Re: [Qemu-devel] [PATCH 03/11] target/sh4: Handle user-space atomics

From: Aurelien Jarno <aurelien@aurel32.net>
To: Richard Henderson <rth@twiddle.net>
Cc: qemu-devel@nongnu.org, bruno@clisp.org
Subject: Re: [Qemu-devel] [PATCH 03/11] target/sh4: Handle user-space atomics
Date: Thu, 6 Jul 2017 17:50:51 +0200	[thread overview]
Message-ID: <20170706155051.placknk6o3uismoj@aurel32.net> (raw)
In-Reply-To: <20170706002401.10507-4-rth@twiddle.net>

On 2017-07-05 14:23, Richard Henderson wrote:
> For uniprocessors, SH4 uses optimistic restartable atomic sequences.
> Upon an interrupt, a real kernel would simply notice magic values in
> the registers and reset the PC to the start of the sequence.
> 
> For QEMU, we cannot do this in quite the same way.  Instead, we notice
> the normal start of such a sequence (mov #-x,r15), and start a new TB
> that can be executed under cpu_exec_step_atomic.
> 
> Reported-by: Bruno Haible  <bruno@clisp.org>
> LP: https://bugs.launchpad.net/bugs/1701971
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  target/sh4/cpu.h       |  21 ++++++--
>  target/sh4/helper.h    |   1 +
>  target/sh4/op_helper.c |   6 +++
>  target/sh4/translate.c | 137 +++++++++++++++++++++++++++++++++++++++++++------
>  4 files changed, 147 insertions(+), 18 deletions(-)

I haven't reviewed this patch in details, but note that it breaks
booting a system under qemu-system.

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net