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.