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Re: [Xen-devel] [PATCH 3/4] xen/arm: Implement a dummy debug monitor for ARM32

On 05/02/2014 02:26 PM, Ian Campbell wrote:
> On Fri, 2014-05-02 at 13:53 +0100, Julien Grall wrote:
>> I don't plan to more spend time to write a correct emulation (i.e
>> context switching) to support HW debug.
> I'm not going to ack a patch which causes arm32 to diverge from arm64 in
> this area, especially not when the correct solution (more critical on
> arm64 than arm32) is to properly context switch these registers.

We don't diverge... The Linux HW debug arm32 implementation doesn't
permit to use RAZ/WI on some registers.

Currently arm64 HW debug may or may not work but it won't crash the
guest. It's not the case on arm32. So the current Xen already diverge.

As said earlier, the HW debug is not essential. Writing a proper
emulation will take some time and I don't have time for writing and
testing it correctly.

IHMO, this solution is perfect for Xen 4.4, otherwise Xen 4.4.1 will
breaks support with lots of distribution.

For Xen 4.5, it's intermediate solution to allow guest working correctly
and people playing their shiny distribution on top of Xen. When someone
will care about HW debug, then we will have to support it correctly.


Julien Grall

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