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 18:38:36 +0100 Message-ID: <51532E9C.7020806@canonical.com> References: <51530F9F.10805@canonical.com> <515315EC.4030803@canonical.com> <20130327160427.GB6688@phenom.dumpdata.com> <5153222B.3030605@canonical.com> <515323D4.2030806@zytor.com> <5153299A.7070108@canonical.com> <51532B2F.60506@zytor.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3763783497942608567==" Return-path: In-Reply-To: <51532B2F.60506@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: xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============3763783497942608567== Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="------------enig965AD8D12F50AF58A3CA68AC" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig965AD8D12F50AF58A3CA68AC Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 27.03.2013 18:23, H. Peter Anvin wrote: > On 03/27/2013 10:17 AM, Stefan Bader wrote: >>> What does x86info and /proc/cpuinfo show in HVM? >> >> x86info cpuid[7].ebx =3D 0xbbb and /proc/cpuinfo also shows smep >> set. >=20 > On all CPUs? x86info thinks its one core with ht so only one cpuid line for that. >=20 >>> The inbound %cr4 shouldn't matter at all, we try to not rely on >>> it. >>> >>> 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 to use it. If I did not miss something, the only place that >> the saved contents of cr4 are used is in startup_32 when the cpus >> are brought up. And then just stop dead. Would need to read more >> code but a bit weird why the BP is not affected. >=20 > This feels like a bug in Xen, but I don't know for sure yet. Either > which way, it is odd. That write to cr4 should be entirely legitimate.= Could likely be. Unfortunately one where a change in the kernel triggers = it. Not exactly your problem but a pita nonetheless. -Stefan >=20 > -hpa >=20 >=20 >=20 > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel >=20 --------------enig965AD8D12F50AF58A3CA68AC 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/ iQIcBAEBCgAGBQJRUy6cAAoJEOhnXe7L7s6j2E8P/1pn8rdMYGjJoGaqA50yPZWz RIKQ47p2Lu+Q/754x5qph8h5UntRwH4fTUhHSoNg5gMMjdaXrXQPQ+1d2w/3Y0S3 p9D8ws6bBSawfLRYNvpkuYmQTGa6+6P4vuBKoGXOCSdkkZslzNgeprShkuYBA3jc Vm7sFr0oVwWhMfqOEnWjfgRxTil+izHg9CB+bib1PPMQcd3jas17+k2ZsiNTCIMQ ZoAcN3rbjyHc9+69nxL4TdHvRruD2FIKNmMS+mJOzi1/nMYRbfYvPbcvbr3OOfr0 tzGGazKA9aiGKTavXt/u9TsJgsXKaKTW4FTGq5Z/RSF2rmjc3QyRmKMWwxL+M1oN pFukGSDcdS4w4gCxxS+A1LgW+ZGzwOXTDFU0CGYY980DdzwSijigDer5Gob1YKsk BVZVXNclB7kQt0G4pbwz2PjlZ/Lldk0WFP0oFiDwNJFW+9+d6yaosv0vcakjK3a7 wfjGVRlBEuO1QAY9q0Jjj3r3gVOtitv6bO2dyNSheC6/zpHGG49u1Bi1sue0Nc6T zMwonGTD6py1vOGJEkBHwDxg8SOhGRAFtQYbMqVeyBCTrzLIg5127e1eiippnqku VWrrITBIPxdZxiy3Rj9j1nQjdBSakMmHxnZ7h7itLSUA5m8AbqTt0aLyzrt60mFP hIR4jV8z+GEhqIYJ/Ura =r0f9 -----END PGP SIGNATURE----- --------------enig965AD8D12F50AF58A3CA68AC-- --===============3763783497942608567== 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 --===============3763783497942608567==--