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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 A8092CA90AF for ; Wed, 13 May 2020 11:32:40 +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 7481A206D6 for ; Wed, 13 May 2020 11:32:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DaFkKBZJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7481A206D6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:55974 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jYpct-0004QS-Ik for qemu-devel@archiver.kernel.org; Wed, 13 May 2020 07:32:39 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56832) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jYpRl-0001vp-3H for qemu-devel@nongnu.org; Wed, 13 May 2020 07:21:09 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:46510 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jYpRi-0006R5-M5 for qemu-devel@nongnu.org; Wed, 13 May 2020 07:21:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589368865; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=QuEqRupYE5OjBe7MH68MRWjpGHUpJmPaF+5jOcJraX0=; b=DaFkKBZJL7vQbxd4K6Xj4CJl2xasCpYVkwgdiYziYsQKYm77CALPLSvK8afVJPjfWb3vCV s0CCjzFoSsVokcv1Mg7N42sC4kQh6lQjRhanKe8AfOeZthbn5EWtgiTgPqdwKppufcU2hX a1EmKA+hUpMLNhvrRT/98Qqhx74yPtg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-388-ENMldBJzNlO9ZztFobBqFg-1; Wed, 13 May 2020 07:21:03 -0400 X-MC-Unique: ENMldBJzNlO9ZztFobBqFg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AB2DB100CCC2; Wed, 13 May 2020 11:21:02 +0000 (UTC) Received: from kaapi (unknown [10.74.9.109]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 145F26E6FC; Wed, 13 May 2020 11:20:57 +0000 (UTC) Date: Wed, 13 May 2020 16:50:52 +0530 (IST) From: P J P X-X-Sender: pjp@kaapi To: Peter Maydell Subject: Re: [PATCH 1/2] megasas: use unsigned type for reply_queue_head In-Reply-To: Message-ID: References: <20200507105718.1319187-1-ppandit@redhat.com> <20200507105718.1319187-2-ppandit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Received-SPF: pass client-ip=205.139.110.61; envelope-from=ppandit@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/13 01:56:38 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, 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: Fam Zheng , Paolo Bonzini , QEMU Developers , Ren Ding Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" +-- On Tue, 12 May 2020, Peter Maydell wrote --+ | > + uint16_t reply_queue_head; | | Using a 16-bit type here means that code like this: | | s->reply_queue_head = ldl_le_pci_dma(pcid, s->producer_pa); | s->reply_queue_head %= MEGASAS_MAX_FRAMES; | | suddenly does a truncation of the 32-bit loaded value before | the modulus operation, which is a bit odd, though since | MEGASAS_MAX_FRAMES happens to be a power of 2 the end | result won't change. Yes, 16-bit also for its range of value is limitted to MEGASAS_MAX_FRAMES=2048. | It's also a bit weird to change reply_queue_head's type | but not reply_queue_tail or reply_queue_len. That's in the second patch. Thank you. -- Prasad J Pandit / Red Hat Product Security Team 8685 545E B54C 486B C6EB 271E E285 8B5A F050 DE8D