I'm a new subscriber to seabios.org so feel free to straighten me out if needed.
I've been debugging an problem we've been seeing with not being able to boot (Ubuntu specifically) off of a variety of "newer" USB thumb drives. I've been specifically looking at an older/newer pair of Sandisk Cruzer 4GB drives. I've been adding dprintf's to narrow down the problem to the blockcmd.c file. The function scsi_init_drive() queries the USB device to determine stuff like vendor/device/size/etc. Near the end of the function is a call to cdb_mode_sense_geom(&dop, &geomdata) to retrieve the info related to cyl/head type stuff. On the older/working thumbdrive it returns zeroes for all of the values that get used by the code. The newer/failing drive generates a "stall" on the USB bus, which it never recovers from. The cdb_mode_sense_geom() function is sending a SCSI CDB Mode Sense (CMD=0x5A) to the device.
As a hack of a test, I removed the call to cdb_mode_sense_geom() and filled the buffer it should have returned with zeroes and the failing thumbdrive now boots.
I have some searching I need to do to find out... 1) Is there a SCSI command to determine what protocols are supported? 2) Is there another SCSI command that might return similar required data?
Has anyone out there experienced similar booting difficulties? Or does anyone have any recommendations on what approach I should take?
thanks, Dave
Maybe run: lsusb -v and compare the output for the difference SanDisk Cruzer USB devices if they're identical or different.
On Thu, Mar 1, 2012 at 12:38 AM, Dave Frodin dave@camp.se-eng.com wrote:
I'm a new subscriber to seabios.org so feel free to straighten me out if needed.
I've been debugging an problem we've been seeing with not being able to boot (Ubuntu specifically) off of a variety of "newer" USB thumb drives. I've been specifically looking at an older/newer pair of Sandisk Cruzer 4GB drives. I've been adding dprintf's to narrow down the problem to the blockcmd.c file. The function scsi_init_drive() queries the USB device to determine stuff like vendor/device/size/etc. Near the end of the function is a call to cdb_mode_sense_geom(&dop, &geomdata) to retrieve the info related to cyl/head type stuff. On the older/working thumbdrive it returns zeroes for all of the values that get used by the code. The newer/failing drive generates a "stall" on the USB bus, which it never recovers from. The cdb_mode_sense_geom() function is sending a SCSI CDB Mode Sense (CMD=0x5A) to the device.
As a hack of a test, I removed the call to cdb_mode_sense_geom() and filled the buffer it should have returned with zeroes and the failing thumbdrive now boots.
I have some searching I need to do to find out...
- Is there a SCSI command to determine what protocols are supported?
- Is there another SCSI command that might return similar required data?
Has anyone out there experienced similar booting difficulties? Or does anyone have any recommendations on what approach I should take?
thanks, Dave
SeaBIOS mailing list SeaBIOS@seabios.org http://www.seabios.org/mailman/listinfo/seabios
I have some addition results and questions.
I changed the "page mode" value that is in the struct sent in the MODE SENSE command from the existing value of 04h (rigid disk) to 05h (flexible disk). This change increased the number of passing USB thumbdrives from 6 to 10. I'm testing with a total of 12 different vendor/size drives.
The two failing drives still send a USB stall but the failure mode is different. With the page mode type set to 4 the failure sequence was ... 1) send MODE SENSE command to drive => device accepts data and ACKs 2) device stalls the USB bus With the page mode set to 5 the failure sequence is ... 1) send MODE SENSE command to drive => device accepts data and ACKs 2) device sends response => host accepts data and ACKs 3) device stalls the USB bus Also, the device only sends 6 bytes instead of the requested 27 bytes.
I'm planning on seeing if there isn't something missing prior to the mode sense command tomorrow.
On a related topic, I have a copy of the "Indispensable PC Hardware" book that lists the return values for the mode page 4 request. It list the cyc/head data as follows... offset value ================== 2 cyl(msb) 3 cyl 4 cyl(lsb) 5 heads
the struct in the blockcmd.h file shows... struct cdbres_mode_sense_geom { u8 unused_00[3]; u8 read_only; u32 unused_04; u8 page; u8 length; u8 cyl[3]; u8 heads; u8 precomp[3]; u8 reduced[3]; u16 step_rate; u8 landing[3]; u16 rpm; } PACKED; which would put cyl[3] at offset 10 thru 12 and heads at offset 13. Am I missing something here?
USB thumbdrives that don't stall on the mode sense return values like cyl = 10h 3Fh 02h heads = 00h ???
The values for that drive have 00h at offsets 2 thru 5.
I'm looking forward to any insight into this from anyone knowledgeable on the subject.
Dave
----- Original Message -----
From: "Dave Frodin" dave@camp.se-eng.com To: seabios@seabios.org Sent: Wednesday, February 29, 2012 4:38:21 PM Subject: [SeaBIOS] Booting from USB thumbdrives, older drives boot, newer drives don't.
I'm a new subscriber to seabios.org so feel free to straighten me out if needed.
I've been debugging an problem we've been seeing with not being able to boot (Ubuntu specifically) off of a variety of "newer" USB thumb drives. I've been specifically looking at an older/newer pair of Sandisk Cruzer 4GB drives. I've been adding dprintf's to narrow down the problem to the blockcmd.c file. The function scsi_init_drive() queries the USB device to determine stuff like vendor/device/size/etc. Near the end of the function is a call to cdb_mode_sense_geom(&dop, &geomdata) to retrieve the info related to cyl/head type stuff. On the older/working thumbdrive it returns zeroes for all of the values that get used by the code. The newer/failing drive generates a "stall" on the USB bus, which it never recovers from. The cdb_mode_sense_geom() function is sending a SCSI CDB Mode Sense (CMD=0x5A) to the device.
As a hack of a test, I removed the call to cdb_mode_sense_geom() and filled the buffer it should have returned with zeroes and the failing thumbdrive now boots.
I have some searching I need to do to find out...
- Is there a SCSI command to determine what protocols are supported?
- Is there another SCSI command that might return similar required
data?
Has anyone out there experienced similar booting difficulties? Or does anyone have any recommendations on what approach I should take?
thanks, Dave
SeaBIOS mailing list SeaBIOS@seabios.org http://www.seabios.org/mailman/listinfo/seabios
Il 02/03/2012 01:34, Dave Frodin ha scritto:
On a related topic, I have a copy of the "Indispensable PC Hardware" book that lists the return values for the mode page 4 request. It list the cyc/head data as follows... offset value ================== 2 cyl(msb) 3 cyl 4 cyl(lsb) 5 heads
the struct in the blockcmd.h file shows... struct cdbres_mode_sense_geom { u8 unused_00[3]; u8 read_only; u32 unused_04; u8 page; u8 length; u8 cyl[3]; u8 heads; u8 precomp[3]; u8 reduced[3]; u16 step_rate; u8 landing[3]; u16 rpm; } PACKED; which would put cyl[3] at offset 10 thru 12 and heads at offset 13. Am I missing something here?
The first eight bytes are not part of the page, they are common to all MODE SENSE responses.
Perhaps we could restrict the MODE SENSE to disks of 504MiB and less. I still have a couple of 256 MB pen drives around, I can test them.
Can you try "sg_modes -HHp 4 /dev/sda" (from Linux) on both those that fail and those that work?
Paolo
Paolo, Thanks for the reply. I ran the sg_modes for pages 4 and 5 on 4 USB thumbdrives. sandisk_old is a 4GB Sandisk Cruzer (yes, the old is ver=8.02) sandisk_new is a 4GB Sandisk Cruzer transcend is a 2GB drive verbatim is a 2GB drive
If I use the unmodified "master" SeaBIOS ... sandisk_old boots sandisk_new stalls at mode sense transcend stalls at mode sense verbatim boots
If I change the mode page from 4 to 5 ... sandisk_old boots sandisk_new boots transcend stalls at mode sense verbatim boots
The mode page change from 4 to 5 allowed four of my none booting drives to boot. Hopefully these logs will be helpful.
Thanks again, dave
starting sandisk_old tests sudo sg_modes -HHp 4 /dev/sdb SanDisk Cruzer 8.02 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 46 00 00 00 00 00 00 Mode data length=72, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0 >> page_code=0x0, page_control=0 00 00 00 Unexpectedly received extra mode page responses, ignore
sudo sg_modes -HHp 5 /dev/sdb SanDisk Cruzer 8.02 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 26 00 00 00 00 00 00 Mode data length=40, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0 >> page_code=0x5, page_control=0 00 05 1e 80 00 04 20 02 00 ef c0 00 00 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
starting sandisk_new tests sudo sg_modes -HHp 4 /dev/sdb SanDisk Cruzer 1.26 peripheral_type: disk [0x0] invalid field in cdb (perhaps page 0x4 not supported)
sudo sg_modes -HHp 5 /dev/sdb SanDisk Cruzer 1.26 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 26 00 00 00 00 00 00 Mode data length=40, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0 >> page_code=0x5, page_control=0 00 05 1e 00 00 10 3f 02 00 1e 4f 00 00 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
starting transcend sudo sg_modes -HHp 4 /dev/sdb JetFlash Transcend 2GB 8.07 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 06 00 00 00 00 00 00 Mode data length=8, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
sudo sg_modes -HHp 5 /dev/sdb JetFlash Transcend 2GB 8.07 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 06 00 00 00 00 00 00 Mode data length=8, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
starting verbatim sudo sg_modes -HHp 4 /dev/sdb Verbatim STORE N GO 5.00 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 06 00 00 00 00 00 00 Mode data length=8, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
sudo sg_modes -HHp 5 /dev/sdb Verbatim STORE N GO 5.00 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 26 00 00 00 00 00 00 Mode data length=40, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0 >> page_code=0x5, page_control=0 00 05 1e f0 00 ff 20 02 00 01 df 00 00 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
----- Original Message -----
From: "Paolo Bonzini" pbonzini@redhat.com To: seabios@seabios.org, dave@camp.se-eng.com Sent: Friday, March 2, 2012 7:20:28 AM Subject: Re: Booting from USB thumbdrives, older drives boot, newer drives don't.
Il 02/03/2012 01:34, Dave Frodin ha scritto:
On a related topic, I have a copy of the "Indispensable PC Hardware" book that lists the return values for the mode page 4 request. It list the cyc/head data as follows... offset value ================== 2 cyl(msb) 3 cyl 4 cyl(lsb) 5 heads
the struct in the blockcmd.h file shows... struct cdbres_mode_sense_geom { u8 unused_00[3]; u8 read_only; u32 unused_04; u8 page; u8 length; u8 cyl[3]; u8 heads; u8 precomp[3]; u8 reduced[3]; u16 step_rate; u8 landing[3]; u16 rpm; } PACKED; which would put cyl[3] at offset 10 thru 12 and heads at offset 13. Am I missing something here?
The first eight bytes are not part of the page, they are common to all MODE SENSE responses.
Perhaps we could restrict the MODE SENSE to disks of 504MiB and less. I still have a couple of 256 MB pen drives around, I can test them.
Can you try "sg_modes -HHp 4 /dev/sda" (from Linux) on both those that fail and those that work?
Paolo
Here are my latest results. The sg_modes command has a "-a" option to dump out all of the supported page codes - it reports that none of the thumbdrives (tested 9) support page code = 4 - it reports that most of the thumbdrives (tested 9) support page code = 5 - it commented that page code 5 is obsolete
the page_code=4 and 5 cyc/head info must be garbage these are the types of values I get back. I haven't found a spec yet for the page_code 5 geometry struct so it could be bogus because of that.
cyc[0]/cyc[1]/cyc[2] head ------------------------------- page_code 4 page_code 5 ================================================ old_sandisk 00/00/00 0 80/00/04 20 new_sandisk stall 00/00/10 3F verbatim 66/b5/02 f f0/00/ff 20 wintec 00/00/80 0 13/88/10 3F
I think the booting drives boot because ... A) using page_code=5 got rid of the stall (even though the data is bogus) B) the MBR is at sector 0, and 0 is 0 no matter what the geometry C) perhaps there is code later in seabios that understands it's booting from a USB drive and knows better than us what to do and uses something like linear sectors.
Marc suggested that I leave the page_code set to 4 in order to preserve functionality for drives that actually report valid CHS geometry, and to add code that would clear the stall from the USB controller and thumbdrive.
Questions: 1) Any recommendations on my direction? 2) Is there any way to differentiate between a USB thumbdrive and a USB-to-SATA adapter?
dave
----- Original Message -----
From: "Dave Frodin" dave@camp.se-eng.com To: seabios@seabios.org Sent: Friday, March 2, 2012 8:53:54 AM Subject: Re: [SeaBIOS] Booting from USB thumbdrives, older drives boot, newer drives don't.
Paolo, Thanks for the reply. I ran the sg_modes for pages 4 and 5 on 4 USB thumbdrives. sandisk_old is a 4GB Sandisk Cruzer (yes, the old is ver=8.02) sandisk_new is a 4GB Sandisk Cruzer transcend is a 2GB drive verbatim is a 2GB drive
If I use the unmodified "master" SeaBIOS ... sandisk_old boots sandisk_new stalls at mode sense transcend stalls at mode sense verbatim boots
If I change the mode page from 4 to 5 ... sandisk_old boots sandisk_new boots transcend stalls at mode sense verbatim boots
The mode page change from 4 to 5 allowed four of my none booting drives to boot. Hopefully these logs will be helpful.
Thanks again, dave
starting sandisk_old tests sudo sg_modes -HHp 4 /dev/sdb SanDisk Cruzer 8.02 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 46 00 00 00 00 00 00 Mode data length=72, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
page_code=0x0, page_control=0
00 00 00 Unexpectedly received extra mode page responses, ignore
sudo sg_modes -HHp 5 /dev/sdb SanDisk Cruzer 8.02 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 26 00 00 00 00 00 00 Mode data length=40, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
page_code=0x5, page_control=0
00 05 1e 80 00 04 20 02 00 ef c0 00 00 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
starting sandisk_new tests sudo sg_modes -HHp 4 /dev/sdb SanDisk Cruzer 1.26 peripheral_type: disk [0x0] invalid field in cdb (perhaps page 0x4 not supported)
sudo sg_modes -HHp 5 /dev/sdb SanDisk Cruzer 1.26 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 26 00 00 00 00 00 00 Mode data length=40, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
page_code=0x5, page_control=0
00 05 1e 00 00 10 3f 02 00 1e 4f 00 00 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
starting transcend sudo sg_modes -HHp 4 /dev/sdb JetFlash Transcend 2GB 8.07 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 06 00 00 00 00 00 00 Mode data length=8, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
sudo sg_modes -HHp 5 /dev/sdb JetFlash Transcend 2GB 8.07 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 06 00 00 00 00 00 00 Mode data length=8, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
starting verbatim sudo sg_modes -HHp 4 /dev/sdb Verbatim STORE N GO 5.00 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 06 00 00 00 00 00 00 Mode data length=8, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
sudo sg_modes -HHp 5 /dev/sdb Verbatim STORE N GO 5.00 peripheral_type: disk [0x0] Mode parameter header from MODE SENSE(10): 00 00 26 00 00 00 00 00 00 Mode data length=40, medium type=0x00, WP=0, DpoFua=0, longlba=0 Block descriptor length=0
page_code=0x5, page_control=0
00 05 1e f0 00 ff 20 02 00 01 df 00 00 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
----- Original Message -----
From: "Paolo Bonzini" pbonzini@redhat.com To: seabios@seabios.org, dave@camp.se-eng.com Sent: Friday, March 2, 2012 7:20:28 AM Subject: Re: Booting from USB thumbdrives, older drives boot, newer drives don't.
Il 02/03/2012 01:34, Dave Frodin ha scritto:
On a related topic, I have a copy of the "Indispensable PC Hardware" book that lists the return values for the mode page 4 request. It list the cyc/head data as follows... offset value ================== 2 cyl(msb) 3 cyl 4 cyl(lsb) 5 heads
the struct in the blockcmd.h file shows... struct cdbres_mode_sense_geom { u8 unused_00[3]; u8 read_only; u32 unused_04; u8 page; u8 length; u8 cyl[3]; u8 heads; u8 precomp[3]; u8 reduced[3]; u16 step_rate; u8 landing[3]; u16 rpm; } PACKED; which would put cyl[3] at offset 10 thru 12 and heads at offset 13. Am I missing something here?
The first eight bytes are not part of the page, they are common to all MODE SENSE responses.
Perhaps we could restrict the MODE SENSE to disks of 504MiB and less. I still have a couple of 256 MB pen drives around, I can test them.
Can you try "sg_modes -HHp 4 /dev/sda" (from Linux) on both those that fail and those that work?
Paolo
SeaBIOS mailing list SeaBIOS@seabios.org http://www.seabios.org/mailman/listinfo/seabios
On Fri, Mar 02, 2012 at 03:10:33PM -0700, Dave Frodin wrote:
Here are my latest results. The sg_modes command has a "-a" option to dump out all of the supported page codes
- it reports that none of the thumbdrives (tested 9) support page code = 4
- it reports that most of the thumbdrives (tested 9) support page code = 5
- it commented that page code 5 is obsolete
Thanks Dave. I appreciate your detailed analysis.
The call to cdb_mode_sense_geom() was only recently added. I'm inclined to just remove the call. Paolo, is there a use case where having the "physical" chs info is important? SeaBIOS should generate good "virtual" chs info regardless, and the underlying "physical" info is only exported in a couple of places.
Marc suggested that I leave the page_code set to 4 in order to preserve functionality for drives that actually report valid CHS geometry, and to add code that would clear the stall from the USB controller and thumbdrive.
The SeaBIOS code really should know how to clear a stall. However, it's a bit of a pain to do that in the general case. (In the general case, we'd need to support clearing the stall from 16bit mode, which would require the ability to send control messages to the drive in 16bit mode.)
- Is there any way to differentiate between a USB thumbdrive and a USB-to-SATA adapter?
I don't know of a way to detect it, but I haven't looked closely.
-Kevin
Kevin/Paolo, Our concern was that actual rotating media (e.g. USB-to-SATA adapter) may have problems without the cdb_mode_sense_geom(). I hope to have my hands on one tomorrow to do some testing.
Dave
----- Original Message -----
From: "Kevin O'Connor" kevin@koconnor.net To: "Dave Frodin" dave@camp.se-eng.com, "Paolo Bonzini" pbonzini@redhat.com Cc: seabios@seabios.org Sent: Sunday, March 4, 2012 11:49:30 AM Subject: Re: [SeaBIOS] Booting from USB thumbdrives, older drives boot, newer drives don't.
On Fri, Mar 02, 2012 at 03:10:33PM -0700, Dave Frodin wrote:
Here are my latest results. The sg_modes command has a "-a" option to dump out all of the supported page codes
- it reports that none of the thumbdrives (tested 9) support
page code = 4
- it reports that most of the thumbdrives (tested 9) support
page code = 5
- it commented that page code 5 is obsolete
Thanks Dave. I appreciate your detailed analysis.
The call to cdb_mode_sense_geom() was only recently added. I'm inclined to just remove the call. Paolo, is there a use case where having the "physical" chs info is important? SeaBIOS should generate good "virtual" chs info regardless, and the underlying "physical" info is only exported in a couple of places.
Marc suggested that I leave the page_code set to 4 in order to preserve functionality for drives that actually report valid CHS geometry, and to add code that would clear the stall from the USB controller and thumbdrive.
The SeaBIOS code really should know how to clear a stall. However, it's a bit of a pain to do that in the general case. (In the general case, we'd need to support clearing the stall from 16bit mode, which would require the ability to send control messages to the drive in 16bit mode.)
- Is there any way to differentiate between a USB thumbdrive and a USB-to-SATA adapter?
I don't know of a way to detect it, but I haven't looked closely.
-Kevin
On Sun, Mar 04, 2012 at 12:05:14PM -0700, Dave Frodin wrote:
Kevin/Paolo, Our concern was that actual rotating media (e.g. USB-to-SATA adapter) may have problems without the cdb_mode_sense_geom(). I hope to have my hands on one tomorrow to do some testing.
My understanding is that the call was added for QEmu users:
http://www.seabios.org/pipermail/seabios/2011-November/002566.html
-Kevin
Il 04/03/2012 19:49, Kevin O'Connor ha scritto:
The sg_modes command has a "-a" option to dump out all of the supported page codes
- it reports that none of the thumbdrives (tested 9) support page code = 4
- it reports that most of the thumbdrives (tested 9) support page code = 5
- it commented that page code 5 is obsolete
Thanks Dave. I appreciate your detailed analysis.
The call to cdb_mode_sense_geom() was only recently added. I'm inclined to just remove the call. Paolo, is there a use case where having the "physical" chs info is important? SeaBIOS should generate good "virtual" chs info regardless, and the underlying "physical" info is only exported in a couple of places.
MS-DOS doesn't boot if you do not export the physical chs. I can remove it, but it was the best testcase I had for SCSI support.
The simplest solution seems to be to look for page 4 support in page 0x3f.
Paolo
----- Original Message -----
From: "Paolo Bonzini" pbonzini@redhat.com To: "Kevin O'Connor" kevin@koconnor.net Cc: "Dave Frodin" dave@camp.se-eng.com, seabios@seabios.org Sent: Monday, March 5, 2012 1:17:08 AM Subject: Re: Booting from USB thumbdrives, older drives boot, newer drives don't.
Il 04/03/2012 19:49, Kevin O'Connor ha scritto:
The sg_modes command has a "-a" option to dump out all of the supported page codes
- it reports that none of the thumbdrives (tested 9) support
page code = 4
- it reports that most of the thumbdrives (tested 9) support
page code = 5
- it commented that page code 5 is obsolete
Thanks Dave. I appreciate your detailed analysis.
The call to cdb_mode_sense_geom() was only recently added. I'm inclined to just remove the call. Paolo, is there a use case where having the "physical" chs info is important? SeaBIOS should generate good "virtual" chs info regardless, and the underlying "physical" info is only exported in a couple of places.
MS-DOS doesn't boot if you do not export the physical chs. I can remove it, but it was the best testcase I had for SCSI support.
The simplest solution seems to be to look for page 4 support in page 0x3f.
Except that none of the 12 devices I've tested support page 4. There's also a good chance that some of the devices could generate the stall on the page 3f request. That's what led us to thinking we should leave the page 4 query in and just add support to clear the stall.
Paolo
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Dave Frodin -
Fred . -
Kevin O'Connor -
Paolo Bonzini