From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1ZtbfM-00079W-EV for mharc-qemu-trivial@gnu.org; Tue, 03 Nov 2015 08:30:24 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34079) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtbfF-00072N-9o for qemu-trivial@nongnu.org; Tue, 03 Nov 2015 08:30:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZtbfB-0002AV-99 for qemu-trivial@nongnu.org; Tue, 03 Nov 2015 08:30:17 -0500 Received: from s16892447.onlinehome-server.info ([82.165.15.123]:35113) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtbfB-000279-2S; Tue, 03 Nov 2015 08:30:13 -0500 Received: from host31-50-136-216.range31-50.btcentralplus.com ([31.50.136.216] helo=[192.168.1.65]) by s16892447.onlinehome-server.info with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1Ztbev-0003l4-3T; Tue, 03 Nov 2015 13:30:00 +0000 Message-ID: <5638B6BC.50000@ilande.co.uk> Date: Tue, 03 Nov 2015 13:29:32 +0000 From: Mark Cave-Ayland User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 To: Michael Tokarev , Julio Guerra , qemu-devel@nongnu.org, qemu-ppc@nongnu.org, qemu-trivial@nongnu.org References: <1444844599-33161-1-git-send-email-julio@farjump.io> <5638A5AF.9000709@msgid.tls.msk.ru> In-Reply-To: <5638A5AF.9000709@msgid.tls.msk.ru> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 31.50.136.216 X-SA-Exim-Mail-From: mark.cave-ayland@ilande.co.uk X-SA-Exim-Version: 4.2.1 (built Sun, 08 Jan 2012 02:45:44 +0000) X-SA-Exim-Scanned: No (on s16892447.onlinehome-server.info); Unknown failure X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 82.165.15.123 Cc: christophe@farjump.io, Alexander Graf Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH v2] taget-ppc: Fix read access to IBAT registers higher than IBAT3 X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 03 Nov 2015 13:30:22 -0000 On 03/11/15 12:16, Michael Tokarev wrote: > 03.11.2015 11:00, Julio Guerra wrote: >> Ping :) > > Well, I'm not sure what can I do with this. I've no idea what is IBAT to start > with, so while technically the patch is a one-liner, I've no idea what it does > and how trivial it is :) > > Maybe you can include some context which teaches me what it is all about, and in > that case it becomes really trivial, or.. I dunno :) FWIW PPC has a set of IBAT and DBAT registers on chip, each of which indicates a large continuous physical/virtual memory mapping for Instruction and Data memory respectively. The idea is that the OS can use these to provide "fast" virtual to physical lookups instead of invoking a time-consuming hash lookup to provide the translation. >From casual observation comparing with spr_write_ibatu_h() in the same file (which already includes the +4 offset that the patch is adding to spr_read_ibat_h()), it does look like a genuine bug. However it really needs someone who understands PPC architecture a bit more to give a RB to ensure this is doing the right thing. ATB, Mark. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34185) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZtbfQ-0007F5-E4 for qemu-devel@nongnu.org; Tue, 03 Nov 2015 08:30:32 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZtbfP-0002El-Gz for qemu-devel@nongnu.org; Tue, 03 Nov 2015 08:30:28 -0500 Message-ID: <5638B6BC.50000@ilande.co.uk> Date: Tue, 03 Nov 2015 13:29:32 +0000 From: Mark Cave-Ayland MIME-Version: 1.0 References: <1444844599-33161-1-git-send-email-julio@farjump.io> <5638A5AF.9000709@msgid.tls.msk.ru> In-Reply-To: <5638A5AF.9000709@msgid.tls.msk.ru> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] taget-ppc: Fix read access to IBAT registers higher than IBAT3 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Michael Tokarev , Julio Guerra , qemu-devel@nongnu.org, qemu-ppc@nongnu.org, qemu-trivial@nongnu.org Cc: christophe@farjump.io, Alexander Graf On 03/11/15 12:16, Michael Tokarev wrote: > 03.11.2015 11:00, Julio Guerra wrote: >> Ping :) > > Well, I'm not sure what can I do with this. I've no idea what is IBAT to start > with, so while technically the patch is a one-liner, I've no idea what it does > and how trivial it is :) > > Maybe you can include some context which teaches me what it is all about, and in > that case it becomes really trivial, or.. I dunno :) FWIW PPC has a set of IBAT and DBAT registers on chip, each of which indicates a large continuous physical/virtual memory mapping for Instruction and Data memory respectively. The idea is that the OS can use these to provide "fast" virtual to physical lookups instead of invoking a time-consuming hash lookup to provide the translation. >>From casual observation comparing with spr_write_ibatu_h() in the same file (which already includes the +4 offset that the patch is adding to spr_read_ibat_h()), it does look like a genuine bug. However it really needs someone who understands PPC architecture a bit more to give a RB to ensure this is doing the right thing. ATB, Mark.