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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 15F94C6FA83 for ; Mon, 12 Sep 2022 18:11:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=3jPxJlTC8I1NyiCWv9oukL4G5RbbtWU6jDHiX2z26CU=; b=G7n2CX5OQGHh3Q 495qwq3PtNezUuVUAx7dhTDFsv6w7gwS3VMOmYfVwg2RX+Vi6AEGC5KNoEBdw+QBnj9NeIPYo0B/K hvB428RLt1cuZ0VOOBESmvmqcclez9EZeNqCBvMbLoOhvVxSs5FuVJI0CVjEyH4XObbawgVCJc9Tg fZEKy8xtODoCd9tCj4lL7kH+igCUuOR+iNInqbwPPpYsTpbOs6oEYifs66JjV7WK0attsU+uuxsyB YlnTkm9F1moCiZiUhqNEpUaj8tEw7NKnlyL5U5Zuc/K8rBVGa00Yfhz8IdgcjaRchNfTxnxxNvjfQ ttahzjfoZd/9WPkoeGkQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oXnt6-00CKvu-R2; Mon, 12 Sep 2022 18:10:29 +0000 Received: from mail-pl1-x632.google.com ([2607:f8b0:4864:20::632]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oXnsB-00CJzW-Qh for linux-arm-kernel@lists.infradead.org; Mon, 12 Sep 2022 18:09:33 +0000 Received: by mail-pl1-x632.google.com with SMTP id v1so9336649plo.9 for ; Mon, 12 Sep 2022 11:09:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=krOgoVxwfTTiN1DsCbbELdSz8T1/ug820utrPBGbV+I=; b=bbbi3kXh+LuJ615H9/uybCphjVG9PAN1wwm41NzOSOv+PgbEvdPHXSa/FUVuNSX9rF cB35qq0zyXJFhMRWzip77xbxMugOe/lnqgHG02o/U6PABq7jAyVJo8WkRqikgUWx82gh dhVsA+MMAdP09T3YjlDMYRAX0+zXzJxFXC8SHN333GxgUBHMYHd8srOQMgcxkNZJ71yK +V8aM7TWpFRJyvy10jiXA+/A+60P1VY43ycrGU0XA7FXO3AwTGT3D5d6h2XOCj0Nlmlz i6LFPmnRpVRHzrV/hIcNEO22P7kfgXapvN5dcK3PfRFuBYu1kFtrpqBVfUUvYBhcd9xW lYMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=krOgoVxwfTTiN1DsCbbELdSz8T1/ug820utrPBGbV+I=; b=HsUPOsIQUOD91lCOd6dKg/NWDzWrz9xIeZBK96rhgumSBfKwc/DeHqtxxVg6aqS0EV E/h2OikgWYgYVMxg/AJAq8ahDCeyxlGLAWjfJYh7KEwuawKYlRmt04SvbzgkqkUx4FCo dOh0oNM/YkM6Jsd8f2wC5OPjuD5jiZZY9605I5F0F6gInGL9d0Lg7lJMu9f3t2NindfD xkGMpOYsVRjyjUSWELLUzRvChomm2lYwe+10xyQ7SUocEwZGL628SWhprwvbUPr7CK1s 0iAHPGa0Ajqk+fJSeUKYoifyFSi1FC8ZPBgncQVtzl00ykaBt3VxtnaO45AR54xwAvdD Pihw== X-Gm-Message-State: ACgBeo1z0xhgQyh3QA8jRZGWqHRyKlXnVqAPyXV/dzB4f7QXufBRi5Nx ae+jiFVrX2vkTZ4YSaHt/QV08Farxm0yHgcUP22yoekWhk74mg== X-Google-Smtp-Source: AA6agR4X+Fq14UwFKI68855EfSw8R3jyZUluAJHbDZ9hWSkXwABmcDTlgOOQ8IOazviEmBzF0o8L3K5Y3Kb2rhBqyxM= X-Received: by 2002:a17:90b:1c81:b0:1fb:887c:f82e with SMTP id oo1-20020a17090b1c8100b001fb887cf82emr25159974pjb.92.1663006169735; Mon, 12 Sep 2022 11:09:29 -0700 (PDT) MIME-Version: 1.0 References: <20220901141307.2361752-1-georgepee@gmail.com> In-Reply-To: From: George Pee Date: Mon, 12 Sep 2022 13:09:17 -0500 Message-ID: Subject: Re: [PATCH] Report support for optional ARMv8.2 half-precision floating point extension To: "Russell King (Oracle)" Cc: Catalin Marinas , Robin Murphy , "Kirill A. Shutemov" , Austin Kim , Ard Biesheuvel , Mike Rapoport , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220912_110931_921033_80613087 X-CRM114-Status: GOOD ( 25.20 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 12, 2022 at 8:05 AM Russell King (Oracle) wrote: > > On Fri, Sep 09, 2022 at 04:05:53PM +0100, Catalin Marinas wrote: > > On Fri, Sep 09, 2022 at 09:57:39AM -0500, George Pee wrote: > > > The details are here. I originally thought it was a compiler bug > > > because it first showed up after a toolchain update. > > > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106763 > > > > > > Since FP16 is an optional extension, wouldn't it be beneficial to a > > > user who compiled some userspace float16 code using gcc > > > -mcpu=cortex-a55 which ran on a cortex-a55 with FP16 extensions but > > > SIGILL'd on a cortex-a55 w/o FP16? > > > > (please don't top-post) > > > > My point is that if the kernel doesn't have full support for FP16, it > > shouldn't advertise it to user even if the hardware supports it. If you > > fix the kernel to properly handle FP16 on supporting hardware, then the > > HWCAP part is fine by me. > > Presumably, the only CPUs that are going to support FP16 will have > non-trapping floating point, so the support code shouldn't be entered > at any time to emulate a half-precision instruction, but only to > handle the lazy restore of the thread's floating point registers? > > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last! I didn't see this until after I submitted v2 of the patch. Let me take a look at the fp emulation code path. I had assumed that CP9 handling would work just like CP10/CP11 does in entry-armv.S and wouldn't need any special handling. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel