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Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support
From: |
Jamie Lokier |
Subject: |
Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support |
Date: |
Sat, 17 Jan 2009 10:03:51 +0000 |
User-agent: |
Mutt/1.5.13 (2006-08-11) |
Paul Brook wrote:
> > a) Modeling cpus as processes buys us nothing compared to threads given
> > the fact that we cannot provide a stable memory mapping to the gdb
> > frontend anyway. (*)
>
> I disagree. The process model fits perfectly. The whole point is
> that each CPU has its own virtual address space. Separate address
> spaces is the fundamental difference between a process and a thread.
That isn't so fundamental.
Distinct CPUs in an OS like Linux have most of the kernel address
space shared between them - except when in special modes like 4G. But
some of the kernel address space is per-CPU.
Threads do not necessarily share the whole virtual address space:
sometimes thread-specific storage is mapped into the same address in
each thread.
In Windows processes, historically it's been possible to have a
mixture of process-specific mapped segments and system-wide shared
segments, which looks more like threads.
Of course there's the no-MMU architectures too.
So the distinction which really matters is, surely, with which model
does GDB behave most usefully with multiple CPUs having their own
MMUs? Does GDB _assume_ all threads have exactly the same address
space, or does GDB allow for threads which have some thread-local
mappings, and therefore always use the correct thread when examining
memory etc.?
-- Jamie
- RE: [Qemu-devel] [RESEND][PATCH] gdbstub: Add vCont support, (continued)
- RE: [Qemu-devel] [RESEND][PATCH] gdbstub: Add vCont support, Krumme, Chris, 2009/01/14
- Re: [Qemu-devel] [RESEND][PATCH] gdbstub: Add vCont support, Anthony Liguori, 2009/01/15
- [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support, Jan Kiszka, 2009/01/15
- Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support, Paul Brook, 2009/01/15
- Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support, Jan Kiszka, 2009/01/16
- Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support, Jan Kiszka, 2009/01/16
- Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support, Paul Brook, 2009/01/16
- Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support, Jan Kiszka, 2009/01/16
- Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support, Daniel Jacobowitz, 2009/01/16
- Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support,
Jamie Lokier <=
- Re: [Qemu-devel] Re: [RESEND][PATCH] gdbstub: Add vCont support, Paul Brook, 2009/01/17