[Qemu-devel] Re: [PATCH] fix gdbstub support for multiple threads in usermode, v2

[Jan Kiszka <jan.kiszka@siemens.com>]

Paul Brook wrote:
> On Tuesday 16 June 2009, Antti P Miettinen wrote:
>> Paul Brook <paul@codesourcery.com> writes:
>>> Using threads for CPU emulation is just plain wrong.
>>>
>> Could you elaborate a bit? I've sort of assumed that to get reasonable
>> performance out of emulating a parallel target on a parallel host,
> 
> You have taken this comment out of context.
> 
> Exposing multiple CPUs as threads to GDB is incorrect. Each CPU has its own 
> MMU (i.e. address space), so they should be exposed as processes, not threads.

Exposing them as processes isn't fitting either. As stated by Daniel, we
need a "multicore" model (or however we may call it) for gdb.

Until someone "finds" the resources to work on this, qemu's current
approach to expose VCPUs as threads is a pragmatic workaround that
covers many use cases completely and even quite a few more when you deal
with the restrictions properly.

Jan

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