From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=43090 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OOv32-00019q-TI for qemu-devel@nongnu.org; Wed, 16 Jun 2010 12:01:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OOv31-0007Ow-Bt for qemu-devel@nongnu.org; Wed, 16 Jun 2010 12:01:04 -0400 Received: from fmmailgate01.web.de ([217.72.192.221]:50343) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OOv30-0007Oj-SW for qemu-devel@nongnu.org; Wed, 16 Jun 2010 12:01:03 -0400 Message-ID: <4C18F538.1090709@web.de> Date: Wed, 16 Jun 2010 18:00:56 +0200 From: Jan Kiszka MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: [PATCH] hpet: Clean up initial hpet counter References: <4C18015C.1070306@web.de> <20100616044047.GF13238@redhat.com> <4C187725.2000902@web.de> <20100616073318.GZ21797@redhat.com> <4C188272.9010201@web.de> <20100616075259.GA21797@redhat.com> <4C1883EF.10109@web.de> <20100616090658.GC21797@redhat.com> <4C189A59.3040300@web.de> <20100616093516.GD21797@redhat.com> <20100616153607.GG523@redhat.com> In-Reply-To: <20100616153607.GG523@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigCE009C057B974B1192B1AA48" Sender: jan.kiszka@web.de List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: qemu-devel This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigCE009C057B974B1192B1AA48 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Gleb Natapov wrote: > On Wed, Jun 16, 2010 at 12:35:16PM +0300, Gleb Natapov wrote: >> On Wed, Jun 16, 2010 at 11:33:13AM +0200, Jan Kiszka wrote: >>> Gleb Natapov wrote: >>>> On Wed, Jun 16, 2010 at 09:57:35AM +0200, Jan Kiszka wrote: >>>>> Gleb Natapov wrote: >>>>>> On Wed, Jun 16, 2010 at 09:51:14AM +0200, Jan Kiszka wrote: >>>>>>> Gleb Natapov wrote: >>>>>>>> On Wed, Jun 16, 2010 at 09:03:01AM +0200, Jan Kiszka wrote: >>>>>>>>> Gleb Natapov wrote: >>>>>>>>>> On Wed, Jun 16, 2010 at 12:40:28AM +0200, Jan Kiszka wrote: >>>>>>>>>>> From: Jan Kiszka >>>>>>>>>>> >>>>>>>>>>> There is no need starting with the special value for hpet_cfg= =2Ecount. >>>>>>>>>>> Either Seabios is aware of the new firmware interface and pro= perly >>>>>>>>>>> interprets the counter or it simply ignores it anyway. >>>>>>>>>>> >>>>>>>>>> I want seabios to be able to distinguish between old qemu and = new one. >>>>>>>>> I see now. But isn't it a good chance to introduce a proper gen= eric >>>>>>>>> interface for exploring supported fw-cfg keys? >>>>>>>>> >>>>>>>> Having such interface would be nice. Pity we haven't introduced = it from >>>>>>>> the start. If we do it now seabios will have to find out somehow= that >>>>>>>> qemu support such interface. Chicken and egg ;) >>>>>>> That is easy: Add a key the describes the highest supported key v= alue >>>>>>> (looks like this is monotonously increasing). Older qemu versions= will >>>>>>> return 0. >>>>>>> >>>>>> That will not support holes in key space, and our key space is alr= eady >>>>>> sparse. >>>>> Then add a service to obtain a bitmap of supported keys. If that bi= tmap >>>>> is empty... >>>>> >>>> Bitmap will be 2k long. We can add read capability to control port. = To >>>> check if key is present you select it (write its value to control po= rt) >>>> and then read control port back. If values is non-zero the key is va= lid. >>>> But how to detect qemu that does not support that? >>> Isn't there some key that was always there and will always be? >>> >> FW_CFG_SIGNATURE >> > So any ideas? Or did I misunderstood your hint? ;) I thought you found the answer yourself: Seabios could select FW_CFG_SIGNATURE and then perform a read-back on the control register. Older QEMUs will return -1, versions that support the read-back 0. Problem solved, no? Jan --------------enigCE009C057B974B1192B1AA48 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 iEYEARECAAYFAkwY9TsACgkQitSsb3rl5xRdrgCfdRjN5mBYv+3Ryxr0pO98Un0/ UdgAoO1KdxncIW3dGKCLBSqat5LC2T3w =aQT1 -----END PGP SIGNATURE----- --------------enigCE009C057B974B1192B1AA48--