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 X-Spam-Level: X-Spam-Status: No, score=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11804C433B4 for ; Mon, 3 May 2021 05:21:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CC26B611AD for ; Mon, 3 May 2021 05:21:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229933AbhECFTI (ORCPT ); Mon, 3 May 2021 01:19:08 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:29905 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229462AbhECFTH (ORCPT ); Mon, 3 May 2021 01:19:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620019093; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AuEiYD42Zz5WBftkQsHhyYFKqxjbzt+m6olruO+nNkM=; b=ZigBA+x8GBqXIOWx3UCjUHmKq+pBBkgmHWnDtzBPwzh46gcrBrdzjPdK7Mub47jTjEKciZ eXj1Ni1/p2kxA+phdERV730RAEdXPHQLJlVLfA8S4iZabZrWGO2yQr3ZvKtqi5Zz4sAF5V IZmPLYjEpfMmABMeALFH0Nok97qmZWI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-285-Ti7evn4XNcGDopxRMF8L-g-1; Mon, 03 May 2021 01:18:11 -0400 X-MC-Unique: Ti7evn4XNcGDopxRMF8L-g-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1A2A350203; Mon, 3 May 2021 05:18:09 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-112-137.ams2.redhat.com [10.36.112.137]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CAA3B781E0; Mon, 3 May 2021 05:18:04 +0000 (UTC) From: Florian Weimer To: Len Brown Cc: Borislav Petkov , Willy Tarreau , Andy Lutomirski , "Bae, Chang Seok" , Dave Hansen , X86 ML , LKML , linux-abi@vger.kernel.org, "libc-alpha@sourceware.org" , Rich Felker , Kyle Huey , Keno Fischer Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related features References: <20210415044258.GA6318@zn.tnic> <20210415052938.GA2325@1wt.eu> <20210415054713.GB6318@zn.tnic> <20210419141454.GE9093@zn.tnic> <20210419191539.GH9093@zn.tnic> <20210419215809.GJ9093@zn.tnic> Date: Mon, 03 May 2021 07:18:16 +0200 In-Reply-To: (Len Brown's message of "Sun, 2 May 2021 11:27:26 -0400") Message-ID: <87bl9s8kfb.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Len Brown: > 5. If the feature is enabled in XCR0, the user happily uses it. > > For AMX, Linux implements "transparent first use" > so that it doesn't have to allocate 8KB context switch > buffers for tasks that don't actually use AMX. > It does this by arming XFD for all tasks, and taking a #NM > to allocate a context switch buffer only for those tasks > that actually execute AMX instructions. What happens if the kernel cannot allocate that additional context switch buffer? Thanks, Florian