Subject: Re: [PATCH v2] arm64:kgdb: Fix kernel single-stepping

From: Marc Zyngier <[email-masked]>
Date: Thu, 20 Feb 2020 14:21:36 +0000

On 2020-02-19 15:24, [email-masked] wrote:
> From: Corey Minyard <[email-masked]>

[...]

> After studying the EL0 handling for this, I realized an issue with 
> using
> MDSCR to check if single step is enabled: it can be expensive on a VM.
> So check the task flag first to see if single step is enabled.  Then
> check MDSCR if the task flag is set.

Very tangential remark: I'd really like people *not* to try and optimize
Linux based on the behaviour of a hypervisor. In general, reading a
system register is fast, and the fact that it traps on a given 
hypervisor
at some point may not be true in the future, nor be a valid assumption
across hypervisors.

         M.
-- 
Jazz is not dead. It just smells funny...

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