGGcUPLio9Lq76oSnt9fxwong4+ANeheuGKdeIXbaWKJb qS/S6mQl/8kHEjym0qt4t0dnC4TPtfIuf34GKuFz1dqzO6KrWbnQMuaYG6MPMWy3c4 0QnGaAAJrXv8ThzHt3GoKMePT1LEhl7f/ozeS38X7ECJv/6nT+Yto08Jg70ghPrClO 4E00B8DEaEdUw== Date: Tue, 20 May 2025 10:13:04 -0400 From: Sasha Levin To: Sean Christopherson Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Borislav Petkov , tglx@linutronix.de, peterz@infradead.org, jpoimboe@kernel.org, corbet@lwn.net, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, pbonzini@redhat.com, thomas.lendacky@amd.com, mario.limonciello@amd.com, perry.yuan@amd.com, kai.huang@intel.com, xiaoyao.li@intel.com, tony.luck@intel.com, xin3.li@intel.com, kan.liang@linux.intel.com, linux-doc@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH AUTOSEL 6.14 317/642] x86/bugs: KVM: Add support for SRSO_MSR_FIX Message-ID: References: <20250505221419.2672473-1-sashal@kernel.org> <20250505221419.2672473-317-sashal@kernel.org> 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; format=flowed Content-Disposition: inline In-Reply-To: On Mon, May 05, 2025 at 03:37:17PM -0700, Sean Christopherson wrote: >On Mon, May 05, 2025, Sasha Levin wrote: >> From: Borislav Petkov >> >> [ Upstream commit 8442df2b49ed9bcd67833ad4f091d15ac91efd00 ] >> >> Add support for >> >> CPUID Fn8000_0021_EAX[31] (SRSO_MSR_FIX). If this bit is 1, it >> indicates that software may use MSR BP_CFG[BpSpecReduce] to mitigate >> SRSO. >> >> Enable BpSpecReduce to mitigate SRSO across guest/host boundaries. >> >> Switch back to enabling the bit when virtualization is enabled and to >> clear the bit when virtualization is disabled because using a MSR slot >> would clear the bit when the guest is exited and any training the guest >> has done, would potentially influence the host kernel when execution >> enters the kernel and hasn't VMRUN the guest yet. >> >> More detail on the public thread in Link below. >> >> Co-developed-by: Sean Christopherson >> Signed-off-by: Sean Christopherson >> Signed-off-by: Borislav Petkov (AMD) >> Link: https://lore.kernel.org/r/20241202120416.6054-1-bp@kernel.org >> Signed-off-by: Sasha Levin >> --- > >Can we please hold off on this until the fix lands[1]? This version introduces >a very measurable performance regression[2] for non-KVM use cases. Sure, I'll drop it. Thanks! -- Thanks, Sasha