linux-kernel - Set DBGCLAIM when self-host debug is enabled

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Message-ID: <512a30e6cc6877687c10c0f9ccc3c4c5@codeaurora.org>
Date:   Wed, 06 Jan 2021 18:29:53 +0800
From:   tingwei@...eaurora.org
To:     Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Set DBGCLAIM when self-host debug is enabled

Hi Will and Mark,

In recent implementation of save/restore ARM debug registers in EL2/EL3, 
we found
it's necessary to know whether self-host debug is enabled so EL2/EL3 can 
avoid
saving/restoring debug registers but no one is using debug.

In ARM PSCI, it has one option to set DBGCLAIM[1] to 1 to indicate that 
debug is
in use by a self-host debugger. Do you think it's resonable to add this 
to Kernel?

For example, can we set DBGCLAIM[1] to 1 in enable_debug_monitors() and 
clear it
in disable_debug_monitors().

Thanks,
Tingwei

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