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 05F26156661 for ; Thu, 20 Nov 2025 17:30:50 +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=1763659854; cv=none; b=DgDJE+aLcPpquiUOFQoiBM3mTYnRsCqf/36lP8evN+CSGIFEdUrB9j/rJPDTiaTXk7Z+Mu3OPnYq+ypEBD85Ga+mcSAgn91WT/018n5Su3DCHVbn1717IgP24UXKHt0JoIO+g2hBj08o0pwKt8l2fkQ8wfDVuzUczhYggUi1RXU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763659854; c=relaxed/simple; bh=S/mYcHUBgQSXlPZQTiJvzhkSTaW0X3B+RJXDl7zvEUw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=P4Bt6vYm5ziREbRUh78BIZre0y7nbq8/t4iQRAkk9xLNFRBhvvNzTs10v0n1b0DsGywgz+8ezhdBKxbstgNpg/euXMxBK0gqO7o2I4ByAdfIItDwCcmFE3iALDhzJjBWp7cYnRLQsbByAATB+c/y4EpwV/5fZ23g7dmEFMUl+Ek= 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 98A9F339; Thu, 20 Nov 2025 09:30:42 -0800 (PST) Received: from arm.com (arrakis.cambridge.arm.com [10.1.197.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E8A1F3F66E; Thu, 20 Nov 2025 09:30:48 -0800 (PST) Date: Thu, 20 Nov 2025 17:30:46 +0000 From: Catalin Marinas To: Conor Dooley Cc: linux-arm-kernel@lists.infradead.org, Conor Dooley , Randy Dunlap , Jonathan Cameron , Will Deacon , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] arm64, lib: make ARM64 select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION not GENERIC_CPU_CACHE_MAINTENANCE Message-ID: References: <20251119-zippy-distinct-1e2a7da7b69b@spud> 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: <20251119-zippy-distinct-1e2a7da7b69b@spud> On Wed, Nov 19, 2025 at 07:08:27PM +0000, Conor Dooley wrote: > From: Conor Dooley > > Randy pointed out that the newly added GENERIC_CPU_CACHE_MAINTENANCE > was unusual, in that it selected an ARCH_HAS_... option, unlikely > anything else in lib/Kconfig. Switch things around, so that arm64 > selects ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION and then > GENERIC_CPU_CACHE_MAINENANCE will in turn be automatically enabled. > > Suggested-by: Randy Dunlap > Acked-by: Jonathan Cameron > Signed-off-by: Conor Dooley > --- > Catalin, you voiced a take on this already apparently that lead to the > current implementation so I'd like an ack from you or Will here. > My comment on the original thread, in response to Randy saying it was > backwards, that accompanied the diff was: > Maybe it is backwards, but I feel like this way is more logical. ARM64 > has memregion invalidation only because this generic approach is > enabled, so the arch selects what it needs to get the support. > Alternatively, something like (diff was here) implies (to me at least) > that arm64 has memregion invalidation as an architectural feature and > that the GENERIC_CPU_CACHE_MAINTENANCE option is a just common > cross-arch code, like generic entry etc, rather than being the option > gating the drivers that provide the feature in the first place. > Ultimately, the .config produced is the same either way, just depends on > what impression you want to give in the arch Kconfig, which might not > really be a big deal, just semantics. Either way, I'd like an ack :) I really don't remember what I said before ;). As you describe above, there are two somewhat complementary options - ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION where an arch port can provide this API and GENERIC_CPU_CACHE_MAINTENANCE as a generic way of providing the same API. arm64 does the latter. > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 5f7f63d24931..75b2507f7eb2 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -21,6 +21,7 @@ config ARM64 > select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE > select ARCH_HAS_CACHE_LINE_SIZE > select ARCH_HAS_CC_PLATFORM > + select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION > select ARCH_HAS_CURRENT_STACK_POINTER > select ARCH_HAS_DEBUG_VIRTUAL > select ARCH_HAS_DEBUG_VM_PGTABLE > @@ -146,7 +147,6 @@ config ARM64 > select GENERIC_ARCH_TOPOLOGY > select GENERIC_CLOCKEVENTS_BROADCAST > select GENERIC_CPU_AUTOPROBE > - select GENERIC_CPU_CACHE_MAINTENANCE > select GENERIC_CPU_DEVICES > select GENERIC_CPU_VULNERABILITIES > select GENERIC_EARLY_IOREMAP > diff --git a/lib/Kconfig b/lib/Kconfig > index 09aec4a1e13f..ac223e627bc5 100644 > --- a/lib/Kconfig > +++ b/lib/Kconfig > @@ -544,8 +544,9 @@ config ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION > bool > > config GENERIC_CPU_CACHE_MAINTENANCE > - bool > - select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION > + def_bool y > + depends on ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION > + depends on ARM64 That's what we do if GENERIC_CPU_CACHE_MAINTENANCE depends on some arch code but that's not the case here. GENERIC_CPU_CACHE_MAINTENANCE is an alternative implementation that an arch can select if it does not provide its own. I find the current code without the above patch better. Maybe what gets confusing here is that the core code uses ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION directly. A more involved fix would be something like: config CPU_CACHE_INVALIDATE_MEMREGION def_bool y depends on ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION || GENERIC_CPU_CACHE_MAINTENANCE and then go and change all the uses of ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION. Up to you, the current code also works for me. -- Catalin