From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x225OO1msehJdDVMHgyJB+mLjlV3PQ5OcYmBjDNrOTpIgL7Mh3Nv9VgT7UlbJXSEzFtL/yVw0 ARC-Seal: i=1; a=rsa-sha256; t=1516989551; cv=none; d=google.com; s=arc-20160816; b=oKsbstCZ2MmUv6vKoSDgwHwVxp16Iipd1XE3erCYnB+S5edIPR6PZhxHqoCR+/LNPZ 6oRipH92Hhsyd7zXZq7Z9bdRiSjJo8kwj9fylgY9qRzzHyRv3edptU7VJr7j0Iwp+THT bW+dVC8+p1+Ux9Hf699gN9uTTYIpxFKn/A/uEn5heMZps4hHLRPJZ0RC386wbBiu++D2 vGXGkQGtqHNWWpm0bXcvvVQMWDoUjG32l636kb4EiWufajiRL+lYsVgacX+qgBETrNJB w/XLKCIm7yvMPpqDHexzL9CiEMS6B7zBvkK7vzct220zrroPjoA/cJUUPfTZo7Yeb4Wr wvaw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:arc-authentication-results; bh=7hXr9Y62FdgpuznM55OkLVWUmDsLki4A9crw6G/cQJY=; b=F8o7UOvTtu8niDtewnMA+U59I9uwQKR0Q3xtoBl1rmp56J5LvUXehj75XQQmjTomQ2 H/HFoJYYn9fWHXZF4BOMZabRWujuqfnNd+YgS8BWSv18bE1d+sJBGW/1pOxD0SXTJW/7 vo6KN0SoEc5JVfCVX1Ux7XGWCebGBNIXzeqL4abXbxpRA6g2bJw8qWZHhF7n2ImgW7rm lENdOc7Z36H7GivfHq29hmdfSu4F7BrCyW+adyV7YhIA75Dc4thoEL0ZQX/2OitfLGYP mwW14qn4M0BbrvjNEbvt+2pevX01Jfk935UWf9VYU4fqucx8jVZGMC2GbmPH0WQjqHav QpYg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of ak@linux.intel.com designates 192.55.52.93 as permitted sender) smtp.mailfrom=ak@linux.intel.com Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of ak@linux.intel.com designates 192.55.52.93 as permitted sender) smtp.mailfrom=ak@linux.intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,417,1511856000"; d="scan'208";a="13388641" Date: Fri, 26 Jan 2018 09:59:01 -0800 From: Andi Kleen To: Linus Torvalds Cc: David Woodhouse , Dave Hansen , Liran Alon , Laura Abbott , Andrew Lutomirski , Janakarajan Natarajan , Borislav Petkov , "Mallick, Asit K" , Radim =?utf-8?B?S3LEjW3DocWZ?= , KarimAllah Ahmed , Peter Anvin , Jun Nakajima , Ingo Molnar , the arch/x86 maintainers , Ashok Raj , "Van De Ven, Arjan" , Tim Chen , Paolo Bonzini , Linux Kernel Mailing List , Peter Zijlstra , Thomas Gleixner , Greg Kroah-Hartman , Masami Hiramatsu , Arjan van de Ven , Tom Lendacky , Dan Williams , Joerg Roedel , Andrea Arcangeli , KVM list Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation Message-ID: <20180126175901.GL26209@tassilo.jf.intel.com> References: <7c0b0879-3448-43e4-8380-4708fc787113@default> <50c5d627-8975-184b-b50f-4cc02c5816c5@intel.com> <1516957886.30244.161.camel@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590140582166248265?= X-GMAIL-MSGID: =?utf-8?q?1590678835925901472?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Fri, Jan 26, 2018 at 09:19:09AM -0800, Linus Torvalds wrote: > On Fri, Jan 26, 2018 at 1:11 AM, David Woodhouse wrote: > > > > Do we need to look again at the fact that we've disabled the RSB- > > stuffing for SMEP? > > Absolutely. SMEP helps make people a lot less worried about things, > but it doesn't fix the "BTB only contains partial addresses" case. > > But did we do that "disable stuffing with SMEP"? I'm not seeing it. In > my tree, it's only conditional on X86_FEATURE_RETPOLINE. For Skylake we need RSB stuffing even with SMEP to avoid falling back to the BTB on underflow. It's also always needed with virtualization. -Andi From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation Date: Fri, 26 Jan 2018 09:59:01 -0800 Message-ID: <20180126175901.GL26209@tassilo.jf.intel.com> References: <7c0b0879-3448-43e4-8380-4708fc787113@default> <50c5d627-8975-184b-b50f-4cc02c5816c5@intel.com> <1516957886.30244.161.camel@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Woodhouse , Dave Hansen , Liran Alon , Laura Abbott , Andrew Lutomirski , Janakarajan Natarajan , Borislav Petkov , "Mallick, Asit K" , Radim =?utf-8?B?S3LEjW3DocWZ?= , KarimAllah Ahmed , Peter Anvin , Jun Nakajima , Ingo Molnar , the arch/x86 maintainers , Ashok Raj , "Van De Ven, Arjan" , Tim Chen , Paolo Bonzini , Linux Kernel Mailing List Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, Jan 26, 2018 at 09:19:09AM -0800, Linus Torvalds wrote: > On Fri, Jan 26, 2018 at 1:11 AM, David Woodhouse wrote: > > > > Do we need to look again at the fact that we've disabled the RSB- > > stuffing for SMEP? > > Absolutely. SMEP helps make people a lot less worried about things, > but it doesn't fix the "BTB only contains partial addresses" case. > > But did we do that "disable stuffing with SMEP"? I'm not seeing it. In > my tree, it's only conditional on X86_FEATURE_RETPOLINE. For Skylake we need RSB stuffing even with SMEP to avoid falling back to the BTB on underflow. It's also always needed with virtualization. -Andi