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

[Marc Zyngier]

On 2020-02-19 15:24, minyard@xxxxxxx wrote:
> From: Corey Minyard <cminyard@xxxxxxxxxx>

[...]

> 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...