Re: [Qemu-devel] [PATCH 03/11] tci: Make direct jump patching thread-safe

From: Sergey Fedorov <serge.fdrv@gmail.com>
To: "Alex Bennée" <alex.bennee@linaro.org>,
	"Sergey Fedorov" <sergey.fedorov@linaro.org>
Cc: qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
	Peter Crosthwaite <crosthwaite.peter@gmail.com>,
	Richard Henderson <rth@twiddle.net>, Stefan Weil <sw@weilnetz.de>
Subject: Re: [Qemu-devel] [PATCH 03/11] tci: Make direct jump patching thread-safe
Date: Wed, 20 Apr 2016 14:40:16 +0300	[thread overview]
Message-ID: <57176AA0.2030803@gmail.com> (raw)
In-Reply-To: <87shygvcot.fsf@linaro.org>

On 20/04/16 12:42, Alex Bennée wrote:
> Sergey Fedorov <sergey.fedorov@linaro.org> writes:
>> diff --git a/tcg/tci/tcg-target.inc.c b/tcg/tci/tcg-target.inc.c
>> index 4afe4d7a8d59..7e6180e62898 100644
>> --- a/tcg/tci/tcg-target.inc.c
>> +++ b/tcg/tci/tcg-target.inc.c
>> @@ -556,6 +556,8 @@ static void tcg_out_op(TCGContext *s, TCGOpcode opc, const TCGArg *args,
>>          if (s->tb_jmp_offset) {
>>              /* Direct jump method. */
>>              assert(args[0] < ARRAY_SIZE(s->tb_jmp_offset));
>> +            /* Align for atomic patching and thread safety */
>> +            s->code_ptr = (uint8_t *)(((uintptr_t)s->code_ptr + 3) &
>> ~3);
> Seeing this pattern is being used over and over again I wonder if we
> should have some utility helper functions for this? Perhaps we should
> steal the kernels ALIGN macros?

Good point, really. I see such a macro in hw/display/qxl.c and
kvm-all.c. It'd be better a common definition. Any idea of where to put it?

Kind regards,
Sergey