From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33785) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gSDBf-0002Ln-G5 for qemu-devel@nongnu.org; Wed, 28 Nov 2018 22:40:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gSDBc-0002Jv-8N for qemu-devel@nongnu.org; Wed, 28 Nov 2018 22:40:23 -0500 Message-ID: <39eb027df3340121ba9877e689e4d0a2747c5e43.camel@kernel.crashing.org> From: Benjamin Herrenschmidt Date: Thu, 29 Nov 2018 14:39:55 +1100 In-Reply-To: <20181129004718.GJ2251@umbus.fritz.box> References: <20181116105729.23240-1-clg@kaod.org> <20181116105729.23240-9-clg@kaod.org> <20181127234956.GR2251@umbus.fritz.box> <20181129004718.GJ2251@umbus.fritz.box> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v5 08/36] ppc/xive: introduce a simplified XIVE presenter List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson , =?ISO-8859-1?Q?C=E9dric?= Le Goater Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org On Thu, 2018-11-29 at 11:47 +1100, David Gibson wrote: > > 1) read/write accessors which take a word number > > 2) A "get" accessor which copies the whole structure, but "write" > accessor which takes a word number. The asymmetry is a bit ugly, but > it's the non-atomic writeback of the whole structure which I'm most > uncomfortable with. It shouldn't be a big deal though, there are HW facilities to access the structures "atomically" anyway, due to the caching done by the XIVE. > 3) A map/unmap interface which gives you / releases a pointer to the > "live" structure. For powernv that would become > address_space_map()/unmap(). For PAPR it would just be reutn pointer > / no-op.