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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 7B3C0C282C0 for ; Wed, 23 Jan 2019 09:04:25 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 00BC420861 for ; Wed, 23 Jan 2019 09:04:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 00BC420861 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 43kzqq0cf2zDqMb for ; Wed, 23 Jan 2019 20:04:23 +1100 (AEDT) Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 43kzp23R8MzDqDD for ; Wed, 23 Jan 2019 20:02:50 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from ozlabs.org (bilbo.ozlabs.org [203.11.71.1]) by bilbo.ozlabs.org (Postfix) with ESMTP id 43kzp22JD6z8t7p for ; Wed, 23 Jan 2019 20:02:50 +1100 (AEDT) Received: by ozlabs.org (Postfix) id 43kzp21xVhz9s9h; Wed, 23 Jan 2019 20:02:50 +1100 (AEDT) Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=aneesh.kumar@linux.ibm.com; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 43kzp15GZHz9s9G for ; Wed, 23 Jan 2019 20:02:49 +1100 (AEDT) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x0N8x0KD085600 for ; Wed, 23 Jan 2019 04:02:48 -0500 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2q6mktsmsm-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 23 Jan 2019 04:02:48 -0500 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 23 Jan 2019 09:02:42 -0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x0N92fWb28573838 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 23 Jan 2019 09:02:41 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A7EE411C06E; Wed, 23 Jan 2019 09:02:41 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8838911C050; Wed, 23 Jan 2019 09:02:40 +0000 (GMT) Received: from skywalker.linux.ibm.com (unknown [9.85.69.250]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 23 Jan 2019 09:02:40 +0000 (GMT) X-Mailer: emacs 26.1 (via feedmail 11-beta-1 I) From: "Aneesh Kumar K.V" To: Michael Ellerman , linuxppc-dev@ozlabs.org Subject: Re: [PATCH 2/4] powerpc/64s: Add slb_full_bitmap rather than hard-coding U32_MAX In-Reply-To: <20190117121328.13395-2-mpe@ellerman.id.au> References: <20190117121328.13395-1-mpe@ellerman.id.au> <20190117121328.13395-2-mpe@ellerman.id.au> Date: Wed, 23 Jan 2019 14:32:38 +0530 MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 x-cbid: 19012309-0028-0000-0000-0000033CEAFC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19012309-0029-0000-0000-000023FA27A7 Message-Id: <871s53d9w1.fsf@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-01-23_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1901230070 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: npiggin@gmail.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Michael Ellerman writes: > The recent rewrite of the SLB code into C included the assumption that > all CPUs we run on have at least 32 SLB entries. This is currently > true but a bit fragile as the SLB size is actually defined by the > device tree and so could theoretically change at any time. > > The assumption is encoded in the fact that we use U32_MAX as the value > for a full SLB bitmap. Instead, calculate what the full bitmap would > be based on the SLB size we're given and store it. This still requires > the SLB size to be a power of 2. So if it is less than 32 we want to make sure we don't allocate an index above 32. Is this the reason for that radom assert_slb_presence? Reviewed-by: Aneesh Kumar K.V > > Fixes: 126b11b294d1 ("powerpc/64s/hash: Add SLB allocation status bitmaps") > Signed-off-by: Michael Ellerman > --- > arch/powerpc/mm/slb.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c > index bc3914d54e26..61450a9cf30d 100644 > --- a/arch/powerpc/mm/slb.c > +++ b/arch/powerpc/mm/slb.c > @@ -506,9 +506,16 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm) > asm volatile("isync" : : : "memory"); > } > > +static u32 slb_full_bitmap; > + > void slb_set_size(u16 size) > { > mmu_slb_size = size; > + > + if (size >= 32) > + slb_full_bitmap = U32_MAX; > + else > + slb_full_bitmap = (1ul << size) - 1; > } > > void slb_initialize(void) > @@ -611,7 +618,7 @@ static enum slb_index alloc_slb_index(bool kernel) > * POWER7/8/9 have 32 SLB entries, this could be expanded if a > * future CPU has more. > */ > - if (local_paca->slb_used_bitmap != U32_MAX) { > + if (local_paca->slb_used_bitmap != slb_full_bitmap) { > index = ffz(local_paca->slb_used_bitmap); > local_paca->slb_used_bitmap |= 1U << index; > if (kernel) > -- > 2.20.1