From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Bader Subject: Re: Xen HVM regression on certain Intel CPUs Date: Wed, 27 Mar 2013 18:17:14 +0100 Message-ID: <5153299A.7070108@canonical.com> References: <51530F9F.10805@canonical.com> <515315EC.4030803@canonical.com> <20130327160427.GB6688@phenom.dumpdata.com> <5153222B.3030605@canonical.com> <515323D4.2030806@zytor.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============5255424091422861218==" Return-path: In-Reply-To: <515323D4.2030806@zytor.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "H. Peter Anvin" Cc: wei.y.yang@intel.com, "xen-devel@lists.xensource.com" , haitao.shan@intel.com, xin.li@intel.com, Konrad Rzeszutek Wilk List-Id: xen-devel@lists.xenproject.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============5255424091422861218== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="------------enigA7F59ACDBEBB53BB1D3B58C0" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigA7F59ACDBEBB53BB1D3B58C0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 27.03.2013 17:52, H. Peter Anvin wrote: > On 03/27/2013 09:45 AM, Stefan Bader wrote: >> >> Rebooting with smep=3D1 as a hv argument does not fix it. But I >> would be careful since I just quickly did this without checking >> whether Xen 4.2.1 undestands the flag already. >> >> Second using x86info --all on bare metal does show bits set for=20 >> cpuid[7] and /proc/cpuinfo values are consistent across BP and >> APs. So I am a tool for using the wrong tool there. >> >> So I would say the main issue to look at is why reading cr4 as a=20 >> HVM guest produces the flags on boot. Surely the hypervisor itself=20 >> has set certain things up but likely there are some epxectations=20 >> about the initial setup on boot. >> >=20 > What does x86info and /proc/cpuinfo show in HVM? x86info cpuid[7].ebx =3D 0xbbb and /proc/cpuinfo also shows smep set. >=20 > The inbound %cr4 shouldn't matter at all, we try to not rely on it. >=20 > If the hypervisor presents SMEP to the guest then the guest is pretty > obviously going to try to use it. To me it looks like when bootstrapping the APs things are not yet ready t= o use it. If I did not miss something, the only place that the saved contents o= f cr4 are used is in startup_32 when the cpus are brought up. And then just sto= p dead. Would need to read more code but a bit weird why the BP is not affected. >=20 > -hpa >=20 > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel >=20 --------------enigA7F59ACDBEBB53BB1D3B58C0 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with undefined - http://www.enigmail.net/ iQIcBAEBCgAGBQJRUymaAAoJEOhnXe7L7s6j0/oQALfUTNSoac9bkZL0cDeCEWN/ hJXAjK+nRMtB5HiqluylD64Z8ARYdoTAC7X94ZCmCMk2ZrwFy3RsrFUGXvrCbOdZ YAsGbOnBxMomen3HD/b2ap5R2f6waVw+sUAYfLhuhByDkiUs7HrH9SFm/WeNiBMi 8edw16XmgJJfHPnn6RxxAIJEvYE2ADIFYw9CJbiGn+67ZteU/zPYlBoUawCPSTNk QmwVSbVsicbsQGVDhQ2UkNuZO6uSdq9ybj9fXsjqdbXroZYjVxIcd+6QUMcDB6OL iN9i+L815ncm9C1JRZRLmDhMD6QnAS1sIo+30T9DPwG0spAR6W8g5osVCwY4KC0U hUvlW8Syf/PGl9iOPlLf7Szlu/1k25PU2c3/xCi91QuSyXFucD72nGBp2knb2aSW zK0Ob0f3soNgSGied0fNlWihozUSJWYWbCDXo3cP9BirGsMCCBrBIyR3LJkjH0T8 B3l7DBxlXYUjP76v3tCgMrwzT2eVnGltvRNdyGOrGRP2pWtLCDLSxqkLx5EbwV1b 7vESqZvZurnS5806x7pGvVXwSp2Lx6mKggKBUev2XQ6rts7o+3ZMOYtlDjCG15N7 GYikomFdc8jNOI/2aVmxoD1mPKDRmDRoF+rQOvXNmL0wVWSXEtHba8HMvcgP6Xlq v2Gyambly0RWHoW+91Io =rSsE -----END PGP SIGNATURE----- --------------enigA7F59ACDBEBB53BB1D3B58C0-- --===============5255424091422861218== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel --===============5255424091422861218==--