Re: [PATCH v7 7/8] [DO NOT MERGE] x86/kexec: Add int3 in kexec path for testing

[Ingo Molnar <mingo@kernel.org>]

* David Woodhouse <dwmw2@infradead.org> wrote:

> The exception handler already returns if the exception was int3, but 
> not for anything else. Less so the "print something warm and fuzzy" 
> part; it just does the same register dump. But we could change that.
> 
> I'm less keen on making it unconditional though. Kexec is a 
> performance-critical path when every millisecond is perceived as 
> guest steal time, and the serial output should only happen in 
> production if something goes *wrong*.
> 
> And besides, most kexec users don't have early_printk enabled anyway 
> so if we break them, this idea doesn't help.

So this check would only cause any real overhead if serial debugging is 
enabled - in which case there's already substantial overhead due to the 
serial console overhead (virtual or otherwise).

As to not printing anything unless the early serial console is enabled 
- that's fine, we'd still *break* if something doesn't work in this 
code path, so at least the exception handling machinery is kept 
well-tested. :-)

Thanks,

	Ingo