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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 004EEC433ED for ; Fri, 9 Apr 2021 08:11:47 +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 7DB7861028 for ; Fri, 9 Apr 2021 08:11:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7DB7861028 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:38386 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lUmF0-0001Uq-JE for qemu-devel@archiver.kernel.org; Fri, 09 Apr 2021 04:11:46 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:42010) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lUmE6-0000uK-1C; Fri, 09 Apr 2021 04:10:50 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:2501) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lUmE3-00086M-1Y; Fri, 09 Apr 2021 04:10:49 -0400 Received: from dggeml405-hub.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4FGrMC1LZRzWPqR; Fri, 9 Apr 2021 16:07:03 +0800 (CST) Received: from dggema765-chm.china.huawei.com (10.1.198.207) by dggeml405-hub.china.huawei.com (10.3.17.49) with Microsoft SMTP Server (TLS) id 14.3.498.0; Fri, 9 Apr 2021 16:10:34 +0800 Received: from [10.174.185.210] (10.174.185.210) by dggema765-chm.china.huawei.com (10.1.198.207) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Fri, 9 Apr 2021 16:10:34 +0800 Subject: Re: A question about the translation granule size supported by the vSMMU To: Auger Eric , Peter Maydell , References: <4886d8d0-cca6-d4b2-4139-29ad52020f79@redhat.com> <0a3ae73c-af3a-9d80-2f30-55424a07d104@redhat.com> From: Kunkun Jiang Message-ID: <15ec88f2-b44b-866b-432a-071e0986d072@huawei.com> Date: Fri, 9 Apr 2021 16:10:23 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <0a3ae73c-af3a-9d80-2f30-55424a07d104@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.174.185.210] X-ClientProxiedBy: dggeme708-chm.china.huawei.com (10.1.199.104) To dggema765-chm.china.huawei.com (10.1.198.207) X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.187; envelope-from=jiangkunkun@huawei.com; helo=szxga01-in.huawei.com 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, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: Zenghui Yu , "wanghaibin.wang@huawei.com" , "open list:ARM SMMU" , Keqian Zhu , "open list:All patches CC here" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Eric, On 2021/4/8 15:27, Auger Eric wrote: > Hi Kunkun, > > On 4/7/21 11:26 AM, Kunkun Jiang wrote: >> Hi Eric, >> >> On 2021/4/7 3:50, Auger Eric wrote: >>> Hi Kunkun, >>> >>> On 3/27/21 3:24 AM, Kunkun Jiang wrote: >>>> Hi all, >>>> >>>> Recently, I did some tests on SMMU nested mode. Here is >>>> a question about the translation granule size supported by >>>> vSMMU. >>>> >>>> There is such a code in SMMUv3_init_regs(): >>>> >>>>>     /* 4K and 64K granule support */ >>>>>      s->idr[5] = FIELD_DP32(s->idr[5], IDR5, GRAN4K, 1); >>>>>      s->idr[5] = FIELD_DP32(s->idr[5], IDR5, GRAN64K, 1); >>>>>      s->idr[5] = FIELD_DP32(s->idr[5], IDR5, OAS, SMMU_IDR5_OAS); /* 44 >>>>> bits */ >>>> Why is the 16K granule not supported? I modified the code >>>> to support it and did not encounter any problems in the >>>> test. Although 4K and 64K minimal granules are "strongly >>>> recommended", I think vSMMU should still support 16K.😉 >>>> Are there other reasons why 16K is not supported here? >>> no there aren't any. The main reasons were 16KB support is optional and >>> supporting it increases the test matrix. Also it seems quite a few >>> machines I have access to do support 16KB granule. On the others I get >>> >>> "EFI stub: ERROR: This 16 KB granular kernel is not supported by your >>> CPU". >>> >>> Nevertheless I am not opposed to support it as it seems to work without >>> trouble. Just need to have an extra look at implied validity checks but >>> there shouldn't be much. >>> >>> Thanks >>> >>> Eric >> Yes, you are right. In my opinion, it is necessary to check whether pSMMU >> supports 16K to avoid the situation I mentioned below. >> In SMMU nested mode, if vSMMU supports 16K and set pasid table to >> pSMMU, it may get errors when pSMMU does translation table walk if >> pSMMU doesn't support 16K (not tested). Do you think we need to add >> an interface to get some pSMMU info?> >> Maybe my consideration was superfluous.😁 > No it is not. At qemu level we have > memory_region_iommu_set_page_size_mask() that is called from the VFIO > device. It allows to pass such info to the IOMMU device (qemu > b91774984249). > > iommu_set_page_size_mask() cb needs to be implemented at SMMU QEMU > device level. Also [PATCH 0/2] Domain nesting info for arm-smmu may > allow to return other constraints from the pSMMU. > > Thanks > > Eric Ok, it makes sense to me. I am glad to test them if these patches are ready. Thanks, Kunkun Jiang >> Thanks, >> Kunkun Jiang >>>> When in SMMU nested mode, it may get errors if pSMMU >>>> doesn't support 16K but vSMMU supports 16K. But we >>>> can get some settings of pSMMU to avoid this situation. >>>> I found some discussions between Eric and Linu about >>>> this [1], but this idea does not seem to be implemented. >>>> >>>> [1] https://lists.gnu.org/archive/html/qemu-arm/2017-09/msg00149.html >>>> >>>> Best regards, >>>> Kunkun Jiang >>>> >>> . >> > .