From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.12]) (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 3D2421BDAB5; Wed, 20 Nov 2024 18:12:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732126367; cv=none; b=ZEFWKDxmemknRaSx56XTHcjBPpg56LY0EEqU2zvSLPaFG/anXzX0wQQ7uzQJHHSiDn+ZncTUlpvyvXYPtaHmNKHOU8tvU8+/VOUeFIIssRFd8RKJdzQrnQtgoyzpRi3J+5/vII3mBOTuWDCvYJS4/KMOnNXQESDDxorQn03hpIM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732126367; c=relaxed/simple; bh=ioxxLAUmczTtwoDDSxGkvsdiX6i9vCPHTedkjZs4s1A=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kAWQ6HB76jZ1NKpqLMsZ9fM/I4oqw0zC77rxPC1uM1fEBLXiH5AZp8dX19ia4Bi7LiDM5Bc3ypj3bewLg/T3+iZDsyNzFuQzNQaX3QkeASB6VFwaq9mu/Luw3THkR7dP1esmNs/LYBISnpk+BV/SsKRAzW5TGJbwPbMS2RlE6mU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Dfa99b90; arc=none smtp.client-ip=198.175.65.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Dfa99b90" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1732126366; x=1763662366; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=ioxxLAUmczTtwoDDSxGkvsdiX6i9vCPHTedkjZs4s1A=; b=Dfa99b90qaggY0M4T1cHdDp+mLW8IYv7Ydif0M27OMWnTg7vHECJLW9k XnLrLlPUYswpwx4gooTkasdNaB9ooHspnTwbThrOKKxy5gPlbeS+TxnJr 3il7oHrigsJBBTvrZzlj+1zwNY0KsGxHqZM8oirV23O7LbHbhzGrxOKXO z0HSo1OEISZEUl1TN6aEgvEUMVwLTmBwFaPxHgBfNwhhjPsSuE4gWI1ID 9DZNqaJgxT21S/IifvRWRp0RU2wAF0WQ0GdP5UdVdgFithtFS6SqqH/Nx 2lG3dphwLOHHjihGLNUi7fzIzY9dpC4cSU3so22F9km/AF4asJhFl1YOA Q==; X-CSE-ConnectionGUID: zwVUcXIJSU+WQ47D8ciCZQ== X-CSE-MsgGUID: nexgseX/T/CAR0cfPhjpQA== X-IronPort-AV: E=McAfee;i="6700,10204,11262"; a="43587848" X-IronPort-AV: E=Sophos;i="6.12,170,1728975600"; d="scan'208";a="43587848" Received: from orviesa002.jf.intel.com ([10.64.159.142]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Nov 2024 10:12:46 -0800 X-CSE-ConnectionGUID: MnaaUSTUQzeAUDvKUoogeA== X-CSE-MsgGUID: 6J9o4yNOSt2NIfz72mDnzw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,170,1728975600"; d="scan'208";a="120863679" Received: from abkail-mobl.amr.corp.intel.com (HELO desk) ([10.125.145.31]) by orviesa002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Nov 2024 10:12:45 -0800 Date: Wed, 20 Nov 2024 10:12:38 -0800 From: Pawan Gupta To: Josh Poimboeuf Cc: x86@kernel.org, linux-kernel@vger.kernel.org, amit@kernel.org, kvm@vger.kernel.org, amit.shah@amd.com, thomas.lendacky@amd.com, bp@alien8.de, tglx@linutronix.de, peterz@infradead.org, corbet@lwn.net, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, seanjc@google.com, pbonzini@redhat.com, daniel.sneddon@linux.intel.com, kai.huang@intel.com, sandipan.das@amd.com, boris.ostrovsky@oracle.com, Babu.Moger@amd.com, david.kaplan@amd.com, dwmw@amazon.co.uk, andrew.cooper3@citrix.com Subject: Re: [PATCH 1/2] x86/bugs: Don't fill RSB on VMEXIT with eIBRS+retpoline Message-ID: <20241120181238.n3xwpd6uticlaw4a@desk> References: <2e062b6c142bb3770a0829e2cf21e11e8fb6ae5c.1732087270.git.jpoimboe@kernel.org> 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: <2e062b6c142bb3770a0829e2cf21e11e8fb6ae5c.1732087270.git.jpoimboe@kernel.org> On Tue, Nov 19, 2024 at 11:27:50PM -0800, Josh Poimboeuf wrote: > eIBRS protects against RSB underflow/poisoning attacks. Adding > retpoline to the mix doesn't change that. Retpoline has a balanced > CALL/RET anyway. > > So the current full RSB filling on VMEXIT with eIBRS+retpoline is > overkill. Disable it (or do the VMEXIT_LITE mitigation if needed). > > Suggested-by: Pawan Gupta > Signed-off-by: Josh Poimboeuf Reviewed-by: Pawan Gupta