need to cope with Arndale's inability to handle Thumb2 KVM guest kernels

Bug #1133357 reported by Peter Maydell on 2013-02-26
16
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Arndale
Won't Fix
Undecided
Unassigned
Linaro KVM Development
Undecided
Unassigned
linaro-landing-team-samsung
Won't Fix
High
Unassigned

Bug Description

The revision of the A15 on the Arndale boards cannot handle Thumb2 KVM guest kernels (Thumb2 guest userspace is fine). This is unfortunately a hardware issue which cannot be worked around.

 * We need to be doing KVM testing on more than just Arndale (ie TC2 as well) to cover all the use cases
 * We need to have some ARM-kernel test cases so we can do testing on Arndale (worth doing since it's probably going to be a popular board)
 * We should make sure "thumb2 guest kernels on arndale won't work" is documented somewhere useful (in whatever the landing team's equivalent of releasenotes?) to avoid a flood of user confusion

Tushar Behera (tusharbehera) wrote :

We get a kernel panic while rebooting if THUMB2 support is enabled in kernel. Looking at the bug description, is this an issue with the A15 revision or something wrong with Arndale kernel?

On 28 February 2013 07:04, Tushar Behera <email address hidden> wrote:
> We get a kernel panic while rebooting if THUMB2 support is enabled in
> kernel. Looking at the bug description, is this an issue with the A15
> revision or something wrong with Arndale kernel?

The A15 version used on Arndale has a known and documented bug that
prevents the use of MMIO using Thumb2 code.

Anmar Oueja (anmar) on 2013-03-07
Changed in linaro-landing-team-samsung:
importance: Undecided → High
Tushar Behera (tusharbehera) wrote :

Given that this is a hardware bug, what is the resolution for this?

Changed in linaro-landing-team-samsung:
status: New → Confirmed
Peter Maydell (pmaydell) wrote :

"We get a kernel panic while rebooting if THUMB2 support is enabled in kernel." -- just to be clear, you mean while booting your host kernel, or your KVM guest kernel?

"what is the resolution for this?" -- my suggestions are described in the initial bug report text.

Tushar Behera (tusharbehera) wrote :

On 03/07/2013 11:38 AM, Peter Maydell wrote:
> "We get a kernel panic while rebooting if THUMB2 support is enabled in
> kernel." -- just to be clear, you mean while booting your host kernel,
> or your KVM guest kernel?

Yes, the host kernel.

--
Tushar Behera

Peter Maydell (pmaydell) wrote :

OK, if your host kernel crashes on boot or reboot then that is a different bug. The symptoms of this bug are : host kernel functions perfectly fine, but guest KVM kernel crashes/misbehaves if it is compiled for Thumb2.

Please file a fresh LP bug against the appropriate component for the issues you are seeing.

Anmar Oueja (anmar) wrote :

I am closing this bug as won't fix since it is a HW issue that we can't do anything about (confirmed with ARM).

Tushar: Please open a separate bug for the host kernel.

Changed in linaro-landing-team-samsung:
status: Confirmed → Won't Fix
Changed in arndale:
status: New → Won't Fix
Tushar Behera (tusharbehera) wrote :

On 03/08/2013 04:55 PM, Tushar Behera wrote:
> The issue was because of a hardcoded WFI instruction. Following patch
> fixes the issue.
Just to clarify, this is regarding the host kernel reboot issue with
THUMB2 kernel.

--
Tushar Behera

Christoffer Dall (cdall) wrote :

Changed to invalid or linaro-kvm: this is not a bug in KVM but a hardware bug we can't do much about.

Changed in linaro-kvm:
status: New → Confirmed
status: Confirmed → Invalid
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