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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50369C433EF for ; Thu, 7 Oct 2021 11:55:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 33BED61251 for ; Thu, 7 Oct 2021 11:55:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241127AbhJGL5E (ORCPT ); Thu, 7 Oct 2021 07:57:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47844 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230091AbhJGL46 (ORCPT ); Thu, 7 Oct 2021 07:56:58 -0400 Received: from mail-ed1-x531.google.com (mail-ed1-x531.google.com [IPv6:2a00:1450:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 449C0C061746 for ; Thu, 7 Oct 2021 04:55:05 -0700 (PDT) Received: by mail-ed1-x531.google.com with SMTP id z20so22000634edc.13 for ; Thu, 07 Oct 2021 04:55:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2Sc46Q9eMcwlaMy2IZJgD2QwpVCcYg9+SD8cXYZgbr4=; b=RT9YmSKnUjHCEr3v6bar51e1fzGq7K8YE+IB7ejWFNs9jODGQtkmWkzq2hgZujJCUJ mnennI/hqWHn0R1mtQCCEqvymetd/bl2VgplLcGb/U/N0sjVCoyKEwx/mkoc9MmETaWb ceVbHfdd9xnvcaN9u+osChdyCUu9BQJsE2WJ1gkkcj9kLDP7jXmcIiWdLsxl9rKdDTIf H3EuUUBia7VJlzi8PEgVftWKFBtcQ65f0EUzVoBGCFv1cdIyTgp1RMdXi/gD1rVfq7g4 IPgNqk9yxnkGrT6gy6s2iNHiSDmFQpfjA2B5eyN0gQHdihyPlscJUjXMjZzUJB7bbr1L Wh+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2Sc46Q9eMcwlaMy2IZJgD2QwpVCcYg9+SD8cXYZgbr4=; b=b+r0j8zgoGD/67gKWdA1IyWZM3UuWtSmfA/RPy/Kqy+1SD9+x0911naFckurk08tSf K7f6DDdHlyg0FmIAAYG6CZt/oxXj4G8UPv5jKG7jY3aQC8n0QG90iXbdJdbKDObSr1Hd 5Y8I96uTOwcCmK4JULDohsTAmHNNYEbr6V9FaS0tVQTrjpEUCj7U4im0O04DGsHDLUCv XSCEzXmIjM1eMPnOjhOJmG01lBZnL7rzUtzQpmZmOhLtojHlZuTk/4PyUEocgTYWXSzd TlPIB9LNaj+s2LIcNZJon2S5tmcXmMDVK5r5E6MUoDL57Jix0AVKHHEhk9sh74vOTsrZ plUA== X-Gm-Message-State: AOAM530eFI+IEdsB3lNxTEaSmQPspJvZT7Hy/ysZXIOqfQPlDuJ1Hq4u CWCdTdIFunujNZF1jfme6sCfYWMElFgGiFI15BY= X-Google-Smtp-Source: ABdhPJyCXK/u3V2xMWIJIiVDE8gg9vaOTOj4ckAKIeY5EmY50zW1eFNxbthRtAZ1ldJbNFWWIlCpZCQBCqK/PKY06k8= X-Received: by 2002:a17:906:3383:: with SMTP id v3mr5173329eja.213.1633607703888; Thu, 07 Oct 2021 04:55:03 -0700 (PDT) MIME-Version: 1.0 References: <1632256181-36071-1-git-send-email-jacob.jun.pan@linux.intel.com> <20211001123623.GM964074@nvidia.com> <20211004094003.527222e5@jacob-builder> <20211004182142.GM964074@nvidia.com> <20211007113221.GF2744544@nvidia.com> In-Reply-To: <20211007113221.GF2744544@nvidia.com> From: Barry Song <21cnbao@gmail.com> Date: Fri, 8 Oct 2021 00:54:52 +1300 Message-ID: Subject: Re: [RFC 0/7] Support in-kernel DMA with PASID and SVA To: Jason Gunthorpe Cc: Jacob Pan , iommu@lists.linux-foundation.org, LKML , Joerg Roedel , Christoph Hellwig , Lu Baolu , Raj Ashok , "Kumar, Sanjay K" , Dave Jiang , Tony Luck , mike.campin@intel.com, Yi Liu , "Tian, Kevin" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 8, 2021 at 12:32 AM Jason Gunthorpe wrote: > > On Thu, Oct 07, 2021 at 06:43:33PM +1300, Barry Song wrote: > > > So do we have a case where devices can directly access the kernel's data > > structure such as a list/graph/tree with pointers to a kernel virtual address? > > then devices don't need to translate the address of pointers in a structure. > > I assume this is one of the most useful features userspace SVA can provide. > > AFIACT that is the only good case for KVA, but it is also completely > against the endianess, word size and DMA portability design of the > kernel. > > Going there requires some new set of portable APIs for gobally > coherent KVA dma. yep. I agree. it would be very weird if accelerators/gpu are sharing kernel' data struct, but for each "DMA" operation - reading or writing the data struct, we have to call dma_map_single/sg or dma_sync_single_for_cpu/device etc. It seems once devices and cpus are sharing virtual address(SVA), code doesn't need to do explicit map/sync each time. > > Jason Thanks barry