From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 46188167DBD for ; Wed, 29 May 2024 11:14:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716981271; cv=none; b=LaBHki1f56Bsq9LJofOBEbk1S6sQxetJF7Os6jepZxm/s3dBuTwl+8vY+NK/5Edy3akPslWUFpK+dOL+Cneoca7viZsWFRuB4dxp9dalZ0JzkU+tnDbBDuoPXRHqCbaYLlW2x0hCWunmMJSLz2g5PdcqDQILWDbRY/XkHKUmOV4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716981271; c=relaxed/simple; bh=2iOnoOqaH1ns/TUfviGdLnP1bua85YpsSllsgPuidfU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QntT4UBNk5sdqdccR4U7YQttv8rn4ZFRaEBbQGerGGN0EUwkZWhTo/HA20t8D+Nrx6iOjBgU8oKNT00VR2lub8dNOgyMk2k1OU9iCBPgRylqRUX/Z8hlS8vLHe7yQ3nmZsCT1FwJk2SFX07N+n+YWJ868Zib+V1iNsTd4vmbDKo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 AD5E2339; Wed, 29 May 2024 04:14:51 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B335E3F792; Wed, 29 May 2024 04:14:25 -0700 (PDT) Date: Wed, 29 May 2024 12:14:22 +0100 From: Mark Rutland To: Arnd Bergmann Cc: Catalin Marinas , Will Deacon , Jason Gunthorpe , Arnd Bergmann , Valentin Schneider , Baoquan He , Peter Zijlstra , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64/io: add constant-argument check Message-ID: References: <20240528120844.3523915-1-arnd@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240528120844.3523915-1-arnd@kernel.org> On Tue, May 28, 2024 at 02:08:38PM +0200, Arnd Bergmann wrote: > From: Arnd Bergmann > > In some configurations __const_iowrite32_copy() does not get inlined > and gcc runs into the BUILD_BUG(): > > In file included from : > In function '__const_memcpy_toio_aligned32', > inlined from '__const_iowrite32_copy' at arch/arm64/include/asm/io.h:203:3, > inlined from '__const_iowrite32_copy' at arch/arm64/include/asm/io.h:199:20: > include/linux/compiler_types.h:487:45: error: call to '__compiletime_assert_538' declared with attribute error: BUILD_BUG failed > 487 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > | ^ > include/linux/compiler_types.h:468:25: note: in definition of macro '__compiletime_assert' > 468 | prefix ## suffix(); \ > | ^~~~~~ > include/linux/compiler_types.h:487:9: note: in expansion of macro '_compiletime_assert' > 487 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > | ^~~~~~~~~~~~~~~~~~~ > include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > | ^~~~~~~~~~~~~~~~~~ > include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG' > 59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") > | ^~~~~~~~~~~~~~~~ > arch/arm64/include/asm/io.h:193:17: note: in expansion of macro 'BUILD_BUG' > 193 | BUILD_BUG(); > | ^~~~~~~~~ > > Add a check to ensure that the argument is in fact a constant before > calling into __const_memcpy_toio_aligned32(). > > Fixes: ead79118dae6 ("arm64/io: Provide a WC friendly __iowriteXX_copy()") > Signed-off-by: Arnd Bergmann > --- > arch/arm64/include/asm/io.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h > index 4ff0ae3f6d66..44913f227060 100644 > --- a/arch/arm64/include/asm/io.h > +++ b/arch/arm64/include/asm/io.h > @@ -199,7 +199,8 @@ void __iowrite32_copy_full(void __iomem *to, const void *from, size_t count); > static inline void __const_iowrite32_copy(void __iomem *to, const void *from, > size_t count) > { > - if (count == 8 || count == 4 || count == 2 || count == 1) { > + if (__builtin_constant_p(count) && > + (count == 8 || count == 4 || count == 2 || count == 1)) { > __const_memcpy_toio_aligned32(to, from, count); > dgh(); > } else { I don't think this is the right fix. The idea was that this was checked in __iowrite32_copy(), which does: #define __iowrite32_copy(to, from, count) \ (__builtin_constant_p(count) ? \ __const_iowrite32_copy(to, from, count) : \ __iowrite32_copy_full(to, from, count)) ... and so __const_iowrite32_copy() should really be marked as __always_inline, and the same for __const_memcpy_toio_aligned32(), to guarantee that both get inlined and such that __const_memcpy_toio_aligned32() sees a constant. The same reasoning applies to __const_iowrite64_copy() and __const_memcpy_toio_aligned64(). Checking for a constant in __const_iowrite32_copy() doesn't guarantee that __const_memcpy_toio_aligned32() is inlined and will actually see a constant. Does diff the below you for you? Mark. ---->8---- diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h index 4ff0ae3f6d669..f4350aae92d5d 100644 --- a/arch/arm64/include/asm/io.h +++ b/arch/arm64/include/asm/io.h @@ -153,8 +153,9 @@ extern void __memset_io(volatile void __iomem *, int, size_t); * emit the large TLP from the CPU. */ -static inline void __const_memcpy_toio_aligned32(volatile u32 __iomem *to, - const u32 *from, size_t count) +static __always_inline void +__const_memcpy_toio_aligned32(volatile u32 __iomem *to, const u32 *from, + size_t count) { switch (count) { case 8: @@ -196,8 +197,8 @@ static inline void __const_memcpy_toio_aligned32(volatile u32 __iomem *to, void __iowrite32_copy_full(void __iomem *to, const void *from, size_t count); -static inline void __const_iowrite32_copy(void __iomem *to, const void *from, - size_t count) +static __always_inline void +__const_iowrite32_copy(void __iomem *to, const void *from, size_t count) { if (count == 8 || count == 4 || count == 2 || count == 1) { __const_memcpy_toio_aligned32(to, from, count); @@ -212,8 +213,9 @@ static inline void __const_iowrite32_copy(void __iomem *to, const void *from, __const_iowrite32_copy(to, from, count) : \ __iowrite32_copy_full(to, from, count)) -static inline void __const_memcpy_toio_aligned64(volatile u64 __iomem *to, - const u64 *from, size_t count) +static __always_inline void +__const_memcpy_toio_aligned64(volatile u64 __iomem *to, const u64 *from, + size_t count) { switch (count) { case 8: @@ -255,8 +257,8 @@ static inline void __const_memcpy_toio_aligned64(volatile u64 __iomem *to, void __iowrite64_copy_full(void __iomem *to, const void *from, size_t count); -static inline void __const_iowrite64_copy(void __iomem *to, const void *from, - size_t count) +static __always_inline void +__const_iowrite64_copy(void __iomem *to, const void *from, size_t count) { if (count == 8 || count == 4 || count == 2 || count == 1) { __const_memcpy_toio_aligned64(to, from, count);