From: Viktor Mihajlovski <mihajlov@linux.ibm.com>
To: qemu-devel@nongnu.org
Subject: Re: [PATCH for-5.2 0/6] Continue booting in case the first device is not bootable
Date: Wed, 29 Jul 2020 13:42:05 +0200 [thread overview]
Message-ID: <5c860673-9c0c-79fe-2804-4864856257f5@linux.ibm.com> (raw)
In-Reply-To: <20200728183734.7838-1-thuth@redhat.com>
On 7/28/20 8:37 PM, Thomas Huth wrote:
> If the user did not specify a "bootindex" property, the s390-ccw bios
> tries to find a bootable device on its own. Unfortunately, it alwasy
> stops at the very first device that it can find, no matter whether it's
> bootable or not. That causes some weird behavior, for example while
>
> qemu-system-s390x -hda bootable.qcow2
>
> boots perfectly fine, the bios refuses to work if you just specify
> a virtio-scsi controller in front of it:
>
> qemu-system-s390x -device virtio-scsi -hda bootable.qcow2
>
> Since this is quite uncomfortable and confusing for the users, and
> all major firmwares on other architectures correctly boot in such
> cases, too, let's also try to teach the s390-ccw bios how to boot
> in such cases.
>
> For this, we have to get rid of the various panic()s and IPL_assert()
> statements at the "low-level" function and let the main code handle
> the decision instead whether a boot from a device should fail or not,
> so that the main code can continue searching in case it wants to.
>
Looking at it from an architectural perspective: If an IPL Information
Block specifying the boot device has been set and can be retrieved using
Diagnose 308 it has to be respected, even if the device doesn't contain
a bootable program. The boot has to fail in this case.
I had not the bandwidth to follow all code paths, but I gather that this
is still the case with the series. So one can argue that these changes
are taking care of an undefined situation (real hardware will always
have the IPIB set).
As long as the architecture is not violated, I can live with the
proposed changes. I however would like to point out that this only
covers a corner case (no -boot or -device ..,bootindex specified). A VM
defined and started with libvirt will always specify the boot device.
Please don't create the impression that this patches will lead to the
same behavior as on other platforms. It is still not possible to have an
order list of potential boot devices in an architecture compliant way.
[...]
--
Kind Regards,
Viktor
next prev parent reply other threads:[~2020-07-29 11:43 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 18:37 [PATCH for-5.2 0/6] Continue booting in case the first device is not bootable Thomas Huth
2020-07-28 18:37 ` [PATCH for-5.2 1/6] pc-bios/s390-ccw/Makefile: Compile with -std=gnu99, -fwrapv and -fno-common Thomas Huth
2020-07-29 8:00 ` Claudio Imbrenda
2020-07-29 8:34 ` Cornelia Huck
2020-07-31 7:46 ` Janosch Frank
2020-07-31 7:51 ` Thomas Huth
2020-07-28 18:37 ` [PATCH for-5.2 2/6] pc-bios/s390-ccw: Move ipl-related code from main() into a separate function Thomas Huth
2020-07-29 8:01 ` Claudio Imbrenda
2020-07-29 8:47 ` Cornelia Huck
2020-07-29 11:05 ` Thomas Huth
2020-08-05 9:16 ` Cornelia Huck
2020-08-04 12:52 ` Janosch Frank
2020-07-28 18:37 ` [PATCH for-5.2 3/6] pc-bios/s390-ccw: Move the inner logic of find_subch() to " Thomas Huth
2020-07-29 8:54 ` Cornelia Huck
2020-07-29 11:13 ` Thomas Huth
2020-08-05 9:19 ` Cornelia Huck
2020-08-03 8:46 ` Claudio Imbrenda
2020-08-04 13:24 ` Thomas Huth
2020-08-04 15:30 ` Claudio Imbrenda
2020-08-04 13:26 ` Janosch Frank
2020-07-28 18:37 ` [PATCH for-5.2 4/6] pc-bios/s390-ccw: Do not bail out early if not finding a SCSI disk Thomas Huth
2020-07-29 10:03 ` Cornelia Huck
2020-07-28 18:37 ` [PATCH for-5.2 5/6] pc-bios/s390-ccw: Scan through all boot devices if none has been specified Thomas Huth
2020-08-04 11:06 ` Claudio Imbrenda
2020-08-05 9:36 ` Cornelia Huck
2020-08-05 9:39 ` Thomas Huth
2020-07-28 18:37 ` [PATCH for-5.2 6/6] pc-bios/s390-ccw: Allow booting in case the first virtio-blk disk is bad Thomas Huth
2020-08-05 10:04 ` Cornelia Huck
2020-08-05 10:08 ` Thomas Huth
2020-08-05 10:27 ` Cornelia Huck
2020-07-29 10:10 ` [PATCH for-5.2 0/6] Continue booting in case the first device is not bootable Cornelia Huck
2020-07-29 11:42 ` Viktor Mihajlovski [this message]
2020-07-29 17:17 ` Cornelia Huck
2020-07-30 4:39 ` Thomas Huth
2020-08-04 14:49 ` Janosch Frank
2020-08-04 15:19 ` Thomas Huth
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