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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 C1B66C433E0 for ; Fri, 19 Jun 2020 01:57:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9633120890 for ; Fri, 19 Jun 2020 01:57:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="RWByl3EN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728573AbgFSB5v (ORCPT ); Thu, 18 Jun 2020 21:57:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727909AbgFSB5t (ORCPT ); Thu, 18 Jun 2020 21:57:49 -0400 Received: from mail-qv1-xf42.google.com (mail-qv1-xf42.google.com [IPv6:2607:f8b0:4864:20::f42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 81D3CC06174E for ; Thu, 18 Jun 2020 18:57:49 -0700 (PDT) Received: by mail-qv1-xf42.google.com with SMTP id x16so3780750qvr.3 for ; Thu, 18 Jun 2020 18:57:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=YgKJItMU5Ff8V+3ai9lauxHDNq0p9UYzRxSaQNNeJ78=; b=RWByl3ENWb+jOZcDgX5pjEQAcMojM1p5Y0+ztpc2KlCAruuFO0jb3/zm0T2DYQ/O0V M/TialO9NZB6LC6NFquHPnJ48hCy8/Si2jNLrWtWIIYTD1PPTbqZ/FUTJUW9M7MlAweF NORZKUeVmY7WrSL0AGtsUXelno+p++3PhCrlw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=YgKJItMU5Ff8V+3ai9lauxHDNq0p9UYzRxSaQNNeJ78=; b=mrlAR2TlHX8pJLBsPRfPsUFEeU775jUsUom6z76cNPmfxOF28MxnkNSkKpbzO8O+5z 1LVI38Tmk3o/2n4H/GgMUE2j06k/RggzSFJDnCvCrPF4g6ULkOkMOXU1L+IbQbd6dW3E qC1a2FyAOoYx7i0XUXRezG6qOSDHYIjtHzI4VixQcPkb/VPzrqly5IDl31BfIrh6tjFn vwwxhJ/4hg9kesGbKThPhrhS2m4Y3brnBTaPVtGFyfpiFdaDQwQB6Zj+OnIwiaCOmQC0 MOsRKUJUCp50BHRgUum3ogXnNPEcPPO9C1iCaOuUFBWXlEhaHWxAKvuDmZahUVCu2o7o ChVw== X-Gm-Message-State: AOAM532ghfvSZht7QUXRxtff51OwWAt4FmfRyslBIPJRgjdUQqtPvKWf /5wfTX/Un2BhFa+t/e9nPC+JPN5kin7oj2XhWu2AVA== X-Google-Smtp-Source: ABdhPJxqsgOYMphrGnlqeopcdyeZuhG09nqgCBjA0tgpuWz/pWbsL8jFOVPTPC+0tjRn5eB1bXUqxw5bpkXfV4hIT6A= X-Received: by 2002:ad4:552b:: with SMTP id ba11mr6780194qvb.145.1592531868596; Thu, 18 Jun 2020 18:57:48 -0700 (PDT) MIME-Version: 1.0 References: <20200526105811.30784-1-stevensd@chromium.org> <20200526105811.30784-2-stevensd@chromium.org> <20200604145620-mutt-send-email-mst@kernel.org> <20200618122856.GC4189@ubuntu> In-Reply-To: <20200618122856.GC4189@ubuntu> From: David Stevens Date: Fri, 19 Jun 2020 10:57:37 +0900 Message-ID: Subject: Re: [PATCH v4 1/3] virtio: add dma-buf support for exported objects To: Guennadi Liakhovetski Cc: "Michael S. Tsirkin" , ML dri-devel , virtio-dev@lists.oasis-open.org, Thomas Zimmermann , David Airlie , Maarten Lankhorst , open list , Maxime Ripard , "open list:VIRTIO GPU DRIVER" , "moderated list:DMA BUFFER SHARING FRAMEWORK" , Daniel Vetter , Sumit Semwal , Linux Media Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Thu, Jun 18, 2020 at 9:29 PM Guennadi Liakhovetski wrote: > > Hi Michael, > > On Thu, Jun 04, 2020 at 03:05:23PM -0400, Michael S. Tsirkin wrote: > > On Tue, May 26, 2020 at 07:58:09PM +0900, David Stevens wrote: > > > This change adds a new flavor of dma-bufs that can be used by virtio > > > drivers to share exported objects. A virtio dma-buf can be queried by > > > virtio drivers to obtain the UUID which identifies the underlying > > > exported object. > > > > > > Signed-off-by: David Stevens > > > > Is this just for graphics? If yes I'd rather we put it in the graphics > > driver. We can always move it later ... > > Wouldn't this be the API that audio virtualisation will have to use to share > buffers between the host and any guests? The new flavor of dma-buf isn't directly related to sharing buffers between the host and the guest. The purpose of this API is to help share buffers between multiple virtio devices - e.g. share buffers created by a virito-gpu device with a virito-video device. In particular, the new flavor of dma-buf provides a mechanism to attach identifying metadata to a dma-buf object that is shared between different virtio drivers in a single guest. This identifying metadata can then be passed to the importing device and used to fetch some resource from the exporting device. But the new flavor of dma-buf is an abstraction within the guest kernel, independent of the host-guest boundary, and it's definitely not necessary if we're only talking about a single virtio subsystem. -David > Thanks > Guennadi > > > > --- > > > drivers/virtio/Makefile | 2 +- > > > drivers/virtio/virtio.c | 6 +++ > > > drivers/virtio/virtio_dma_buf.c | 89 +++++++++++++++++++++++++++++++++ > > > include/linux/virtio.h | 1 + > > > include/linux/virtio_dma_buf.h | 58 +++++++++++++++++++++ > > > 5 files changed, 155 insertions(+), 1 deletion(-) > > > create mode 100644 drivers/virtio/virtio_dma_buf.c > > > create mode 100644 include/linux/virtio_dma_buf.h > > > > > > diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile > > > index 29a1386ecc03..ecdae5b596de 100644 > > > --- a/drivers/virtio/Makefile > > > +++ b/drivers/virtio/Makefile > > > @@ -1,5 +1,5 @@ > > > # SPDX-License-Identifier: GPL-2.0 > > > -obj-$(CONFIG_VIRTIO) += virtio.o virtio_ring.o > > > +obj-$(CONFIG_VIRTIO) += virtio.o virtio_ring.o virtio_dma_buf.o > > > obj-$(CONFIG_VIRTIO_MMIO) += virtio_mmio.o > > > obj-$(CONFIG_VIRTIO_PCI) += virtio_pci.o > > > virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o > > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > > > index a977e32a88f2..5d46f0ded92d 100644 > > > --- a/drivers/virtio/virtio.c > > > +++ b/drivers/virtio/virtio.c > > > @@ -357,6 +357,12 @@ int register_virtio_device(struct virtio_device *dev) > > > } > > > EXPORT_SYMBOL_GPL(register_virtio_device); > > > > > > +bool is_virtio_device(struct device *dev) > > > +{ > > > + return dev->bus == &virtio_bus; > > > +} > > > +EXPORT_SYMBOL_GPL(is_virtio_device); > > > + > > > void unregister_virtio_device(struct virtio_device *dev) > > > { > > > int index = dev->index; /* save for after device release */ > > > diff --git a/drivers/virtio/virtio_dma_buf.c b/drivers/virtio/virtio_dma_buf.c > > > new file mode 100644 > > > index 000000000000..23e3399b11ed > > > --- /dev/null > > > +++ b/drivers/virtio/virtio_dma_buf.c > > > @@ -0,0 +1,89 @@ > > > +// SPDX-License-Identifier: GPL-2.0-or-later > > > +/* > > > + * dma-bufs for virtio exported objects > > > + * > > > + * Copyright (C) 2020 Google, Inc. > > > + */ > > > + > > > +#include > > > + > > > +/** > > > + * virtio_dma_buf_export - Creates a new dma-buf for a virtio exported object > > > + * > > > + * This wraps dma_buf_export() to allow virtio drivers to create a dma-buf > > > + * for an virtio exported object that can be queried by other virtio drivers > > > + * for the object's UUID. > > > + */ > > > +struct dma_buf *virtio_dma_buf_export( > > > + const struct virtio_dma_buf_export_info *virtio_exp_info) > > > +{ > > > + struct dma_buf_export_info exp_info; > > > + > > > + if (!virtio_exp_info->ops > > > + || virtio_exp_info->ops->ops.attach != &virtio_dma_buf_attach > > > + || !virtio_exp_info->ops->get_uuid) { > > > + return ERR_PTR(-EINVAL); > > > + } > > > + > > > + exp_info.exp_name = virtio_exp_info->exp_name; > > > + exp_info.owner = virtio_exp_info->owner; > > > + exp_info.ops = &virtio_exp_info->ops->ops; > > > + exp_info.size = virtio_exp_info->size; > > > + exp_info.flags = virtio_exp_info->flags; > > > + exp_info.resv = virtio_exp_info->resv; > > > + exp_info.priv = virtio_exp_info->priv; > > > + BUILD_BUG_ON(sizeof(struct virtio_dma_buf_export_info) > > > + != sizeof(struct dma_buf_export_info)); > > > > This is the only part that gives me pause. Why do we need this hack? > > What's wrong with just using dma_buf_export_info directly, > > and if you want the virtio ops, just using container_off? > > > > > > > > > + > > > + return dma_buf_export(&exp_info); > > > +} > > > +EXPORT_SYMBOL(virtio_dma_buf_export); > > > + > > > +/** > > > + * virtio_dma_buf_attach - mandatory attach callback for virtio dma-bufs > > > + */ > > > +int virtio_dma_buf_attach(struct dma_buf *dma_buf, > > > + struct dma_buf_attachment *attach) > > > +{ > > > + int ret; > > > + const struct virtio_dma_buf_ops *ops = container_of( > > > + dma_buf->ops, const struct virtio_dma_buf_ops, ops); > > > + > > > + if (ops->device_attach) { > > > + ret = ops->device_attach(dma_buf, attach); > > > + if (ret) > > > + return ret; > > > + } > > > + return 0; > > > +} > > > +EXPORT_SYMBOL(virtio_dma_buf_attach); > > > + > > > +/** > > > + * is_virtio_dma_buf - returns true if the given dma-buf is a virtio dma-buf > > > + * @dma_buf: buffer to query > > > + */ > > > +bool is_virtio_dma_buf(struct dma_buf *dma_buf) > > > +{ > > > + return dma_buf->ops->attach == &virtio_dma_buf_attach; > > > +} > > > +EXPORT_SYMBOL(is_virtio_dma_buf); > > > + > > > +/** > > > + * virtio_dma_buf_get_uuid - gets the uuid of the virtio dma-buf's exported object > > > + * @dma_buf: [in] buffer to query > > > + * @uuid: [out] the uuid > > > + * > > > + * Returns: 0 on success, negative on failure. > > > + */ > > > +int virtio_dma_buf_get_uuid(struct dma_buf *dma_buf, > > > + uuid_t *uuid) > > > +{ > > > + const struct virtio_dma_buf_ops *ops = container_of( > > > + dma_buf->ops, const struct virtio_dma_buf_ops, ops); > > > + > > > + if (!is_virtio_dma_buf(dma_buf)) > > > + return -EINVAL; > > > + > > > + return ops->get_uuid(dma_buf, uuid); > > > +} > > > +EXPORT_SYMBOL(virtio_dma_buf_get_uuid); > > > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > > > index 15f906e4a748..9397e25616c4 100644 > > > --- a/include/linux/virtio.h > > > +++ b/include/linux/virtio.h > > > @@ -128,6 +128,7 @@ static inline struct virtio_device *dev_to_virtio(struct device *_dev) > > > void virtio_add_status(struct virtio_device *dev, unsigned int status); > > > int register_virtio_device(struct virtio_device *dev); > > > void unregister_virtio_device(struct virtio_device *dev); > > > +bool is_virtio_device(struct device *dev); > > > > > > void virtio_break_device(struct virtio_device *dev); > > > > > > diff --git a/include/linux/virtio_dma_buf.h b/include/linux/virtio_dma_buf.h > > > new file mode 100644 > > > index 000000000000..29fee167afbd > > > --- /dev/null > > > +++ b/include/linux/virtio_dma_buf.h > > > @@ -0,0 +1,58 @@ > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > +/* > > > + * dma-bufs for virtio exported objects > > > + * > > > + * Copyright (C) 2020 Google, Inc. > > > + */ > > > + > > > +#ifndef _LINUX_VIRTIO_DMA_BUF_H > > > +#define _LINUX_VIRTIO_DMA_BUF_H > > > + > > > +#include > > > +#include > > > +#include > > > + > > > +/** > > > + * struct virtio_dma_buf_ops - operations possible on exported object dma-buf > > > + * @ops: the base dma_buf_ops. ops.attach MUST be virtio_dma_buf_attach. > > > + * @device_attach: [optional] callback invoked by virtio_dma_buf_attach during > > > + * all attach operations. > > > + * @get_uid: [required] callback to get the uuid of the exported object. > > > + */ > > > +struct virtio_dma_buf_ops { > > > + struct dma_buf_ops ops; > > > + int (*device_attach)(struct dma_buf *dma_buf, > > > + struct dma_buf_attachment *attach); > > > + int (*get_uuid)(struct dma_buf *dma_buf, uuid_t *uuid); > > > +}; > > > + > > > +/** > > > + * struct virtio_dma_buf_export_info - see struct dma_buf_export_info > > > + */ > > > +struct virtio_dma_buf_export_info { > > > + const char *exp_name; > > > + struct module *owner; > > > + const struct virtio_dma_buf_ops *ops; > > > + size_t size; > > > + int flags; > > > + struct dma_resv *resv; > > > + void *priv; > > > +}; > > > + > > > +/** > > > + * DEFINE_VIRTIO_DMA_BUF_EXPORT_INFO - helper macro for exporters > > > + */ > > > +#define DEFINE_VIRTIO_DMA_BUF_EXPORT_INFO(name) \ > > > + struct virtio_dma_buf_export_info name = { \ > > > + .exp_name = KBUILD_MODNAME, \ > > > + .owner = THIS_MODULE } > > > + > > > +int virtio_dma_buf_attach(struct dma_buf *dma_buf, > > > + struct dma_buf_attachment *attach); > > > + > > > +struct dma_buf *virtio_dma_buf_export( > > > + const struct virtio_dma_buf_export_info *virtio_exp_info); > > > +bool is_virtio_dma_buf(struct dma_buf *dma_buf); > > > +int virtio_dma_buf_get_uuid(struct dma_buf *dma_buf, uuid_t *uuid); > > > + > > > +#endif /* _LINUX_VIRTIO_DMA_BUF_H */ > > > -- > > > 2.27.0.rc0.183.gde8f92d652-goog > > > > _______________________________________________ > > Virtualization mailing list > > Virtualization@lists.linux-foundation.org > > https://lists.linuxfoundation.org/mailman/listinfo/virtualization