Re: [Qemu-devel] [QEMU] [PATCH v5 0/8] Add Qemu to SeaBIOS LCHS interface

From: Kevin Wolf <kwolf@redhat.com>
To: Sam Eiderman <shmuel.eiderman@oracle.com>
Cc: qemu-block@nongnu.org, Arbel Moshe <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 <liran.alon@oracle.com>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Karl Heubaum <karl.heubaum@oracle.com>
Subject: Re: [Qemu-devel] [QEMU] [PATCH v5 0/8] Add Qemu to SeaBIOS LCHS interface
Date: Wed, 17 Jul 2019 21:46:23 +0200	[thread overview]
Message-ID: <20190717194623.GF6471@localhost.localdomain> (raw)
In-Reply-To: <EB5E5E3C-CCA1-4138-9623-89ECA7335F88@oracle.com>

Am 17.07.2019 um 21:03 hat Sam Eiderman geschrieben:
> Gentle ping.

Through which tree is this supposed to go? I feel this is more firmware
interface related than block layer stuff.

Kevin

> > On 8 Jul 2019, at 20:30, Sam Eiderman <shmuel.eiderman@oracle.com> wrote:
> > 
> > Thanks Gerd,
> > 
> > Gentle ping on this.
> > 
> > Sam
> > 
> >> On 1 Jul 2019, at 10:41, Gerd Hoffmann <kraxel@redhat.com> wrote:
> >> 
> >> On Wed, Jun 26, 2019 at 03:39:40PM +0300, Sam Eiderman wrote:
> >>> v1:
> >>> 
> >>> Non-standard logical geometries break under QEMU.
> >>> 
> >>> A virtual disk which contains an operating system which depends on
> >>> logical geometries (consistent values being reported from BIOS INT13
> >>> AH=08) will most likely break under QEMU/SeaBIOS if it has non-standard
> >>> logical geometries - for example 56 SPT (sectors per track).
> >>> No matter what QEMU will guess - SeaBIOS, for large enough disks - will
> >>> use LBA translation, which will report 63 SPT instead.
> >>> 
> >>> In addition we can not enforce SeaBIOS to rely on phyiscal geometries at
> >>> all. A virtio-blk-pci virtual disk with 255 phyiscal heads can not
> >>> report more than 16 physical heads when moved to an IDE controller, the
> >>> ATA spec allows a maximum of 16 heads - this is an artifact of
> >>> virtualization.
> >>> 
> >>> By supplying the logical geometies directly we are able to support such
> >>> "exotic" disks.
> >>> 
> >>> We will use fw_cfg to do just that.
> >>> 
> >>> v2:
> >>> 
> >>> Fix missing parenthesis check in
> >>>   "hd-geo-test: Add tests for lchs override"
> >>> 
> >>> v3:
> >>> 
> >>> * Rename fw_cfg key to "bios-geometry".
> >>> * Remove "extendible" interface.
> >>> * Add cpu_to_le32 fix as Laszlo suggested or big endian hosts
> >>> * Fix last qtest commit - automatic docker tester for some reason does not have qemu-img set
> >>> 
> >>> v4:
> >>> 
> >>> * Change fw_cfg interface from mixed textual/binary to textual only
> >>> 
> >>> v5:
> >>> 
> >>> * Fix line > 80 chars in tests/hd-geo-test.c
> >> 
> >> Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
> >> 
> >> cheers,
> >> Gerd
> >> 
> > 
> 