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 35D1D423783 for ; Thu, 30 Jul 2026 12:04:41 +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=1785413083; cv=none; b=Et8L7MMmMt70OCThGjE3cfRMi2RJDMeg+cjeKKQrImhs4V4m0hPypFDW5qIHLXQmyJ5b4lg7OhPcD7bLMwOs6P+nEEOJuzugYRTNjik7z6jMWBuXwkvmWNOqhSqJj7wIPobzBI5wvFbbOGt7fzMP1RpVnbcbXRaPSp/Jhqc8G0I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785413083; c=relaxed/simple; bh=94KvrpdqZCT41H1B9dUsZ2ZIG0PQ1N/78xwtbnNt9wI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XV6fNC8RlvHc66/0/xdEheMbQMIj5YMgVDNAr5d75JIbAEVluxb8rZDyoonj/0Ld6EsFZCGSsLND8CRxIXkswQ8jUfT7kdBJuWaFK3OC3Pdg8EJzTp3OqOiCbmEf644XRp3tDCQvK68sbwNdMroh/hnQ/Yp265WcIhtuIggCHk0= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=iMBGTocu; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="iMBGTocu" 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 6FA501684; Thu, 30 Jul 2026 05:04:36 -0700 (PDT) Received: from [10.1.34.163] (e121487-lin.cambridge.arm.com [10.1.34.163]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2D45B3F86F; Thu, 30 Jul 2026 05:04:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785413080; bh=94KvrpdqZCT41H1B9dUsZ2ZIG0PQ1N/78xwtbnNt9wI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iMBGTocuJfn1iRKh3+xhufyOqq972tGhZvvKqJahwEe1iyFk7E4Jcnk9BB1ler2lW FtJINy0uhHl2GNoIYbmEVuLrEVxYfIsL5WERGO593bQ+sAtgPdiMPzbOyF83IXhSId qFuFdSZcqnnR7cixqtQxz3Z4vvGsbqaikdchNigo= Message-ID: <53120347-2926-4d02-9e90-2c0c489b33bd@arm.com> Date: Thu, 30 Jul 2026 13:04:36 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 06/13] arm64: percpu: Add infrastructure for preemptible this_cpu_*() ops To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, ada.coupriediaz@arm.com, ardb@kernel.org, catalin.marinas@arm.com, hca@linux.ibm.com, linux-kernel@vger.kernel.org, maz@kernel.org, peterz@infradead.org, ruanjinjie@huawei.com, will@kernel.org, yang@os.amperecomputing.com References: <20260728123859.2911495-1-mark.rutland@arm.com> <20260728123859.2911495-7-mark.rutland@arm.com> Content-Language: en-GB From: Vladimir Murzin In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/30/26 11:59, Mark Rutland wrote: > On Wed, Jul 29, 2026 at 03:25:52PM +0100, Vladimir Murzin wrote: >> On 7/28/26 13:38, Mark Rutland wrote: >>> +#define __VAL_PCPU_GPRS(pcp, off, addr) \ >>> + "(" \ >>> + "(.L__gpr_num_" pcp " << 0) | " \ >>> + "(.L__gpr_num_" off " << 5) | " \ >>> + "(.L__gpr_num_" addr " << 10)" \ >>> + ")" >> Later in the patch, there is a comment stating that these registers >> are not expected to overlap. I can also see that early-clobber >> constraints are applied to the output registers later in the patch >> series, so the code is correct. >> >> However, would it be possible to add assertions that detect register >> overlap, perhaps something like: >> >> ".if (.L__gpr_num_" pcp "== .L__gpr_num_" off ") ||" \ >> " (.L__gpr_num_" pcp "== .L__gpr_num_" addr ") ||" \ >> " (.L__gpr_num_" off "== .L__gpr_num_" addr")" \ >> ".error "inline asm registers overlap" \ >> ".endif" \ > That's a good idea. I've added the following: > > | #define __ASSERT_PCPU_GPRS_UNIQUE(pcp, off, addr) \ > | ".if (" \ > | "(.L__gpr_num_" pcp " == .L__gpr_num_" off ") || " \ > | "(.L__gpr_num_" pcp " == .L__gpr_num_" addr ") || " \ > | "(.L__gpr_num_" off " == .L__gpr_num_" addr")" \ > | " )\n" \ > | ".error \"PCPU GPRS overlap: {" pcp "," off "," addr "}\"\n" \ > | ".endif\n" > | > | #define ____PCPU_GPRS_BEGIN(gprs, pcp, off, addr) \ > | __DEFINE_ASM_GPR_NUMS \ > | __DEFINE_ASM_GPR_ALIASES \ > | __ASSERT_PCPU_GPRS_UNIQUE(pcp, off, addr) \ > | " mov w" off ", #" __VAL_PCPU_GPRS(pcp, off, addr) "\n" \ > | " strh w" off ", " gprs "\n" \ > | __KERN_ASM_CPU_OFFSET(off) "\n" > > With that, we have enough ".L__gpr_num_" string concatenation that we > should probably have: > > | #define __GPR_NUM(r) "(.L__gpr_num_" r ")" > > ... so I'll go add a preparatory patches adding that and cleaning up > existing usage. > > Mark. > Awesome! Cheers Vladimir