From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B6B5C3A59F for ; Thu, 29 Aug 2019 23:49:29 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 15BF42166E for ; Thu, 29 Aug 2019 23:49:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ECXuiYAk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 15BF42166E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=wKDAf6V6m4NbXtnPwFRB35np7CM+vAp24qjnWlxwi2w=; b=ECXuiYAkrm6U2O e2i/+khwVaDmZvJhNjZ7HULPMergmivQfXvuZqtNK4+nQaKNs3APYW9IDhL2kLrAqEbNH4CPv8Cbe Sp4m673GkQltM+yIY1exwvOzYe0Z8J6Hk3mERV27jGtzXuNI+Q5w2CJGH3scYLLUsucS30D+SHOlP Qcms6ybMLiu1kwmvUc0d/m9i+/C5HrzxIJYaA20i977I0xuAjGX1cWQh4zbaqUVbjGfkEDux0ZPgF PpT9UqxxvuqOnIAQVpX/6eT5sY4/9S+nTJjZ3cY56eTLR7zekNswXjFROA3jFd1MSxDHghxvZHiZD i901iOpuU/ufazD/hEHA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i3UAL-0007xS-UZ; Thu, 29 Aug 2019 23:49:22 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i3UAI-0007x9-2A for linux-arm-kernel@lists.infradead.org; Thu, 29 Aug 2019 23:49:19 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 620EF337; Thu, 29 Aug 2019 16:49:17 -0700 (PDT) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CA6A03F718; Thu, 29 Aug 2019 16:49:16 -0700 (PDT) Date: Fri, 30 Aug 2019 00:49:15 +0100 From: Andrew Murray To: Will Deacon Subject: Re: [PATCH v5 10/10] arm64: atomics: Use K constraint when toolchain appears to support it Message-ID: <20190829234914.GQ14582@e119886-lin.cambridge.arm.com> References: <20190829154834.26547-1-will@kernel.org> <20190829154834.26547-11-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190829154834.26547-11-will@kernel.org> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190829_164918_196661_B419D7D4 X-CRM114-Status: GOOD ( 20.24 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, peterz@infradead.org, catalin.marinas@arm.com, ndesaulniers@google.com, Ard.Biesheuvel@arm.com, natechancellor@gmail.com, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Aug 29, 2019 at 04:48:34PM +0100, Will Deacon wrote: > The 'K' constraint is a documented AArch64 machine constraint supported > by GCC for matching integer constants that can be used with a 32-bit > logical instruction. Unfortunately, some released compilers erroneously > accept the immediate '4294967295' for this constraint, which is later > refused by GAS at assembly time. This had led us to avoid the use of > the 'K' constraint altogether. > > Instead, detect whether the compiler is up to the job when building the > kernel and pass the 'K' constraint to our 32-bit atomic macros when it > appears to be supported. > > Signed-off-by: Will Deacon See my comments within this email thread, but for this patch as it is: Reviewed-by: Andrew Murray > --- > arch/arm64/Makefile | 9 ++++++- > arch/arm64/include/asm/atomic_ll_sc.h | 47 +++++++++++++++++++++++------------ > 2 files changed, 39 insertions(+), 17 deletions(-) > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 61de992bbea3..0cef056b5fb1 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -39,6 +39,12 @@ $(warning LSE atomics not supported by binutils) > endif > endif > > +cc_has_k_constraint := $(call try-run,echo \ > + 'int main(void) { \ > + asm volatile("and w0, w0, %w0" :: "K" (4294967295)); \ > + return 0; \ > + }' | $(CC) -S -x c -o "$$TMP" -,,-DCONFIG_CC_HAS_K_CONSTRAINT=1) > + > ifeq ($(CONFIG_ARM64), y) > brokengasinst := $(call as-instr,1:\n.inst 0\n.rept . - 1b\n\nnop\n.endr\n,,-DCONFIG_BROKEN_GAS_INST=1) > > @@ -63,7 +69,8 @@ ifeq ($(CONFIG_GENERIC_COMPAT_VDSO), y) > endif > endif > > -KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst) $(compat_vdso) > +KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst) \ > + $(compat_vdso) $(cc_has_k_constraint) > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > KBUILD_CFLAGS += $(call cc-disable-warning, psabi) > KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) $(compat_vdso) > diff --git a/arch/arm64/include/asm/atomic_ll_sc.h b/arch/arm64/include/asm/atomic_ll_sc.h > index 95091f72228b..7fa042f5444e 100644 > --- a/arch/arm64/include/asm/atomic_ll_sc.h > +++ b/arch/arm64/include/asm/atomic_ll_sc.h > @@ -23,6 +23,10 @@ asm_ops "\n" \ > #define __LL_SC_FALLBACK(asm_ops) asm_ops > #endif > > +#ifndef CONFIG_CC_HAS_K_CONSTRAINT > +#define K > +#endif > + > /* > * AArch64 UP and SMP safe atomic ops. We use load exclusive and > * store exclusive to ensure that these are atomic. We may loop > @@ -113,10 +117,15 @@ ATOMIC_OPS(sub, sub, J) > ATOMIC_FETCH_OP (_acquire, , a, , "memory", __VA_ARGS__)\ > ATOMIC_FETCH_OP (_release, , , l, "memory", __VA_ARGS__) > > -ATOMIC_OPS(and, and, ) > +ATOMIC_OPS(and, and, K) > +ATOMIC_OPS(or, orr, K) > +ATOMIC_OPS(xor, eor, K) > +/* > + * GAS converts the mysterious and undocumented BIC (immediate) alias to > + * an AND (immediate) instruction with the immediate inverted. We don't > + * have a constraint for this, so fall back to register. > + */ > ATOMIC_OPS(andnot, bic, ) > -ATOMIC_OPS(or, orr, ) > -ATOMIC_OPS(xor, eor, ) > > #undef ATOMIC_OPS > #undef ATOMIC_FETCH_OP > @@ -208,9 +217,14 @@ ATOMIC64_OPS(sub, sub, J) > ATOMIC64_FETCH_OP (_release,, , l, "memory", __VA_ARGS__) > > ATOMIC64_OPS(and, and, L) > -ATOMIC64_OPS(andnot, bic, ) > ATOMIC64_OPS(or, orr, L) > ATOMIC64_OPS(xor, eor, L) > +/* > + * GAS converts the mysterious and undocumented BIC (immediate) alias to > + * an AND (immediate) instruction with the immediate inverted. We don't > + * have a constraint for this, so fall back to register. > + */ > +ATOMIC64_OPS(andnot, bic, ) > > #undef ATOMIC64_OPS > #undef ATOMIC64_FETCH_OP > @@ -280,21 +294,21 @@ __ll_sc__cmpxchg_case_##name##sz(volatile void *ptr, \ > * handle the 'K' constraint for the value 4294967295 - thus we use no > * constraint for 32 bit operations. > */ > -__CMPXCHG_CASE(w, b, , 8, , , , , ) > -__CMPXCHG_CASE(w, h, , 16, , , , , ) > -__CMPXCHG_CASE(w, , , 32, , , , , ) > +__CMPXCHG_CASE(w, b, , 8, , , , , K) > +__CMPXCHG_CASE(w, h, , 16, , , , , K) > +__CMPXCHG_CASE(w, , , 32, , , , , K) > __CMPXCHG_CASE( , , , 64, , , , , L) > -__CMPXCHG_CASE(w, b, acq_, 8, , a, , "memory", ) > -__CMPXCHG_CASE(w, h, acq_, 16, , a, , "memory", ) > -__CMPXCHG_CASE(w, , acq_, 32, , a, , "memory", ) > +__CMPXCHG_CASE(w, b, acq_, 8, , a, , "memory", K) > +__CMPXCHG_CASE(w, h, acq_, 16, , a, , "memory", K) > +__CMPXCHG_CASE(w, , acq_, 32, , a, , "memory", K) > __CMPXCHG_CASE( , , acq_, 64, , a, , "memory", L) > -__CMPXCHG_CASE(w, b, rel_, 8, , , l, "memory", ) > -__CMPXCHG_CASE(w, h, rel_, 16, , , l, "memory", ) > -__CMPXCHG_CASE(w, , rel_, 32, , , l, "memory", ) > +__CMPXCHG_CASE(w, b, rel_, 8, , , l, "memory", K) > +__CMPXCHG_CASE(w, h, rel_, 16, , , l, "memory", K) > +__CMPXCHG_CASE(w, , rel_, 32, , , l, "memory", K) > __CMPXCHG_CASE( , , rel_, 64, , , l, "memory", L) > -__CMPXCHG_CASE(w, b, mb_, 8, dmb ish, , l, "memory", ) > -__CMPXCHG_CASE(w, h, mb_, 16, dmb ish, , l, "memory", ) > -__CMPXCHG_CASE(w, , mb_, 32, dmb ish, , l, "memory", ) > +__CMPXCHG_CASE(w, b, mb_, 8, dmb ish, , l, "memory", K) > +__CMPXCHG_CASE(w, h, mb_, 16, dmb ish, , l, "memory", K) > +__CMPXCHG_CASE(w, , mb_, 32, dmb ish, , l, "memory", K) > __CMPXCHG_CASE( , , mb_, 64, dmb ish, , l, "memory", L) > > #undef __CMPXCHG_CASE > @@ -332,5 +346,6 @@ __CMPXCHG_DBL( , , , ) > __CMPXCHG_DBL(_mb, dmb ish, l, "memory") > > #undef __CMPXCHG_DBL > +#undef K > > #endif /* __ASM_ATOMIC_LL_SC_H */ > -- > 2.11.0 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel