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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 AF21DC433E0 for ; Wed, 3 Jun 2020 15:44:24 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8282C20679 for ; Wed, 3 Jun 2020 15:44:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8282C20679 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=eik.bme.hu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:34722 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jgVZ1-0002Fi-Of for qemu-devel@archiver.kernel.org; Wed, 03 Jun 2020 11:44:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41892) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jgVYV-0001pd-M3 for qemu-devel@nongnu.org; Wed, 03 Jun 2020 11:43:51 -0400 Received: from zero.eik.bme.hu ([152.66.115.2]:51061) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jgVYS-0004h6-De for qemu-devel@nongnu.org; Wed, 03 Jun 2020 11:43:50 -0400 Received: from zero.eik.bme.hu (blah.eik.bme.hu [152.66.115.182]) by localhost (Postfix) with SMTP id 48685746335; Wed, 3 Jun 2020 17:43:45 +0200 (CEST) Received: by zero.eik.bme.hu (Postfix, from userid 432) id 2623274632C; Wed, 3 Jun 2020 17:43:45 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by zero.eik.bme.hu (Postfix) with ESMTP id 2495D74594E; Wed, 3 Jun 2020 17:43:45 +0200 (CEST) Date: Wed, 3 Jun 2020 17:43:45 +0200 (CEST) From: BALATON Zoltan To: P J P Subject: Re: [PATCH] ati-vga: increment mm_index in ati_mm_read/write In-Reply-To: Message-ID: References: <20200603124732.1137892-1-ppandit@redhat.com> <20200603134404.xdb2koul7fatv4ez@sirius.home.kraxel.org> User-Agent: Alpine 2.22 (BSF 395 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Received-SPF: pass client-ip=152.66.115.2; envelope-from=balaton@eik.bme.hu; helo=zero.eik.bme.hu X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/03 09:56:49 X-ACL-Warn: Detected OS = FreeBSD 9.x or newer [fuzzy] X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Ren Ding , Yi Ren , Gerd Hoffmann , Hanqing Zhao , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 3 Jun 2020, BALATON Zoltan wrote: > On Wed, 3 Jun 2020, P J P wrote: >> +-- On Wed, 3 Jun 2020, Gerd Hoffmann wrote --+ >> | Hmm, why modify mm_index? Shouldn't we just check it is non-zero >> | before calling ati_mm_read/ati_mm_write? >> >> if (s->regs.mm_index & BIT(31)) { >> ... >> } else { >> ati_mm_write(s, s->regs.mm_index + addr - MM_DATA, data, size); >> } >> >> Exit condition for recursion is to set (mm_index & BIT(31)), so recursion >> would continue even with non-zero values I think. > > MM_INDEX and MM_DATA allows access to registers (or memory if BIT(31) is set) > via only these two registers. This is called indexed access in docs. So it > does not really make sense to allow access to these registers as well thus we > can avoid infinite recursion. It's not meant to recurse until BIT(31) is set. > I think you can do: > > if (s->regs.mm_index & BIT(31)) { > ... > - } else { > + } else if (s->regs.mm_index >= BIOS_0_SCRATCH) { Actually this should be + } else if (s->regs.mm_index >= CLOCK_CNTL_INDEX) { or even > MM_DATA + 3 may be best as that only refers to defines used in that case. So maybe + } else if (s->regs.mm_index > MM_DATA + 3) { > ati_mm_write(s, s->regs.mm_index + addr - MM_DATA, data, size); > } > > and do the same in ati_mm_read() as well. > > Regards, > BALATON Zoltan >