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 B99ABC004D4 for ; Thu, 19 Jan 2023 22:31:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229770AbjASWbN (ORCPT ); Thu, 19 Jan 2023 17:31:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230265AbjASW3l (ORCPT ); Thu, 19 Jan 2023 17:29:41 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B24A8A731E; Thu, 19 Jan 2023 14:13:46 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D9AB061D98; Thu, 19 Jan 2023 22:13:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F1A94C433D2; Thu, 19 Jan 2023 22:13:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1674166425; bh=0TfIfsT7UPQtXb3sT22jU7uGw99A7souxhvdf2e+V9c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UXJOQ07ln3xNI1VGM2Ekd+dqU7VasYlqn85+drkmHpU8ZmhSLftCzVTUNeMqDjOyu dsh6nk7CJ4/CyDlbu+r5pov2snB5LFE3j9fETGo7u68xTcvbNFpRJz3JckN/MjJ3Hn Ux/h6yeaTTRxic34et2/mHCxnKDYXBfeCKgdeJm+2ribsgpFeNq/zFNTilDFpPkybn kfzNcDxR8G2apTwQk103syCxkrc72QR2KJyEP++x5QPxtpABIV2/EG+wwiz5WBkbZI kk3XvZccPbyeAVdd6BnD3ScThEr8xdC9P5p67lZ55ngcDVceqFIG5HXWb3S4JB6MB5 3S5f4GHdgiakA== Date: Thu, 19 Jan 2023 22:13:39 +0000 From: Conor Dooley To: Andrew Jones , Heiko =?iso-8859-1?Q?St=FCbner?= , Palmer Dabbelt , kernel@esmil.dk, bjorn@kernel.org Cc: Heiko =?iso-8859-1?Q?St=FCbner?= , Palmer Dabbelt , Paul Walmsley , Albert Ou , Anup Patel , Atish Patra , Jisheng Zhang , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, David Abdurachmanov Subject: Re: [PATCH v3 05/13] riscv: cpufeature: extend riscv_cpufeature_patch_func to all ISA extensions Message-ID: References: <20230111171027.2392-1-jszhang@kernel.org> <20230111171027.2392-6-jszhang@kernel.org> <2398293.3Lj2Plt8kZ@diego> <20230112092136.f2g43hrhmrqouy4y@orel> <20230119082903.yk3uslfrjtxzassi@orel> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="t/O9pox46sePZAp3" Content-Disposition: inline In-Reply-To: <20230119082903.yk3uslfrjtxzassi@orel> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --t/O9pox46sePZAp3 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Me again! On Thu, Jan 19, 2023 at 09:29:03AM +0100, Andrew Jones wrote: > On Wed, Jan 18, 2023 at 09:54:46PM +0000, Conor Dooley wrote: > > Hey! > >=20 > > I guess here is the right place to follow up on all of this stuff... > >=20 > > On Sat, Jan 14, 2023 at 08:32:37PM +0000, Conor Dooley wrote: > > Today at [1] we talked a bit about the various bits going on here. > > I'll attempt to summarise what I remember, but I meant to do this > > several hours ago and am likely to make a hames of it. > >=20 > > For Zbb/unaligned stuff, the sentiment was along the lines of there > > needing to be a performance benefit to justify the inclusion. > > Some of us have HW that is (allegedly) capable of Zbb, and, if that's t= he I did some very very basic testing today. Ethernet is still a no-go on my visionfive 2 board, but the sd card works at least, so I can run w/ Zbb code people want & we can see how it goes! At the very least, it is capable of executing the instructions that were used in Appendix A. I didn't try to do anything else, because I am lazy and if there were some pre-existing test programs I didn't want to go and write out a bunch of asm myself! impid appears to be 0x4210427, if that means anything to anyone! > > case, will give it a go. > > I think it was similar for unaligned, since there is nothing yet that > > supports this behaviour, we should wait until a benefit is demonstrable. > >=20 > > On the subject of grouping extension/non-extension capabilities into a > > single cpufeature, Palmer mentioned that GCC does something similar, > > for the likes of the Ventana vendor extensions, that are unlikely to be > > present in isolation. Jess pointed out on IRC that GCC doesn't support XVentanaCondOps so maybe there was a mixup there. I don't think that really matters though, as the point stands regardless of whether it was in GCC or not. > > Those are (or were?) probed as a group of extensions rather than > > individually. > > I think it was said it'd make sense for us to unify extensions that will > > only ever appear together single psuedo cpufeature too. > >=20 > > For the bitfield approach versus creating pseudo cpufeatures discussion > > & how to deal with that in alternatives etc, I'm a bit less sure what t= he > > outcome was. > > IIRC, nothing concrete was said about either approach, but maybe it was > > implied that we should do as GCC does, only grouping things that won't > > ever been seen apart. > > Figuring that out seems to have been punted down the road, as the > > inclusion of our only current example of this (Zbb + unaligned) is > > dependant on hardware showing up that actually benefits from it. > >=20 > > The plan then seemed to be press ahead with this series & test the > > benefits of the Zbb str* functions in Zbb capable hardware before making > > a decision there. > >=20 > > Hopefully I wasn't too far off with that summary... >=20 > This matches my recollection. Thanks for the summary, Conor. Cool, thanks. --t/O9pox46sePZAp3 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCY8nAkwAKCRB4tDGHoIJi 0jpZAP976+x+ZkRVzdavgP77bKd1eLS8QZmSr/7+1xVouP4CvgEAtgyo6s7+n/qA oANTfCfXncWnh8YtZaGwZlbAOakaKgc= =C0SZ -----END PGP SIGNATURE----- --t/O9pox46sePZAp3--