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=-5.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 AAF52C48BE5 for ; Tue, 22 Jun 2021 15:34:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 939236052B for ; Tue, 22 Jun 2021 15:34:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231876AbhFVPgk (ORCPT ); Tue, 22 Jun 2021 11:36:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232079AbhFVPgk (ORCPT ); Tue, 22 Jun 2021 11:36:40 -0400 Received: from mail-qk1-x734.google.com (mail-qk1-x734.google.com [IPv6:2607:f8b0:4864:20::734]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 19B66C06175F for ; Tue, 22 Jun 2021 08:34:24 -0700 (PDT) Received: by mail-qk1-x734.google.com with SMTP id w21so26743122qkb.9 for ; Tue, 22 Jun 2021 08:34:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=XCGRlJxrxMvSvElmb3McFTndCdFsvf+0ulpFzwibisU=; b=RZ37oQ4xjDFsBnFcY5FzSe7ryg7I2xkkjLJIDG9pWBVE471HjG5oj7ZH9zwFfLGJjb isU5xI2gWvwgcxsSpN4N9oPCNXRQB2asF0okQeuH8sD+dvROpQfY4AHwM98x79x0O5xl ZpXizLnL5TT0sIZB14l2AEL6+cxTu/0iS8e2gKRKGAIznR6ADAbYKgLWRotpG3swQzzG sPAUUbB3nr22lLL4hUjaGnONeGbpSNdzAvtGoWJPME5FmLK3lnJIOmJMwP/op2rBS2Lj 4wFM18A4nUtQ3yo7pekqZd2V3XFmCRuhVmjSEIT1tizi0WIzn3FvnpWdH0taoX8FMvhl NVvQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=XCGRlJxrxMvSvElmb3McFTndCdFsvf+0ulpFzwibisU=; b=Xkwt9ki3lmVHtS7mV6Ilot66SPxzM/9WifODBGiIfGhiNmp6M0qtBZ2TeU35vsxHea 6hIrDoml/s1JHWQ9cNIEgu9mv4zunotHEtTFerMjUPevN+f3cmJnmSx1N6y47O1t4uzO paRwUPSJg48dvCfSlLtHnPk189n8nHbrc7GJn1szeDxcnkYdu2sq2fgNWsSToGvftr6R ngQ2I6S+Br0c9S1GGgqqQSr1TPzIeyQc9HDF0CNhClimvSYBw4ElE7pe66bQggehePl1 Ij8KE5l2VWMRiJxmBTTq7FIAwhwDwGWrp71ttGTM1bZaGZ3NFjltLFOz3mLsyf15wSX6 foOw== X-Gm-Message-State: AOAM5334ADm1Ikg9LYAHyFWStZzuusACfkj98NEdZVqqjQA8GKSSExds HDUn9tGXVWqt2EZKuoywMwrJOQ== X-Google-Smtp-Source: ABdhPJwJRNWHrciXJvuIph1nNbis29uOgjU1s215LhOPous5t6/XyNtN7A0DRMo5coyKAYPFIA6QuA== X-Received: by 2002:a37:a8c1:: with SMTP id r184mr4898379qke.129.1624376063270; Tue, 22 Jun 2021 08:34:23 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-47-55-113-94.dhcp-dynamic.fibreop.ns.bellaliant.net. [47.55.113.94]) by smtp.gmail.com with ESMTPSA id bk38sm7882443qkb.28.2021.06.22.08.34.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Jun 2021 08:34:22 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1lviPu-00ADQh-9q; Tue, 22 Jun 2021 12:34:22 -0300 Date: Tue, 22 Jun 2021 12:34:22 -0300 From: Jason Gunthorpe To: Oded Gabbay Cc: Christian =?utf-8?B?S8O2bmln?= , Gal Pressman , sleybo@amazon.com, linux-rdma , Oded Gabbay , Christoph Hellwig , Linux Kernel Mailing List , dri-devel , Christian =?utf-8?B?S8O2bmln?= , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Doug Ledford , Tomer Tayar , amd-gfx list , Greg KH , Alex Deucher , Leon Romanovsky , "open list:DMA BUFFER SHARING FRAMEWORK" Subject: Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF Message-ID: <20210622153422.GR1096940@ziepe.ca> References: <20210621232912.GK1096940@ziepe.ca> <20210622120142.GL1096940@ziepe.ca> <20210622121546.GN1096940@ziepe.ca> <20210622151142.GA2431880@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Tue, Jun 22, 2021 at 06:24:28PM +0300, Oded Gabbay wrote: > On Tue, Jun 22, 2021 at 6:11 PM Jason Gunthorpe wrote: > > > > On Tue, Jun 22, 2021 at 04:12:26PM +0300, Oded Gabbay wrote: > > > > > > 1) Setting sg_page to NULL > > > > 2) 'mapping' pages for P2P DMA without going through the iommu > > > > 3) Allowing P2P DMA without using the p2p dma API to validate that it > > > > can work at all in the first place. > > > > > > > > All of these result in functional bugs in certain system > > > > configurations. > > > > > > > > Jason > > > > > > Hi Jason, > > > Thanks for the feedback. > > > Regarding point 1, why is that a problem if we disable the option to > > > mmap the dma-buf from user-space ? > > > > Userspace has nothing to do with needing struct pages or not > > > > Point 1 and 2 mostly go together, you supporting the iommu is not nice > > if you dont have struct pages. > > > > You should study Logan's patches I pointed you at as they are solving > > exactly this problem. > Yes, I do need to study them. I agree with you here. It appears I > have a hole in my understanding. I'm missing the connection between > iommu support (which I must have of course) and struct pages. Chistian explained what the AMD driver is doing by calling dma_map_resource(). Which is a hacky and slow way of achieving what Logan's series is doing. > > No, the design of the dmabuf requires the exporter to do the dma maps > > and so it is only the exporter that is wrong to omit all the iommu and > > p2p logic. > > > > RDMA is OK today only because nobody has implemented dma buf support > > in rxe/si - mainly because the only implementations of exporters don't > > Can you please educate me, what is rxe/si ? Sorry, rxe/siw - these are the all-software implementations of RDMA and they require the struct page to do a SW memory copy. They can't implement dmabuf without it. > ok... > so how come that patch-set was merged into 5.12 if it's buggy ? We only implemented true dma devices for RDMA DMABUF support, so it is isn't buggy right now. > Yes, that's what I expect to see. But I want to see it with my own > eyes and then figure out how to solve this. It might be tricky to test because you have to ensure the iommu is turned on and has a non-idenity page table. Basically if it doesn't trigger a IOMMU failure then the IOMMU isn't setup properly. 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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 9BB51C2B9F4 for ; Tue, 22 Jun 2021 15:34:26 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 3A2C060724 for ; Tue, 22 Jun 2021 15:34:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A2C060724 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ziepe.ca Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C236B6E5AE; Tue, 22 Jun 2021 15:34:25 +0000 (UTC) Received: from mail-qk1-x732.google.com (mail-qk1-x732.google.com [IPv6:2607:f8b0:4864:20::732]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1B2B76E5AE for ; Tue, 22 Jun 2021 15:34:24 +0000 (UTC) Received: by mail-qk1-x732.google.com with SMTP id g4so39333809qkl.1 for ; Tue, 22 Jun 2021 08:34:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=XCGRlJxrxMvSvElmb3McFTndCdFsvf+0ulpFzwibisU=; b=RZ37oQ4xjDFsBnFcY5FzSe7ryg7I2xkkjLJIDG9pWBVE471HjG5oj7ZH9zwFfLGJjb isU5xI2gWvwgcxsSpN4N9oPCNXRQB2asF0okQeuH8sD+dvROpQfY4AHwM98x79x0O5xl ZpXizLnL5TT0sIZB14l2AEL6+cxTu/0iS8e2gKRKGAIznR6ADAbYKgLWRotpG3swQzzG sPAUUbB3nr22lLL4hUjaGnONeGbpSNdzAvtGoWJPME5FmLK3lnJIOmJMwP/op2rBS2Lj 4wFM18A4nUtQ3yo7pekqZd2V3XFmCRuhVmjSEIT1tizi0WIzn3FvnpWdH0taoX8FMvhl NVvQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=XCGRlJxrxMvSvElmb3McFTndCdFsvf+0ulpFzwibisU=; b=ia/qPpM7sCe9OJklFhyg5RjjDKmpJNmHflSx+NYsBsD8+FPjTEodIQJNN1SZ4aYuRb ciOOfeGOhNm+ZwicFPkOlcxf6TFlC/XwFEhfMAJEVCKHHn95jKCUUDzjwT08oG5vMMiO AFuxbTD+W65zmUFRwqKMZ4qvkEiQ/3Nrv1fMeKFyZWWa/u6XNlH6ZPfxJhR8C4F7/PWW 6gpWA77pq/hht2NteViDMb4hEQ3pKIAvyk3IUi70nuAz3zk8QviT6U0DWeIRkyQTZ+x0 2J1WU+Nt/7qbDIo0DvY3m1lEJhAr7WdOmm74Ix4UpEsi4X/Xi2UFuGmzLUGqeElnnrla Mz4A== X-Gm-Message-State: AOAM531gN57ysm/mSbDB34eyub8iTsy1fIJpx3F4w2WG0smLNaPg44X4 uyao88MmJEY+QO0KumoeDgwsxw== X-Google-Smtp-Source: ABdhPJwJRNWHrciXJvuIph1nNbis29uOgjU1s215LhOPous5t6/XyNtN7A0DRMo5coyKAYPFIA6QuA== X-Received: by 2002:a37:a8c1:: with SMTP id r184mr4898379qke.129.1624376063270; Tue, 22 Jun 2021 08:34:23 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-47-55-113-94.dhcp-dynamic.fibreop.ns.bellaliant.net. [47.55.113.94]) by smtp.gmail.com with ESMTPSA id bk38sm7882443qkb.28.2021.06.22.08.34.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Jun 2021 08:34:22 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1lviPu-00ADQh-9q; Tue, 22 Jun 2021 12:34:22 -0300 Date: Tue, 22 Jun 2021 12:34:22 -0300 From: Jason Gunthorpe To: Oded Gabbay Subject: Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF Message-ID: <20210622153422.GR1096940@ziepe.ca> References: <20210621232912.GK1096940@ziepe.ca> <20210622120142.GL1096940@ziepe.ca> <20210622121546.GN1096940@ziepe.ca> <20210622151142.GA2431880@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Christian =?utf-8?B?S8O2bmln?= , linux-rdma , Christian =?utf-8?B?S8O2bmln?= , sleybo@amazon.com, Gal Pressman , dri-devel , Christoph Hellwig , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Doug Ledford , Tomer Tayar , amd-gfx list , Greg KH , Alex Deucher , Leon Romanovsky , Oded Gabbay , Linux Kernel Mailing List , "open list:DMA BUFFER SHARING FRAMEWORK" Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Jun 22, 2021 at 06:24:28PM +0300, Oded Gabbay wrote: > On Tue, Jun 22, 2021 at 6:11 PM Jason Gunthorpe wrote: > > > > On Tue, Jun 22, 2021 at 04:12:26PM +0300, Oded Gabbay wrote: > > > > > > 1) Setting sg_page to NULL > > > > 2) 'mapping' pages for P2P DMA without going through the iommu > > > > 3) Allowing P2P DMA without using the p2p dma API to validate that it > > > > can work at all in the first place. > > > > > > > > All of these result in functional bugs in certain system > > > > configurations. > > > > > > > > Jason > > > > > > Hi Jason, > > > Thanks for the feedback. > > > Regarding point 1, why is that a problem if we disable the option to > > > mmap the dma-buf from user-space ? > > > > Userspace has nothing to do with needing struct pages or not > > > > Point 1 and 2 mostly go together, you supporting the iommu is not nice > > if you dont have struct pages. > > > > You should study Logan's patches I pointed you at as they are solving > > exactly this problem. > Yes, I do need to study them. I agree with you here. It appears I > have a hole in my understanding. I'm missing the connection between > iommu support (which I must have of course) and struct pages. Chistian explained what the AMD driver is doing by calling dma_map_resource(). Which is a hacky and slow way of achieving what Logan's series is doing. > > No, the design of the dmabuf requires the exporter to do the dma maps > > and so it is only the exporter that is wrong to omit all the iommu and > > p2p logic. > > > > RDMA is OK today only because nobody has implemented dma buf support > > in rxe/si - mainly because the only implementations of exporters don't > > Can you please educate me, what is rxe/si ? Sorry, rxe/siw - these are the all-software implementations of RDMA and they require the struct page to do a SW memory copy. They can't implement dmabuf without it. > ok... > so how come that patch-set was merged into 5.12 if it's buggy ? We only implemented true dma devices for RDMA DMABUF support, so it is isn't buggy right now. > Yes, that's what I expect to see. But I want to see it with my own > eyes and then figure out how to solve this. It might be tricky to test because you have to ensure the iommu is turned on and has a non-idenity page table. Basically if it doesn't trigger a IOMMU failure then the IOMMU isn't setup properly. 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[47.55.113.94]) by smtp.gmail.com with ESMTPSA id bk38sm7882443qkb.28.2021.06.22.08.34.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Jun 2021 08:34:22 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1lviPu-00ADQh-9q; Tue, 22 Jun 2021 12:34:22 -0300 Date: Tue, 22 Jun 2021 12:34:22 -0300 From: Jason Gunthorpe To: Oded Gabbay Subject: Re: [Linaro-mm-sig] [PATCH v3 1/2] habanalabs: define uAPI to export FD for DMA-BUF Message-ID: <20210622153422.GR1096940@ziepe.ca> References: <20210621232912.GK1096940@ziepe.ca> <20210622120142.GL1096940@ziepe.ca> <20210622121546.GN1096940@ziepe.ca> <20210622151142.GA2431880@ziepe.ca> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mailman-Approved-At: Tue, 22 Jun 2021 17:13:59 +0000 X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Christian =?utf-8?B?S8O2bmln?= , linux-rdma , Christian =?utf-8?B?S8O2bmln?= , sleybo@amazon.com, Gal Pressman , dri-devel , Christoph Hellwig , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Doug Ledford , Tomer Tayar , amd-gfx list , Greg KH , Alex Deucher , Leon Romanovsky , Oded Gabbay , Linux Kernel Mailing List , "open list:DMA BUFFER SHARING FRAMEWORK" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" On Tue, Jun 22, 2021 at 06:24:28PM +0300, Oded Gabbay wrote: > On Tue, Jun 22, 2021 at 6:11 PM Jason Gunthorpe wrote: > > > > On Tue, Jun 22, 2021 at 04:12:26PM +0300, Oded Gabbay wrote: > > > > > > 1) Setting sg_page to NULL > > > > 2) 'mapping' pages for P2P DMA without going through the iommu > > > > 3) Allowing P2P DMA without using the p2p dma API to validate that it > > > > can work at all in the first place. > > > > > > > > All of these result in functional bugs in certain system > > > > configurations. > > > > > > > > Jason > > > > > > Hi Jason, > > > Thanks for the feedback. > > > Regarding point 1, why is that a problem if we disable the option to > > > mmap the dma-buf from user-space ? > > > > Userspace has nothing to do with needing struct pages or not > > > > Point 1 and 2 mostly go together, you supporting the iommu is not nice > > if you dont have struct pages. > > > > You should study Logan's patches I pointed you at as they are solving > > exactly this problem. > Yes, I do need to study them. I agree with you here. It appears I > have a hole in my understanding. I'm missing the connection between > iommu support (which I must have of course) and struct pages. Chistian explained what the AMD driver is doing by calling dma_map_resource(). Which is a hacky and slow way of achieving what Logan's series is doing. > > No, the design of the dmabuf requires the exporter to do the dma maps > > and so it is only the exporter that is wrong to omit all the iommu and > > p2p logic. > > > > RDMA is OK today only because nobody has implemented dma buf support > > in rxe/si - mainly because the only implementations of exporters don't > > Can you please educate me, what is rxe/si ? Sorry, rxe/siw - these are the all-software implementations of RDMA and they require the struct page to do a SW memory copy. They can't implement dmabuf without it. > ok... > so how come that patch-set was merged into 5.12 if it's buggy ? We only implemented true dma devices for RDMA DMABUF support, so it is isn't buggy right now. > Yes, that's what I expect to see. But I want to see it with my own > eyes and then figure out how to solve this. It might be tricky to test because you have to ensure the iommu is turned on and has a non-idenity page table. Basically if it doesn't trigger a IOMMU failure then the IOMMU isn't setup properly. Jason _______________________________________________ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx