From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Blake Subject: Re: [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request Date: Fri, 28 Apr 2017 13:05:43 -0500 Message-ID: <2b7417be-559c-b1e5-eaf4-e195d611b4d6@redhat.com> References: <20170428021317.24711-1-eblake@redhat.com> <20170428021317.24711-3-eblake@redhat.com> <20170428080821.GB2085@work-vm> <3a8d9f68-f30c-1191-ca80-a93f0050f011@redhat.com> <20170428152729.GI2085@work-vm> <550a4e37-c4b3-181d-876c-64d73e96e78c@redhat.com> <20170428160901.GK2085@work-vm> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============2703257031890794168==" Return-path: Received: from mail6.bemta6.messagelabs.com ([193.109.254.103]) by lists.xenproject.org with esmtp (Exim 4.84_2) (envelope-from ) id 1d4AHD-0000rs-TQ for xen-devel@lists.xenproject.org; Fri, 28 Apr 2017 18:05:55 +0000 In-Reply-To: <20170428160901.GK2085@work-vm> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xen.org Sender: "Xen-devel" To: "Dr. David Alan Gilbert" Cc: Stefano Stabellini , berrange@redhat.com, Eduardo Habkost , "Michael S. Tsirkin" , armbru@redhat.com, Juan Quintela , qemu-devel@nongnu.org, alistair.francis@xilinx.com, zhanghailiang , "open list:X86" , Anthony Perard , Paolo Bonzini , Richard Henderson List-Id: xen-devel@lists.xenproject.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --===============2703257031890794168== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="CvgU3k0SnljQChjEk84X6rK4WdmUC8FxU" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --CvgU3k0SnljQChjEk84X6rK4WdmUC8FxU Content-Type: multipart/mixed; boundary="mGEe8aVOcAO5mKqhVUO4kIkHSEiRFCuN3"; protected-headers="v1" From: Eric Blake To: "Dr. David Alan Gilbert" Cc: qemu-devel@nongnu.org, armbru@redhat.com, berrange@redhat.com, alistair.francis@xilinx.com, Stefano Stabellini , Anthony Perard , "Michael S. Tsirkin" , Paolo Bonzini , Richard Henderson , Eduardo Habkost , zhanghailiang , Juan Quintela , "open list:X86" Message-ID: <2b7417be-559c-b1e5-eaf4-e195d611b4d6@redhat.com> Subject: Re: [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request References: <20170428021317.24711-1-eblake@redhat.com> <20170428021317.24711-3-eblake@redhat.com> <20170428080821.GB2085@work-vm> <3a8d9f68-f30c-1191-ca80-a93f0050f011@redhat.com> <20170428152729.GI2085@work-vm> <550a4e37-c4b3-181d-876c-64d73e96e78c@redhat.com> <20170428160901.GK2085@work-vm> In-Reply-To: <20170428160901.GK2085@work-vm> --mGEe8aVOcAO5mKqhVUO4kIkHSEiRFCuN3 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 04/28/2017 11:09 AM, Dr. David Alan Gilbert wrote: >>> At a higher level, using your tags, I'm not sure where a reset trigge= red >>> by a fault detected by the hypervisor lives - e.g. an x86 triple faul= t >>> where the guest screws up so badly that it just gets reset. Is >>> that a guest-reset or a guest-panic or what - neither case >>> was actually asked for by the guest itself. >> >> Wouldn't that be host-error (qemu detected an error that prevents >> further execution of the guest without a reset - and a triple fault >> seems to fall into the category of the guest getting itself wedged >> rather than actually trying to reset)? Except patch 3 only used >> SHUTDOWN_TYPE_HOST_ERROR in the xen portion of the patch. >> >> So if any x86 expert has an opinion on where triple-fault handling is >> emulated, and what category should be used there, I'm welcome to >> tweaking this series. >=20 > It's pretty much on the border anyway, I don't think it matters too > much; it sounds perfectly reasonable. Actually, reading https://blogs.msdn.microsoft.com/larryosterman/2005/02/08/faster-syscall-= trap-redux/ makes it sound like the triple-fault =3D reset is exploited by existing O= S (dating back to days of targetting 286 machines), so it is bare-metal behavior that we have to faithfully emulate as a guest-triggered reset, and not something where the guest has wedged itself to the point where qemu can no longer execute the guest. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org --mGEe8aVOcAO5mKqhVUO4kIkHSEiRFCuN3-- --CvgU3k0SnljQChjEk84X6rK4WdmUC8FxU 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 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJZA4R3AAoJEKeha0olJ0Nqm/sH/1XrnQIue9wTuZstiD/cf0nX ufrJ6tySWwtNxx4r4nnjtHp0DXLkqyiNtsesnZtgJXkY6dYO/Awilz879zK+mdOI 85u4PNSgZ2dm0H1MGTurQSxkh56u2nWMrt1iX+pjtHLBItZ6Pn4WLTVsSxMeiXC6 6MLJgxfTrptujUzOy9IWvYluHy4HhHRgqD1Qny4jFQ6lnfqRjtFBhdEy3Y5/hyEt p+lptuS+V5AnsXHvL+zbi5VUz4oyr5guooCM8IpE26X4vSg611NSPpIWy2wsssm8 NaE+yK5BK9PeY+JRodLu0zgI4/foLAZyXyzyThunv+ImpmRcuuXkqetohQ8c7MY= =H5IP -----END PGP SIGNATURE----- --CvgU3k0SnljQChjEk84X6rK4WdmUC8FxU-- --===============2703257031890794168== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVuLm9yZwpodHRwczovL2xpc3RzLnhlbi5v cmcveGVuLWRldmVsCg== --===============2703257031890794168==--