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Sun, 06 Jun 2021 20:18:42 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id w10sm6719572pfg.196.2021.06.06.20.18.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 06 Jun 2021 20:18:42 -0700 (PDT) Subject: Re: [RFC] /dev/ioasid uAPI proposal To: Jason Gunthorpe Cc: Alex Williamson , "Tian, Kevin" , Jean-Philippe Brucker , "Jiang, Dave" , "Raj, Ashok" , "kvm@vger.kernel.org" , Jonathan Corbet , Robin Murphy , LKML , "iommu@lists.linux-foundation.org" , David Gibson , Kirti Wankhede , David Woodhouse References: <20210602111117.026d4a26.alex.williamson@redhat.com> <20210602173510.GE1002214@nvidia.com> <20210602120111.5e5bcf93.alex.williamson@redhat.com> <20210602180925.GH1002214@nvidia.com> <20210602130053.615db578.alex.williamson@redhat.com> <20210602195404.GI1002214@nvidia.com> <20210602143734.72fb4fa4.alex.williamson@redhat.com> <6a9426d7-ed55-e006-9c4c-6b7c78142e39@redhat.com> <20210603130927.GZ1002214@nvidia.com> <65614634-1db4-7119-1a90-64ba5c6e9042@redhat.com> <20210604115805.GG1002214@nvidia.com> From: Jason Wang Message-ID: <895671cc-5ef8-bc1a-734c-e9e2fdf03652@redhat.com> Date: Mon, 7 Jun 2021 11:18:33 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210604115805.GG1002214@nvidia.com> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ÔÚ 2021/6/4 ÏÂÎç7:58, Jason Gunthorpe дµÀ: > On Fri, Jun 04, 2021 at 09:11:03AM +0800, Jason Wang wrote: >>> nor do any virtio drivers implement the required platform specific >>> cache flushing to make no-snoop TLPs work. >> I don't get why virtio drivers needs to do that. I think DMA API should hide >> those arch/platform specific stuffs from us. > It is not arch/platform stuff. If the device uses no-snoop then a > very platform specific recovery is required in the device driver. > > It is not part of the normal DMA API, it is side APIs like > flush_agp_cache() or wbinvd() that are used by GPU drivers only. Yes and virtio doesn't support AGP. > > If drivers/virtio doesn't explicitly call these things it doesn't > support no-snoop - hence no VDPA device can ever use no-snoop. Note that no drivers call these things doesn't meant it was not supported by the spec. Actually, spec doesn't forbid the non coherent DMA, anyway we can raise a new thread in the virtio mailing list to discuss about that. But consider virtio has already supported GPU, crypto and sound device, and the devices like codec and video are being proposed. It doesn't help if we mandate coherent DMA now. Thanks > > Since VIRTIO_F_ACCESS_PLATFORM doesn't trigger wbinvd on x86 it has > nothing to do with no-snoop. > > Jason > 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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, 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 EA012C4743E for ; Mon, 7 Jun 2021 03:18:55 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 7C8F76120D for ; Mon, 7 Jun 2021 03:18:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7C8F76120D Authentication-Results: mail.kernel.org; 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Sun, 06 Jun 2021 20:18:42 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzxyhCGMAJgmD0wCDBmip4ixPdmhcn5mWCmYZELjB4tRm0TDYopxIzBxkopd2Rpl9Ugu+p2EA== X-Received: by 2002:a17:90a:390d:: with SMTP id y13mr18291758pjb.52.1623035922656; Sun, 06 Jun 2021 20:18:42 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id w10sm6719572pfg.196.2021.06.06.20.18.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 06 Jun 2021 20:18:42 -0700 (PDT) Subject: Re: [RFC] /dev/ioasid uAPI proposal To: Jason Gunthorpe References: <20210602111117.026d4a26.alex.williamson@redhat.com> <20210602173510.GE1002214@nvidia.com> <20210602120111.5e5bcf93.alex.williamson@redhat.com> <20210602180925.GH1002214@nvidia.com> <20210602130053.615db578.alex.williamson@redhat.com> <20210602195404.GI1002214@nvidia.com> <20210602143734.72fb4fa4.alex.williamson@redhat.com> <6a9426d7-ed55-e006-9c4c-6b7c78142e39@redhat.com> <20210603130927.GZ1002214@nvidia.com> <65614634-1db4-7119-1a90-64ba5c6e9042@redhat.com> <20210604115805.GG1002214@nvidia.com> From: Jason Wang Message-ID: <895671cc-5ef8-bc1a-734c-e9e2fdf03652@redhat.com> Date: Mon, 7 Jun 2021 11:18:33 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210604115805.GG1002214@nvidia.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Cc: Jean-Philippe Brucker , "Tian, Kevin" , "Jiang, Dave" , "Raj, Ashok" , "kvm@vger.kernel.org" , Jonathan Corbet , David Woodhouse , LKML , "iommu@lists.linux-foundation.org" , Alex Williamson , Kirti Wankhede , Robin Murphy , David Gibson X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: base64 Content-Type: text/plain; charset="gbk"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" CtTaIDIwMjEvNi80IM/Czuc3OjU4LCBKYXNvbiBHdW50aG9ycGUg0LS1wDoKPiBPbiBGcmksIEp1 biAwNCwgMjAyMSBhdCAwOToxMTowM0FNICswODAwLCBKYXNvbiBXYW5nIHdyb3RlOgo+Pj4gbm9y IGRvIGFueSB2aXJ0aW8gZHJpdmVycyBpbXBsZW1lbnQgdGhlIHJlcXVpcmVkIHBsYXRmb3JtIHNw ZWNpZmljCj4+PiBjYWNoZSBmbHVzaGluZyB0byBtYWtlIG5vLXNub29wIFRMUHMgd29yay4KPj4g SSBkb24ndCBnZXQgd2h5IHZpcnRpbyBkcml2ZXJzIG5lZWRzIHRvIGRvIHRoYXQuIEkgdGhpbmsg RE1BIEFQSSBzaG91bGQgaGlkZQo+PiB0aG9zZSBhcmNoL3BsYXRmb3JtIHNwZWNpZmljIHN0dWZm cyBmcm9tIHVzLgo+IEl0IGlzIG5vdCBhcmNoL3BsYXRmb3JtIHN0dWZmLiBJZiB0aGUgZGV2aWNl IHVzZXMgbm8tc25vb3AgdGhlbiBhCj4gdmVyeSBwbGF0Zm9ybSBzcGVjaWZpYyByZWNvdmVyeSBp cyByZXF1aXJlZCBpbiB0aGUgZGV2aWNlIGRyaXZlci4KPgo+IEl0IGlzIG5vdCBwYXJ0IG9mIHRo ZSBub3JtYWwgRE1BIEFQSSwgaXQgaXMgc2lkZSBBUElzIGxpa2UKPiBmbHVzaF9hZ3BfY2FjaGUo KSBvciB3YmludmQoKSB0aGF0IGFyZSB1c2VkIGJ5IEdQVSBkcml2ZXJzIG9ubHkuCgoKWWVzIGFu ZCB2aXJ0aW8gZG9lc24ndCBzdXBwb3J0IEFHUC4KCgo+Cj4gSWYgZHJpdmVycy92aXJ0aW8gZG9l c24ndCBleHBsaWNpdGx5IGNhbGwgdGhlc2UgdGhpbmdzIGl0IGRvZXNuJ3QKPiBzdXBwb3J0IG5v LXNub29wIC0gaGVuY2Ugbm8gVkRQQSBkZXZpY2UgY2FuIGV2ZXIgdXNlIG5vLXNub29wLgoKCk5v dGUgdGhhdCBubyBkcml2ZXJzIGNhbGwgdGhlc2UgdGhpbmdzIGRvZXNuJ3QgbWVhbnQgaXQgd2Fz IG5vdCAKc3VwcG9ydGVkIGJ5IHRoZSBzcGVjLgoKQWN0dWFsbHksIHNwZWMgZG9lc24ndCBmb3Ji aWQgdGhlIG5vbiBjb2hlcmVudCBETUEsIGFueXdheSB3ZSBjYW4gcmFpc2UgCmEgbmV3IHRocmVh ZCBpbiB0aGUgdmlydGlvIG1haWxpbmcgbGlzdCB0byBkaXNjdXNzIGFib3V0IHRoYXQuCgpCdXQg Y29uc2lkZXIgdmlydGlvIGhhcyBhbHJlYWR5IHN1cHBvcnRlZCBHUFUsIGNyeXB0byBhbmQgc291 bmQgZGV2aWNlLCAKYW5kIHRoZSBkZXZpY2VzIGxpa2UgY29kZWMgYW5kIHZpZGVvIGFyZSBiZWlu ZyBwcm9wb3NlZC4gSXQgZG9lc24ndCBoZWxwIAppZiB3ZSBtYW5kYXRlIGNvaGVyZW50IERNQSBu b3cuCgpUaGFua3MKCgo+Cj4gU2luY2UgVklSVElPX0ZfQUNDRVNTX1BMQVRGT1JNIGRvZXNuJ3Qg dHJpZ2dlciB3YmludmQgb24geDg2IGl0IGhhcwo+IG5vdGhpbmcgdG8gZG8gd2l0aCBuby1zbm9v cC4KPgo+IEphc29uCj4KCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fCmlvbW11IG1haWxpbmcgbGlzdAppb21tdUBsaXN0cy5saW51eC1mb3VuZGF0aW9uLm9y ZwpodHRwczovL2xpc3RzLmxpbnV4Zm91bmRhdGlvbi5vcmcvbWFpbG1hbi9saXN0aW5mby9pb21t dQ==