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From: Gerd Hoffmann <kraxel@redhat.com>
To: Sam Eiderman <shmuel.eiderman@oracle.com>
Cc: kwolf@redhat.com, qemu-block@nongnu.org, arbel.moshe@oracle.com,
	seabios@seabios.org, QEMU <qemu-devel@nongnu.org>,
	Max Reitz <mreitz@redhat.com>,
	Kevin O'Connor <kevin@koconnor.net>,
	liran.alon@oracle.com, Karl Heubaum <karl.heubaum@oracle.com>
Subject: Re: [Qemu-devel] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface
Date: Fri, 14 Jun 2019 06:43:10 +0200	[thread overview]
Message-ID: <20190614044310.wxnkwxagr23d5cbt@sirius.home.kraxel.org> (raw)
In-Reply-To: <730C65DE-A9B4-4553-B6A0-7A3B81A1FA12@oracle.com>

  Hi,

> Can there be a guest that will fail the MBR in such a way? Yes.
> Look at the following MBR partition table of a Windows XP guest in our production
> environment:
> 
> Disk size in sectors: 16777216
> 
> Binary (only one partition 16 bytes): 80 01 01 00 07 fe ff ff 3f 00 00 00 d5 ea ff 00
> Start: (0, 1, 1, 63)
> End: (1023, 254, 63, 16771859)
> 
> As can be easily seen, any MBR guessing algorithm should guess:
> 
> 	255 heads (since a value of 254 appears), 63 spt (since a value of 63 appears)
> 
> Turns out that this image does not work with 255, 63 but actually requires
> 
> 	16 heads, 63 spt
> 
> to boot.
> 
> So relying on MBR partitions alone is not always enough and sometimes manual intervention
> is required.

Ok, given that seabios has no setup any manual configuration needs to be done via qemu.

But why do we need a new interface for that?  IDE can pass the geometry
to the guest.  virtio-blk has support too (VIRTIO_BLK_F_GEOMETRY).
Likewise scsi (MODE_PAGE_HD_GEOMETRY).  So this should be doable without
any qemu changes.

cheers,
  Gerd



  reply	other threads:[~2019-06-14  4:49 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-12 11:59 [Qemu-devel] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface Sam Eiderman
2019-06-12 11:59 ` [Qemu-devel] [QEMU] [PATCH v2 1/8] block: Refactor macros - fix tabbing Sam Eiderman
2019-06-12 11:59 ` [Qemu-devel] [QEMU] [PATCH v2 2/8] block: Support providing LCHS from user Sam Eiderman
2019-06-12 11:59 ` [Qemu-devel] [QEMU] [PATCH v2 3/8] bootdevice: Add interface to gather LCHS Sam Eiderman
2019-06-12 11:59 ` [Qemu-devel] [QEMU] [PATCH v2 4/8] scsi: Propagate unrealize() callback to scsi-hd Sam Eiderman
2019-06-12 11:59 ` [Qemu-devel] [QEMU] [PATCH v2 5/8] bootdevice: Gather LCHS from all relevant devices Sam Eiderman
2019-06-12 11:59 ` [Qemu-devel] [QEMU] [PATCH v2 6/8] bootdevice: Refactor get_boot_devices_list Sam Eiderman
2019-06-12 11:59 ` [Qemu-devel] [QEMU] [PATCH v2 7/8] bootdevice: FW_CFG interface for LCHS values Sam Eiderman
2019-06-17  7:20   ` Gerd Hoffmann
2019-06-17  7:36     ` Sam Eiderman
2019-06-17  8:38       ` Gerd Hoffmann
2019-06-17 10:08         ` Sam Eiderman
2019-06-17 14:48       ` Kevin O'Connor
2019-06-17 15:13         ` Sam Eiderman
2019-06-12 11:59 ` [Qemu-devel] [QEMU] [PATCH v2 8/8] hd-geo-test: Add tests for lchs override Sam Eiderman
2019-06-12 12:33 ` [Qemu-devel] [SeaBIOS] [QEMU] [PATCH v2 0/8] Add Qemu to SeaBIOS LCHS interface no-reply
2019-06-12 13:06 ` [Qemu-devel] " Gerd Hoffmann
2019-06-12 13:30   ` Sam Eiderman
2019-06-12 19:18     ` Gerd Hoffmann
2019-06-13  7:41       ` Sam Eiderman
2019-06-13  7:44         ` Sam Eiderman
2019-06-13  9:38         ` Gerd Hoffmann
2019-06-13 11:45           ` Sam Eiderman
2019-06-14  4:43             ` Gerd Hoffmann [this message]
2019-06-14  9:37               ` Sam Eiderman
2019-06-17  6:50                 ` Gerd Hoffmann
2019-06-17  7:59                   ` Sam Eiderman
2019-06-12 13:51 ` [Qemu-devel] [SeaBIOS] " no-reply

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