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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 907DEC433FE for ; Tue, 4 Oct 2022 16:13:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229986AbiJDQN3 (ORCPT ); Tue, 4 Oct 2022 12:13:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41286 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229564AbiJDQN1 (ORCPT ); Tue, 4 Oct 2022 12:13:27 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63FB12C124; Tue, 4 Oct 2022 09:13:26 -0700 (PDT) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 294FkmJp010878; Tue, 4 Oct 2022 16:13:16 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : subject : from : to : cc : date : in-reply-to : references : content-type : content-transfer-encoding : mime-version; s=pp1; bh=46SayH01nZ7idobg+tOSIbfFlcDN1QkIJq1FYmwpg8Q=; b=lUJtP8d4aT/OVLw3JW6A+ZrQ6R+fKPaB3NtVi+/qHIhwK2cFR3ZG4tc+Qw8UUVS/g9IS DgYT5BZgauixcbXAYPSOJyUxStaDy+qONFtuo8B0dt0hBBslWU2l999A21lIn0u/BFn6 k4DCm8miq0TP01ZBWNxIFVILn7Vu0mbkDgvV/oKiqfjqOeoBKYexJf1CtJ0Qq0HLih+A mauOyIVZB6ExWuSnT1Y3Apcmw1CPFGJWR7k6hxXd54zkmAqoHNqYSoZ+L+96RrPg7VCP bGEv2Z16UT+IKEsBDm7A4fTkeBeZ2eCQubFzUDHLxjgTXXfvHtMskGhak+QJU47ysP1L jQ== Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3k0fsn090p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 04 Oct 2022 16:13:15 +0000 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 294G64VA017682; Tue, 4 Oct 2022 16:13:13 GMT Received: from b06avi18626390.portsmouth.uk.ibm.com (b06avi18626390.portsmouth.uk.ibm.com [9.149.26.192]) by ppma06ams.nl.ibm.com with ESMTP id 3jxctj4etu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 04 Oct 2022 16:13:13 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 294G8f6F50004270 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 4 Oct 2022 16:08:41 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2A2C811C04A; Tue, 4 Oct 2022 16:13:10 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 77DF511C04C; Tue, 4 Oct 2022 16:13:09 +0000 (GMT) Received: from sig-9-145-21-9.uk.ibm.com (unknown [9.145.21.9]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 4 Oct 2022 16:13:09 +0000 (GMT) Message-ID: <0da03411190c004e85cc856965b0aca901fd78fb.camel@linux.ibm.com> Subject: Re: [PATCH v4 5/5] iommu/s390: Fix incorrect pgsize_bitmap From: Niklas Schnelle To: Robin Murphy , Matthew Rosato , Pierre Morel , iommu@lists.linux.dev Cc: linux-s390@vger.kernel.org, borntraeger@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, gerald.schaefer@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com, joro@8bytes.org, will@kernel.org, jgg@nvidia.com, linux-kernel@vger.kernel.org Date: Tue, 04 Oct 2022 18:13:09 +0200 In-Reply-To: References: <20221004120706.2957492-1-schnelle@linux.ibm.com> <20221004120706.2957492-6-schnelle@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-18.el8) X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: _EhYxTJ-zUdsJ2mF6sGVTORYpyIgjgig X-Proofpoint-GUID: _EhYxTJ-zUdsJ2mF6sGVTORYpyIgjgig Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1 definitions=2022-10-04_06,2022-09-29_03,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 clxscore=1015 suspectscore=0 phishscore=0 spamscore=0 priorityscore=1501 malwarescore=0 mlxlogscore=999 impostorscore=0 mlxscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2209130000 definitions=main-2210040104 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2022-10-04 at 16:31 +0100, Robin Murphy wrote: > On 2022-10-04 16:12, Matthew Rosato wrote: > > On 10/4/22 11:02 AM, Robin Murphy wrote: > > > On 2022-10-04 13:07, Niklas Schnelle wrote: > > > > The .pgsize_bitmap property of struct iommu_ops is not a page mask but > > > > rather has a bit set for each size of pages the IOMMU supports. As the > > > > comment correctly pointed out at this moment the code only support 4K > > > > pages so simply use SZ_4K here. > > > > > > Unless it's already been done somewhere else, you'll want to switch over to the {map,unmap}_pages() interfaces as well to avoid taking a hit on efficiency here. The "page mask" thing was an old hack to trick the core API into making fewer map/unmap calls where the driver could map arbitrary numbers of pages at once anyway. The multi-page interfaces now do that more honestly and generally better (since they work for non-power-of-two sizes as well). > > > > Thanks for the heads up -- Niklas has some additional series coming soon as described here: > > > > https://lore.kernel.org/linux-iommu/a10424adbe01a0fd40372cbd0736d11e517951a1.camel@linux.ibm.com/ > > > > So implementing the _pages() interfaces is soon up on the roadmap. But given what you say I wonder if this patch should just wait until the series that implements {map,unmap}_pages(). > > Perhaps, although the full change should be trivial enough that there's > probably just as much argument for doing the whole thing in its own > right for the sake of this cleanup. The main point is that > S390_IOMMU_PGSIZES is not incorrect as such, it's just not spelling out > the deliberate trick that it's achieving - everyone copied it from > intel-iommu, but since that got converted to the new interfaces the > original explanation is now gone. The only effect of "fixing" it in > isolation right now will be to make large VFIO mappings slower. > > Robin. The patch changing to map_pages()/unmap_pages() is currently part of a larger series of improvements, some of which are less trivial. So I'm planning to send those as RFC first. Those include changing the spin_lock protected list to RCU so the map/unmap can paralellize better. Another one is atomic updates to the IOMMU tables to do away with locks in map/unmap. So I think pulling that whole series into this one isn't ideal. I could pull just the map_pages()/unmap_pages() change though. > > > > > Reviewed-by: Jason Gunthorpe > > > > Signed-off-by: Niklas Schnelle > > > > --- > > > > drivers/iommu/s390-iommu.c | 9 +-------- > > > > 1 file changed, 1 insertion(+), 8 deletions(-) > > > > > > > > diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c > > > > index 94c444b909bd..6bf23e7830a2 100644 > > > > --- a/drivers/iommu/s390-iommu.c > > > > +++ b/drivers/iommu/s390-iommu.c > > > > @@ -12,13 +12,6 @@ > > > > #include > > > > #include > > > > -/* > > > > - * Physically contiguous memory regions can be mapped with 4 KiB alignment, > > > > - * we allow all page sizes that are an order of 4KiB (no special large page > > > > - * support so far). > > > > - */ > > > > -#define S390_IOMMU_PGSIZES (~0xFFFUL) > > > > - > > > > static const struct iommu_ops s390_iommu_ops; > > > > struct s390_domain { > > > > @@ -350,7 +343,7 @@ static const struct iommu_ops s390_iommu_ops = { > > > > .probe_device = s390_iommu_probe_device, > > > > .release_device = s390_iommu_release_device, > > > > .device_group = generic_device_group, > > > > - .pgsize_bitmap = S390_IOMMU_PGSIZES, > > > > + .pgsize_bitmap = SZ_4K, > > > > .get_resv_regions = s390_iommu_get_resv_regions, > > > > .default_domain_ops = &(const struct iommu_domain_ops) { > > > > .attach_dev = s390_iommu_attach_device,