From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH V2 2/3] perf protect LBR when Intel PT is enabled. Date: Mon, 7 Jul 2014 17:46:35 +0200 Message-ID: <20140707154635.GG19379@twins.programming.kicks-ass.net> References: <1404324855-15166-1-git-send-email-kan.liang@intel.com> <1404324855-15166-2-git-send-email-kan.liang@intel.com> <20140703073321.GU19379@twins.programming.kicks-ass.net> <20140703155237.GQ5714@two.firstfloor.org> <20140703170711.GW19379@twins.programming.kicks-ass.net> <37D7C6CF3E00A74B8858931C1DB2F077014C6431@SHSMSX103.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="eGwqSfc1DN4LzNjY" Cc: Andi Kleen , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" To: "Liang, Kan" Return-path: Content-Disposition: inline In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F077014C6431@SHSMSX103.ccr.corp.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org --eGwqSfc1DN4LzNjY Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jul 07, 2014 at 01:57:16PM +0000, Liang, Kan wrote: > > > This doesn't work, e.g. hardware debuggers can take over at any time. > >=20 > > Tough cookies. Hardware debuggers get to deal with whatever crap they > > cause. >=20 > If so, I think I may discard this patch (2/3). I will resubmit the > other two patches as a patch set to only handle the KVM issue we > found. It checks the access of LBR and extra MSRs at the > initialization time and set the flags. So we just need to check the > flags at runtime and avoid the protection by _safe().=20 Right. > For Intel PT and LBR handling, since the PT codes haven't been > integrated yet, I will try to implement another patch later. The > patch will add flags for LBR and PT. When enabling PT, it checks LBR > flag and update the PT flag. When enabling LBR, it checks PT flag and > update the LBR flag. When disabling LBR/PT, we just update the related > flags. we don't need to add _safe or extra rmsr in fast path.=20 Yeah, should be part of the PT patches. > How do you think? With my brain, much like all primates :-) --eGwqSfc1DN4LzNjY Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJTusDbAAoJEHZH4aRLwOS61mwQAKIZg4aFSKzqWGJEeFi8rSt1 bEznCpg9IDjS3xob5I7uPPV5ph5U9cnqumOUJ9HjiwZ5g+5FRwpMKlvMU04+EvVy nqoY2Z//3gP6x7hhIkhtxZtJzz64JSQXRBCDhvr4cXPnnHDYxhasqZX2JjtR1bf4 4tR3FmdD/zFlrm0VdWFoFIg906dcrI96ZHJj96B5g3zETfj6d/3cT8jn/mG7wYwi QcqDZtnXMXX8iP23C5gM8FU1X24hC0NTtpOACWXpfHZAxS8/Jn8atDV/pzBEEleu 0t8lYshV9Q7A9CvoctB8A4k5Q5AmbTNTQe9acg9BehmJdDCMvO82I5UUmWPPmG+b fAHBmVkP+nDYhKvW0rr6MoipbzcGvBiKd/8G7zH2UEhK7ENEBSaaTRFq9a8GjCUz 3ALPUnQ73hAozEfsNkDLCvpYq4r9qtH97m71XI61k/E7RptDwAEwW4w4gqpmCK9d tWLDGOdv/C5LpLtOhhRJEqSbzgl8ElAqQNfthWV6GMEgPOtoril10ZJaECHkCQ5Z ZcUq/pL18bx6vWoZo8mRyXa8Pr+WXHh3Atu3dfbjQqs/w4vW2959ICc3Lq0ecgm8 82d2hf9avsyubOp8YLfAAvouMPp8np8mfTQA0HZFSI7nyuB68P3ZbYl0aHocNc8n pK4Wo/z7XMigig2oYfwj =nnu7 -----END PGP SIGNATURE----- --eGwqSfc1DN4LzNjY--