From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:44882) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QmUxD-0006g0-6o for qemu-devel@nongnu.org; Thu, 28 Jul 2011 14:05:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QmUxB-0003GI-II for qemu-devel@nongnu.org; Thu, 28 Jul 2011 14:05:03 -0400 Received: from fmmailgate02.web.de ([217.72.192.227]:47217) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QmUxB-0003Fh-67 for qemu-devel@nongnu.org; Thu, 28 Jul 2011 14:05:01 -0400 Message-ID: <4E31A4CA.80402@web.de> Date: Thu, 28 Jul 2011 20:04:58 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <20110727154229.656532d4@doriath> <4E310E6A.6000004@redhat.com> <20110728103143.548d7bb1@doriath> <4E3165FD.7040805@redhat.com> <4E316FE7.6030005@web.de> <20110728121811.11dc8434@doriath> <4E317E49.5090708@web.de> <20110728143923.3183d349@doriath> <20110728144831.766fa270@doriath> <4E31A1DF.2050702@web.de> <20110728150007.6d8bc9db@doriath> In-Reply-To: <20110728150007.6d8bc9db@doriath> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig376759AA7CA894E65E7EF750" Sender: jan.kiszka@web.de Subject: Re: [Qemu-devel] [RFC] Introduce vm_stop_permanent() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino Cc: Blue Swirl , Avi Kivity , qemu-devel This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig376759AA7CA894E65E7EF750 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2011-07-28 20:00, Luiz Capitulino wrote: > On Thu, 28 Jul 2011 19:52:31 +0200 > Jan Kiszka wrote: >=20 >> On 2011-07-28 19:48, Luiz Capitulino wrote: >>> On Thu, 28 Jul 2011 14:39:23 -0300 >>> Luiz Capitulino wrote: >>> >>>> On Thu, 28 Jul 2011 17:20:41 +0200 >>>> Jan Kiszka wrote: >>>> >>>>> On 2011-07-28 17:18, Luiz Capitulino wrote: >>>>>> On Thu, 28 Jul 2011 16:19:19 +0200 >>>>>> Jan Kiszka wrote: >>>>>> >>>>>>> On 2011-07-28 15:37, Avi Kivity wrote: >>>>>>>> On 07/28/2011 04:31 PM, Luiz Capitulino wrote: >>>>>>>>> On Thu, 28 Jul 2011 10:23:22 +0300 >>>>>>>>> Avi Kivity wrote: >>>>>>>>> >>>>>>>>>> On 07/28/2011 12:44 AM, Blue Swirl wrote: >>>>>>>>>> > On Wed, Jul 27, 2011 at 9:42 PM, Luiz >>>>>>>>> Capitulino wrote: >>>>>>>>>> > > This function should be used when the VM is not suppos= ed to >>>>>>>>> resume >>>>>>>>>> > > execution (eg. by issuing 'cont' monitor command). >>>>>>>>>> > > >>>>>>>>>> > > Today, we allow the user to resume execution even when= : >>>>>>>>>> > > >>>>>>>>>> > > o the guest shuts down and -no-shutdown is used >>>>>>>>>> > > o there's a kvm internal error >>>>>>>>>> > > o loading the VM state with -loadvm or "loadvm" in t= he >>>>>>>>> monitor fails >>>>>>>>>> > > >>>>>>>>>> > > I think only badness can happen from the cases above. >>>>>>>>>> > >>>>>>>>>> > I'd suppose a system_reset should bring the system back to= >>>>>>>>> sanity and >>>>>>>>>> > then clear vm_permanent_stopped (where's -ly?) >>>>>>>>> >>>>>>>>> What's -ly? >>>>>>>>> >>>>>>>> >>>>>>>> permanent-ly. >>>>>>>> >>>>>>>>>> > except maybe for KVM >>>>>>>>>> > internal error if that can't be recovered. Then it would n= ot very >>>>>>>>>> > permanent anymore, so the name would need adjusting. >>>>>>>>>> >>>>>>>>>> Currently, all kvm internal errors are recoverable by reset (= and >>>>>>>>>> possibly by fiddling with memory/registers). >>>>>>>>> >>>>>>>>> Ok, but a poweroff in the guest isn't recoverable with system_r= eset >>>>>>>>> right? Or does it depend on the guest? >>>>>>>> >>>>>>>> Right, it's not recoverable if you shut the power down where the= tractor >>>>>>>> beam is coupled to the main reactor. >>>>>>> >>>>>>> system_reset will bring all emulated devices back into their powe= r-on >>>>>>> state - unless we have remaining bugs to fix. Actually, one may c= onsider >>>>>>> issuing this reset automatically on vm_start after "permant" vm_s= top. >>>> >>>> The only permanent vm_stop we'd have is poweroff when -no-shutdown i= s used. >>>> >>>> Are you saying that system_reset should be able to recover from that= too? >>> >>> It already does, so we don't have permanent stops. >> >> Exactly. We just have stops over inconsistent states that require a >> reset to continue with anything useful. >=20 > Yes. If I got you right, you suggest that we do the reset automatically= =2E >=20 > I think it's better to let the user do it, because s/he might want to > do something else before resetting. For example, for the kvm error the > user might want to save the vm state. Associating the reset with a cont means requesting an explicit action from the user. I'm not suggesting to do the reset when the stop state is entered. >=20 > For the poweroff case with -no-shutdown it's probably fine, but I don't= > want to hard code special cases. It's better and easier to treat them a= ll > as "require system_reset to recover". In any case, we need to tag the current state as stopped-and-invalid or so vs. a normal stop. That remains a valuable first step. How to deal with that information is the second one. Jan --------------enig376759AA7CA894E65E7EF750 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk4xpMoACgkQitSsb3rl5xRC2gCgygvJ+N3vLAsJHex5OuCKcjdK nZcAnR96Kjkxa3kPwr8qB4pjzGpp8Wl4 =+hhT -----END PGP SIGNATURE----- --------------enig376759AA7CA894E65E7EF750--