From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linutronix.de (193.142.43.55:993) by crypto-ml.lab.linutronix.de with IMAP4-SSL for ; 13 Oct 2019 20:06:08 -0000 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]) by Galois.linutronix.de with esmtps (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.80) (envelope-from ) id 1iJk7y-00043k-DD for speck@linutronix.de; Sun, 13 Oct 2019 22:06:07 +0200 Received: from chatham.yeoldevic.com ([81.2.79.67] helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iJk7v-0007DP-TW for speck@linutronix.de; Sun, 13 Oct 2019 21:06:03 +0100 Received: from ben by deadeye with local (Exim 4.92.2) (envelope-from ) id 1iJk7v-0006fe-H7 for speck@linutronix.de; Sun, 13 Oct 2019 21:06:03 +0100 Message-ID: <67b50974c10173d0399025c96dabc53c1a0e6314.camel@decadent.org.uk> Subject: [MODERATED] Re: [PATCH v6 9/9] TAAv6 9 From: Ben Hutchings Date: Sun, 13 Oct 2019 21:05:58 +0100 In-Reply-To: <20191012014102.GA22297@guptapadev.amr> References: <5d9e6f13.1c69fb81.d7036.be99SMTPIN_ADDED_BROKEN@mx.google.com> <20191010065412.GD256999@kroah.com> <20191012014102.GA22297@guptapadev.amr> MIME-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-qmj1DIwVA5INE4TQwFo0" To: speck@linutronix.de List-ID: --=-qmj1DIwVA5INE4TQwFo0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2019-10-11 at 18:41 -0700, speck for Pawan Gupta wrote: > On Thu, Oct 10, 2019 at 08:54:12AM +0200, speck for Greg KH wrote: [...] > > > +/* Take tsx_mutex lock and update tsx_ctrl_state when calling this f= unction */ > > > +static void tsx_update_on_each_cpu(bool val) > > > +{ > > > + get_online_cpus(); > > > + on_each_cpu(tsx_update_this_cpu, (void *)val, 1); > > > + put_online_cpus(); > > > +} > >=20 > > Why take the lock? This is only called in one place. >=20 > So that TSX_CTRL MSR state stays consistent across all CPUs between > multiple on_each_cpu() calls. Otherwise overlapping conflicting TSX_CTRL = MSR > writes could end up in some CPUs with TSX enabled and others with TSX > disabled. [...] get_online_cpus() is a read lock, so it doesn't prevent concurrent updates. Ben. --=20 Ben Hutchings The obvious mathematical breakthrough [to break modern encryption] would be development of an easy way to factor large prime numbers. - Bill Gates --=-qmj1DIwVA5INE4TQwFo0 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEErCspvTSmr92z9o8157/I7JWGEQkFAl2jg6YACgkQ57/I7JWG EQkyAQ//R4vC0vfaMnOrAa5cCju5rCv6rALuarbgIASooeNTTFIyrSC4eBLCg84T D8g0JsD7wafSEs+K1aTrQq30ctTsu3dxqan0XO/SqeBkOW0853c/Un7XZvqAZBcp JWM6c7GDQD9xtFfHTREZj1sPi7V/F2Rv3BcTjSoGutdeUWwvveNkEUX3scel7eLb AUvjzP6Avsdhqc2MFhjwELm9vpI6QW4XgbLYgWwPMdA71m+xqJDBNl19K1v8PxKE kfpkReomqkyNooD2Mt1OapA5uB6+PTYvoAkGgf88MLJOE8apa4XHWPo4E+8X387g K33QnsuWO4yb+0L5LXiDonh0V4LXWWijrOFTp+iowA0xy5S0zdtwrJ7DK6uviwYX b9TtgaRakoqtcBfLTsjgxfj41pv0jsiATXMNJNKeX2FQDHlo76GGk2QAAEF1hTsw U8y6Mlbd8wAzVLmxMtNNjSEev0Ei+xm0iwhsLZAMDFqnnuO8Gm8q50Yv0QakDq2z RQhQR9YOVxep8hr2cqEpv2NAcIXxzaqyvxYv8Act2Sb1Mo3bwmO4jFgcrKG1xjGQ eR2QcgUtg3NknKPnJ0fAlSJYMdKvPSAZEtoDTzOb26xBMj5iS5JVLzRy5LIJkVZq d4H9TYVyUC5HdWZBBMmb8g0BW7zeqDh/VLQxm1qaPCKjkI4OYo4= =egyt -----END PGP SIGNATURE----- --=-qmj1DIwVA5INE4TQwFo0--