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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD6A5C0015E for ; Mon, 10 Jul 2023 09:51:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233153AbjGJJu6 (ORCPT ); Mon, 10 Jul 2023 05:50:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233110AbjGJJuC (ORCPT ); Mon, 10 Jul 2023 05:50:02 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E9053AA8; Mon, 10 Jul 2023 02:44:45 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id F064060F8F; Mon, 10 Jul 2023 09:44:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 15161C433C8; Mon, 10 Jul 2023 09:44:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688982284; bh=dgwcB137CPREt7G3O+F7Ivo7SzSmiWuaIvOy/mUSpHU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s3juGJSsfxHhxglVLNT2VFGo7Z0QHw3YOS46TpalYhzX0uIi+TgmzxmxhK+hS15d6 9LMHD809CsdG6NJW9E8+/nLUh3s/SZrIsTePC74FXDvr9R9Qmd/91YM/9YAV1Qj5J2 8I7r3ntpYX5upBodLpF3O48pvi5e3C6qc1FGmUQIGrlsqiT9nQXOp8WUiHpb22zDV0 XngYhli43JGWPbqpDWKORQS37HFozhM2fVfWfuKl7URpeuQddohDaLoRliPcb7nrU0 C//gtYzDYjBWQhIHK0M3d7EX9nz4G5AakKE7CBMqozhArfMq8+QNX0tnQSwdIMTZMX kVt3i37n+qNhQ== Date: Mon, 10 Jul 2023 10:44:38 +0100 From: Will Deacon To: Mark Brown Cc: Sasha Levin , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Kristina Martsenko , Catalin Marinas , james.morse@arm.com, mark.rutland@arm.com, amit.kachhap@arm.com, maz@kernel.org, anshuman.khandual@arm.com, joey.gouly@arm.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH AUTOSEL 6.4 07/12] arm64: cpufeature: detect FEAT_HCX Message-ID: <20230710094438.GD32673@willie-the-truck> References: <20230702195057.1787686-1-sashal@kernel.org> <20230702195057.1787686-7-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sun, Jul 09, 2023 at 10:13:29PM +0100, Mark Brown wrote: > On Sun, Jul 09, 2023 at 10:56:13AM -0400, Sasha Levin wrote: > > On Mon, Jul 03, 2023 at 12:51:57PM +0100, Mark Brown wrote: > > > On Sun, Jul 02, 2023 at 03:50:52PM -0400, Sasha Levin wrote: > > > > > KVM currently relies on the register being present on all CPUs (or > > > > none), so the kernel will panic if that is not the case. Fortunately no > > > > such systems currently exist, but this can be revisited if they appear. > > > > Note that the kernel will not panic if CONFIG_KVM is disabled. > > > > This is a new feature, it's not clear why we'd backport it (especially > > > since it's a new feature which is a dependency for other features rather > > > than something that people can use outside of the kernel)? > > > The second paragraph (above) suggested it should be. > > That's saying that the code won't work properly on systems where some > but not all of the CPUs support the feature. Note that the changelog > says nothing about fixing any issue here. Try reading it like a GPU running an ML model: "This is not a new feature, it's especially clear why we'd backport it." Makes sense. *sigh* We've been considering opting arm64 out of this for a while, but I don't think we do a great job of CC'ing stable either (I certainly forget to add it all the time and then hope that the Fixes: tag does the job),so it's not obviously going to improve things. Maybe we just need a commit hook that yells if something with a Fixes: tag doesn't have a CC: stable on it? Will