From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH] KVM: VMX: Update instruction length on intercepted BP Date: Sun, 14 Feb 2010 11:47:58 +0100 Message-ID: <4B77D4DE.3030602@web.de> References: <4B767160.4070609@web.de> <20100214075303.GF2511@redhat.com> <4B77CFD7.9080504@web.de> <20100214103445.GH2511@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigEE91897362AE8426DB914F9F" Cc: Avi Kivity , Marcelo Tosatti , kvm To: Gleb Natapov Return-path: Received: from fmmailgate03.web.de ([217.72.192.234]:53628 "EHLO fmmailgate03.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753410Ab0BNKsJ (ORCPT ); Sun, 14 Feb 2010 05:48:09 -0500 In-Reply-To: <20100214103445.GH2511@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigEE91897362AE8426DB914F9F Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Gleb Natapov wrote: > On Sun, Feb 14, 2010 at 11:26:31AM +0100, Jan Kiszka wrote: >> Gleb Natapov wrote: >>> On Sat, Feb 13, 2010 at 10:31:12AM +0100, Jan Kiszka wrote: >>>> From: Jan Kiszka >>>> >>>> We intercept #BP while in guest debugging mode. As VM exists due to >>>> intercepted exceptions do not necessarily come with valid >>>> idt_vectoring, we have to update event_exit_inst_len explicitly in s= uch >>>> cases. At least in the absence of migration, this ensures that >>>> re-injections of #BP will find and use the correct instruction lengt= h. >>>> >>> event_exit_inst_len is only used for event reinjection. Since event >>> intercepted here will not be reinjected why updating event_exit_inst_= len >>> is needed here? >> In guest debugging mode a #BP exception is always reported to user spa= ce >> to find out what caused it. If it was the guest itself, the exception = is >> reinjected, on older kernels via KVM_SET_GUEST_DEBUG and since 2.6.33 >> via KVM_SET_VCPU_EVENTS (the latter requires some qemu patch that I wi= ll >> post later). >> >> As we currently do not update event_exit_inst_len on #BP exits, >> reinjecting fails unless event_exit_inst_len happens to be 1 from some= >> other exit. >> > Hmm, how does it work on SVM then where we do not have > event_exit_inst_len so execution will resume on the same rip that cause= d > #BP after event reinjection? >=20 Maybe not at all. I don't think I've tested this scenario on amd so far. Guess it needs some special handling in svm to move rip after the int3 when requesting to inject #BP. Jan --------------enigEE91897362AE8426DB914F9F Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAkt31OMACgkQitSsb3rl5xSbrACg20XyOfjE19BqaggOa3n++N/v XXIAoOpjQp5sjtgBmO/8YCo/MmMZAmoV =QTx/ -----END PGP SIGNATURE----- --------------enigEE91897362AE8426DB914F9F--