From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37213) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1asy9e-0008BR-Dh for qemu-devel@nongnu.org; Wed, 20 Apr 2016 15:51:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1asy9b-0006T7-7C for qemu-devel@nongnu.org; Wed, 20 Apr 2016 15:51:18 -0400 Received: from mail-wm0-x234.google.com ([2a00:1450:400c:c09::234]:35837) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1asy9b-0006Sx-13 for qemu-devel@nongnu.org; Wed, 20 Apr 2016 15:51:15 -0400 Received: by mail-wm0-x234.google.com with SMTP id e201so62891525wme.0 for ; Wed, 20 Apr 2016 12:51:14 -0700 (PDT) References: <1460044433-19282-1-git-send-email-sergey.fedorov@linaro.org> <1460044433-19282-9-git-send-email-sergey.fedorov@linaro.org> <87k2jsv0pv.fsf@linaro.org> <57179B80.9050800@twiddle.net> <87ega0uolz.fsf@linaro.org> <5717D130.8090100@twiddle.net> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <5717D130.8090100@twiddle.net> Date: Wed, 20 Apr 2016 20:51:12 +0100 Message-ID: <878u08uki7.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH 08/11] tcg/aarch64: Make direct jump patching thread-safe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: Sergey Fedorov , qemu-devel@nongnu.org, Sergey Fedorov , Paolo Bonzini , Peter Crosthwaite , Claudio Fontana , qemu-arm@nongnu.org Richard Henderson writes: > On 04/20/2016 11:22 AM, Alex Bennée wrote: >> >> Richard Henderson writes: >> >>> On 04/20/2016 07:01 AM, Alex Bennée wrote: >>>> >>>> Sergey Fedorov writes: >>>> >>>>> From: Sergey Fedorov >>>>> >>>>> Ensure direct jump patching in AArch64 is atomic by using >>>>> atomic_read()/atomic_set() for code patching. >>>>> >>>>> Signed-off-by: Sergey Fedorov >>>>> Signed-off-by: Sergey Fedorov >>>>> --- >>>>> tcg/aarch64/tcg-target.inc.c | 14 +++++++++++++- >>>>> 1 file changed, 13 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/tcg/aarch64/tcg-target.inc.c b/tcg/aarch64/tcg-target.inc.c >>>>> index 0ed10a974121..15fdebec921f 100644 >>>>> --- a/tcg/aarch64/tcg-target.inc.c >>>>> +++ b/tcg/aarch64/tcg-target.inc.c >>>>> @@ -73,6 +73,18 @@ static inline void reloc_pc26(tcg_insn_unit *code_ptr, tcg_insn_unit *target) >>>>> *code_ptr = deposit32(*code_ptr, 0, 26, offset); >>>>> } >>>>> >>>>> +static inline void reloc_pc26_atomic(tcg_insn_unit *code_ptr, >>>>> + tcg_insn_unit *target) >>>>> +{ >>>>> + ptrdiff_t offset = target - code_ptr; >>>>> + tcg_insn_unit insn; >>>>> + assert(offset == sextract64(offset, 0, 26)); >>>>> + /* read instruction, mask away previous PC_REL26 parameter contents, >>>>> + set the proper offset, then write back the instruction. */ >>>> >>>> This comment could be moved from here and reloc_pc26 and made common for >>>> the two following functions. >>> >>> There's a significant amount of cleanup that ought to happen here, now that >>> we're not re-translating TBs. I don't know if Sergey should be gated >>> on that. >> >> Is this stuff already in the works? Otherwise we are trying to get >> pre-cursors to MTTCG into the code (once the tree re-opens) to keep the >> main diff down. This also is beneficial for linux-user stuff. > > We're talking past one another. > > No, it's not yet in the works. I'm saying that this patch set should not wait > for it. Thus I don't care if what he adds here is a little messy; we'll clean > it all up at once later. Thus don't bother refactoring reloc_pc26 and > reloc_pc26_atomic. Ahh OK, cool ;-) > > > r~ -- Alex Bennée