Re: [PATCH 0/3] xenoprof: XSA-313 follow-up

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/04/2020 09:50, Paul Durrant wrote:
>> -----Original Message-----
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>> Sent: 15 April 2020 09:45
>> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
>> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>; George Dunlap 
>> <george.dunlap@xxxxxxxxxx>; Ian Jackson
>> <ian.jackson@xxxxxxxxxxxxx>; Julien Grall <julien@xxxxxxx>; Stefano 
>> Stabellini
>> <sstabellini@xxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Paul Durrant <paul@xxxxxxx>
>> Subject: [PATCH 0/3] xenoprof: XSA-313 follow-up
>>
>> Patch 1 was considered to become part of the XSA, but it was then
>> decided against. The other two are a little bit of cleanup, albeit
>> there's certainly far more room for tidying. Yet then again Paul,
>> in his mail from Mar 13, was asking whether we shouldn't drop
>> xenoprof altogether, at which point cleaning up the code would be
>> wasted effort.
>>
> That's still my opinion. This is a large chunk of (only passively maintained) 
> code which I think is of very limited value (since it relates to an old tool, 
> and it only works for PV domains).

... and yet, noone has bothered getting any other profiler in to a
half-usable state.

You can already Kconfig it out, and yes it is a PITA to use on modern
systems where at the minimum, you need to patch the CPU model whitelist,
and in some cases extend the MSR whitelist in Xen, but at this point
where there are 0 viable alternatives for profiling, removing it would
be a deeply short-sighted move.

~Andrew