From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=56604 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q7mVl-0004WY-AO for qemu-devel@nongnu.org; Thu, 07 Apr 2011 06:32:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Q7mHn-0008H0-Lm for qemu-devel@nongnu.org; Thu, 07 Apr 2011 06:18:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49779) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Q7mHn-0008Gj-87 for qemu-devel@nongnu.org; Thu, 07 Apr 2011 06:17:59 -0400 Message-ID: <4D9D8FE0.4070107@redhat.com> Date: Thu, 07 Apr 2011 12:20:16 +0200 From: Kevin Wolf MIME-Version: 1.0 References: <4D9D7CE8.7070001@redhat.com> <20110407091139.GC11546@amit-x200.redhat.com> In-Reply-To: <20110407091139.GC11546@amit-x200.redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH v2 1/2] cdrom: Allow the TEST_UNIT_READY command after a cdrom change List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Amit Shah Cc: Gleb Natapov , Juan Quintela , Stefan Hajnoczi , Markus Armbruster , qemu list Am 07.04.2011 11:11, schrieb Amit Shah: > On (Thu) 07 Apr 2011 [10:59:20], Kevin Wolf wrote: >> Am 07.04.2011 07:05, schrieb Amit Shah: >>> We restrict the commands that a guest can send us after a cdrom change >>> event. The current list includes REQUEST_SENSE and INQUIRY commands. >>> Guests can also issue TEST_UNIT_READY to inquire for the status, so >>> allow this command as well. >>> >>> Signed-off-by: Amit Shah >> >> Hm... MMC-5, section 4.1.6.1 seems to conflict with this: >> >> "If a Host issues a command other than GET CONFIGURATION, GET EVENT >> STATUS NOTIFICATION, INQUIRY or REQUEST SENSE while a unit attention >> condition exists for that Host, the Drive shall not perform the command >> and shall report CHECK CONDITION status unless a higher priority status >> as defined by the Drive is also pending." >> >> So while you're right that our list is incomplete, TEST UNIT READY >> doesn't seem to be among the missing commands. > > Hm - older Linux guests (pre 2.6.38) and Windows guests, as Gleb's > commit mentioned, rely on this command to get CD change notifications: > > /* identical to scsi_test_unit_ready except that it doesn't > * eat the NOT_READY returns for removable media */ > int sr_test_unit_ready(struct scsi_device *sdev, struct scsi_sense_hdr *sshdr) > { > int retries = MAX_RETRIES; > int the_result; > u8 cmd[] = {TEST_UNIT_READY, 0, 0, 0, 0, 0 }; > > /* issue TEST_UNIT_READY until the initial startup UNIT_ATTENTION > * conditions are gone, or a timeout happens > */ > do { > the_result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, > 0, sshdr, SR_TIMEOUT, > retries--, NULL); > if (scsi_sense_valid(sshdr) && > sshdr->sense_key == UNIT_ATTENTION) > sdev->changed = 1; > > } while (retries > 0 && > (!scsi_status_is_good(the_result) || > (scsi_sense_valid(sshdr) && > sshdr->sense_key == UNIT_ATTENTION))); > return the_result; > } I think the scsi_execute_req() call might issue a REQUEST SENSE internally and therefore clear the unit attention condition. Tried to check that in the source, but I'm hopelessly lost in the kernel... Kevin