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References: <1460044433-19282-1-git-send-email-sergey.fedorov@linaro.org>
	<1460044433-19282-11-git-send-email-sergey.fedorov@linaro.org>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <5706846B.2060804@redhat.com>
Date: Thu, 7 Apr 2016 18:01:47 +0200
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Subject: Re: [Qemu-devel] [PATCH 10/11] tcg/mips: Make direct jump patching
	thread-safe
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To: Sergey Fedorov <sergey.fedorov@linaro.org>, qemu-devel@nongnu.org
Cc: Sergey Fedorov <serge.fdrv@gmail.com>, Richard Henderson <rth@twiddle.net>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Aurelien Jarno <aurelien@aurel32.net>, Peter Crosthwaite <crosthwaite.peter@gmail.com>



On 07/04/2016 17:53, Sergey Fedorov wrote:
> Ensure direct jump patching in MIPS is atomic by using
> atomic_read()/atomic_set() for code patching.
> 
> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
> ---
>  tcg/mips/tcg-target.inc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tcg/mips/tcg-target.inc.c b/tcg/mips/tcg-target.inc.c
> index 682e19897db0..e65835d2096b 100644
> --- a/tcg/mips/tcg-target.inc.c
> +++ b/tcg/mips/tcg-target.inc.c
> @@ -1886,6 +1886,7 @@ static void tcg_target_init(TCGContext *s)
>  void tb_set_jmp_target1(uintptr_t jmp_addr, uintptr_t addr)
>  {
>      uint32_t *ptr = (uint32_t *)jmp_addr;
> -    *ptr = deposit32(*ptr, 0, 26, addr >> 2);
> +    uint32_t insn = atomic_read(ptr);
> +    atomic_write(ptr, deposit32(insn, 0, 26, addr >> 2));

Oops. :)

Paolo

>      flush_icache_range(jmp_addr, jmp_addr + 4);
>  }