From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: mttcg@greensocs.com, "QEMU Developers" <qemu-devel@nongnu.org>,
"KONRAD Frédéric" <fred.konrad@greensocs.com>
Subject: Re: [Qemu-devel] [PATCH 05/10] cpu-exec: elide more icount code if CONFIG_USER_ONLY
Date: Sat, 29 Aug 2015 09:07:58 +0200 [thread overview]
Message-ID: <55E15A4E.6080009@redhat.com> (raw)
In-Reply-To: <CAFEAcA8ob8A+Sa4ytM=xOadQ26ezr6EhzEy=cGkP9U32MSYBZg@mail.gmail.com>
On 28/08/2015 16:56, Peter Maydell wrote:
> What's the rationale for this? Mostly we prefer not to
> add ifdefs in code if we can get away with compiling it for
> both cases, even if the resulting code isn't used.
True. The rationale is three-fold:
1) It makes sense to abort if TB_EXIT_ICOUNT_EXPIRED is returned from
user-mode emulation TCG code. Then you need to either leave the
unreachable code after abort() or #ifdef cpu_exec_nocache out.
2) Dually, cpu_exec_nocache's future locking requirements (take tb_lock,
mostly) are not yet respected as of this patch. Marking the function as
#ifdef CONFIG_SOFTMMU explains why. Once you do that, you have to
abort() either in cpu_exec_nocache or in the caller.
Reason (2) is stronger for me. You mentioned a few times your hope that
MTTCG would lead to more correct and more documented thread support in
user-mode emulation, and I think this patch does improve the
documentation slightly.
Paolo
next prev parent reply other threads:[~2015-08-29 7:08 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-12 16:40 [Qemu-devel] [PATCH 00/10] translate-all.c thread-safety Paolo Bonzini
2015-08-12 16:40 ` [Qemu-devel] [PATCH 01/10] cpus: protect work list with work_mutex Paolo Bonzini
2015-08-28 14:33 ` Peter Maydell
2015-08-12 16:40 ` [Qemu-devel] [PATCH 02/10] cpus: remove tcg_halt_cond global variable Paolo Bonzini
2015-08-13 13:05 ` Frederic Konrad
2015-08-13 13:08 ` Paolo Bonzini
2015-08-13 13:19 ` Frederic Konrad
2015-08-28 14:36 ` Peter Maydell
2015-08-29 6:52 ` Paolo Bonzini
2015-08-12 16:40 ` [Qemu-devel] [PATCH 03/10] replace spinlock by QemuMutex Paolo Bonzini
2015-08-13 12:17 ` Frederic Konrad
2015-08-13 13:12 ` Paolo Bonzini
2015-08-13 13:21 ` Frederic Konrad
2015-08-28 14:49 ` Peter Maydell
2015-08-28 14:53 ` Frederic Konrad
2015-08-29 6:51 ` Paolo Bonzini
2015-08-12 16:40 ` [Qemu-devel] [PATCH 04/10] exec-all: remove non-TCG stuff from exec-all.h header Paolo Bonzini
2015-08-28 14:53 ` Peter Maydell
2015-08-29 6:55 ` Paolo Bonzini
2015-08-12 16:40 ` [Qemu-devel] [PATCH 05/10] cpu-exec: elide more icount code if CONFIG_USER_ONLY Paolo Bonzini
2015-08-13 13:14 ` Frederic Konrad
2015-08-13 14:06 ` Paolo Bonzini
2015-08-28 14:56 ` Peter Maydell
2015-08-29 7:07 ` Paolo Bonzini [this message]
2015-08-12 16:40 ` [Qemu-devel] [PATCH 06/10] tcg: code_bitmap is not used by user-mode emulation Paolo Bonzini
2015-08-28 14:57 ` Peter Maydell
2015-08-29 7:13 ` Paolo Bonzini
2015-08-12 16:40 ` [Qemu-devel] [PATCH 07/10] tcg: comment on which functions have to be called with mmap_lock held Paolo Bonzini
2015-08-28 15:33 ` Peter Maydell
2015-08-29 6:57 ` Paolo Bonzini
2015-08-12 16:41 ` [Qemu-devel] [PATCH 08/10] tcg: add memory barriers in page_find_alloc accesses Paolo Bonzini
2015-08-12 20:37 ` Emilio G. Cota
2015-08-13 8:13 ` Paolo Bonzini
2015-08-13 19:50 ` Emilio G. Cota
2015-08-28 15:40 ` Peter Maydell
2015-08-29 6:58 ` Paolo Bonzini
2015-08-12 16:41 ` [Qemu-devel] [PATCH 09/10] exec: make mmap_lock/mmap_unlock globally available Paolo Bonzini
2015-08-28 15:42 ` Peter Maydell
2015-08-12 16:41 ` [Qemu-devel] [PATCH 10/10] cpu-exec: fix lock hierarchy for user-mode emulation Paolo Bonzini
2015-08-28 15:59 ` Peter Maydell
2015-08-12 16:41 ` [Qemu-devel] [PATCH 11/10] tcg: comment on which functions have to be called with tb_lock held Paolo Bonzini
2015-08-13 12:51 ` Frederic Konrad
2015-08-13 12:59 ` Paolo Bonzini
2015-08-13 13:32 ` Frederic Konrad
2015-08-13 14:39 ` Paolo Bonzini
2015-08-13 15:32 ` Peter Maydell
2015-08-13 16:20 ` Paolo Bonzini
2015-08-12 16:41 ` [Qemu-devel] [PATCH 12/10] tcg: protect TBContext with tb_lock Paolo Bonzini
2015-08-13 12:57 ` Frederic Konrad
2015-08-13 13:01 ` Paolo Bonzini
2015-08-13 13:04 ` Frederic Konrad
2015-08-14 9:26 ` [Qemu-devel] [PATCH 00/10] translate-all.c thread-safety Frederic Konrad
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