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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B513C433FE for ; Wed, 19 Oct 2022 00:58:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229862AbiJSA6O (ORCPT ); Tue, 18 Oct 2022 20:58:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35216 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229508AbiJSA6K (ORCPT ); Tue, 18 Oct 2022 20:58:10 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA34BCBFEA for ; Tue, 18 Oct 2022 17:58:06 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 356E5B82189 for ; Wed, 19 Oct 2022 00:58:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 308A6C433D6; Wed, 19 Oct 2022 00:58:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666141084; bh=pnxCyzPm3hjqwJLkvTjMO+xVkN+jfmiHlHruC5BM2xU=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=l8P6dB7L/PRrKCfkvtxwg0woenifQcNqkdaxEJJT12zZg+mgPS102pKwLkZWhtf4O J191jNBUX1ZOYGCmKRSQPOo8HfUlEX0gzeo99VYeDnSnTzxxaExkxia0oEhF7DG6ca Y8Q65n3IINzP58lQknYtLnBABCQi4qoaaLpTNT6nJHGDxSl/RtsSJSDZeAbWTwIMCR O4sRFI2PegWbckVWyqub8rAgqKuSaDoKgmeUtjagtKdyYFaso/aCkBbAsiiuJIo9sw 20c9yLt26Uq8ctE3ko6HMZL/YAoEKa0wR50NKO8VLpMmVWSorKjPMYCyKy2dk+HS9I rxgF34+Hnfrzw== Date: Tue, 18 Oct 2022 17:58:01 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@ubuntu-linux-20-04-desktop To: Oleksandr Tyshchenko cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Oleksandr Tyshchenko , Stefano Stabellini , Juergen Gross Subject: Re: [PATCH V2] xen/virtio: Handle PCI devices which Host controller is described in DT In-Reply-To: <20221015153409.918775-1-olekstysh@gmail.com> Message-ID: References: <20221015153409.918775-1-olekstysh@gmail.com> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 15 Oct 2022, Oleksandr Tyshchenko wrote: > From: Oleksandr Tyshchenko > > Use the same "xen-grant-dma" device concept for the PCI devices > behind device-tree based PCI Host controller, but with one modification. > Unlike for platform devices, we cannot use generic IOMMU bindings > (iommus property), as we need to support more flexible configuration. > The problem is that PCI devices under the single PCI Host controller > may have the backends running in different Xen domains and thus have > different endpoints ID (backend domains ID). > > So use generic PCI-IOMMU bindings instead (iommu-map/iommu-map-mask > properties) which allows us to describe relationship between PCI > devices and backend domains ID properly. > > Signed-off-by: Oleksandr Tyshchenko Now that I understood the approach and the reasons for it, I can review the patch :-) Please add an example of the bindings in the commit message. > --- > Slightly RFC. This is needed to support Xen grant mappings for virtio-pci devices > on Arm at some point in the future. The Xen toolstack side is not completely ready yet. > Here, for PCI devices we use more flexible way to pass backend domid to the guest > than for platform devices. > > Changes V1 -> V2: > - update commit description > - rebase > - rework to use generic PCI-IOMMU bindings instead of generic IOMMU bindings > > Previous discussion is at: > https://lore.kernel.org/xen-devel/20221006174804.2003029-1-olekstysh@gmail.com/ > > Based on: > https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git/log/?h=for-linus-6.1 > --- > drivers/xen/grant-dma-ops.c | 87 ++++++++++++++++++++++++++++++++----- > 1 file changed, 76 insertions(+), 11 deletions(-) > > diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c > index daa525df7bdc..b79d9d6ce154 100644 > --- a/drivers/xen/grant-dma-ops.c > +++ b/drivers/xen/grant-dma-ops.c > @@ -10,6 +10,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -292,12 +293,55 @@ static const struct dma_map_ops xen_grant_dma_ops = { > .dma_supported = xen_grant_dma_supported, > }; > > +static struct device_node *xen_dt_get_pci_host_node(struct device *dev) > +{ > + struct pci_dev *pdev = to_pci_dev(dev); > + struct pci_bus *bus = pdev->bus; > + > + /* Walk up to the root bus to look for PCI Host controller */ > + while (!pci_is_root_bus(bus)) > + bus = bus->parent; > + > + return of_node_get(bus->bridge->parent->of_node); > +} It seems silly that we need to walk the hierachy that way, but I couldn't find another way to do it > +static struct device_node *xen_dt_get_node(struct device *dev) > +{ > + if (dev_is_pci(dev)) > + return xen_dt_get_pci_host_node(dev); > + > + return of_node_get(dev->of_node); > +} > + > +static int xen_dt_map_id(struct device *dev, struct device_node **iommu_np, > + u32 *sid) > +{ > + struct pci_dev *pdev = to_pci_dev(dev); > + u32 rid = PCI_DEVID(pdev->bus->number, pdev->devfn); > + struct device_node *host_np; > + int ret; > + > + host_np = xen_dt_get_pci_host_node(dev); > + if (!host_np) > + return -ENODEV; > + > + ret = of_map_id(host_np, rid, "iommu-map", "iommu-map-mask", iommu_np, sid); > + of_node_put(host_np); > + return ret; > +} > + > static bool xen_is_dt_grant_dma_device(struct device *dev) > { > - struct device_node *iommu_np; > + struct device_node *iommu_np = NULL; > bool has_iommu; > > - iommu_np = of_parse_phandle(dev->of_node, "iommus", 0); > + if (dev_is_pci(dev)) { > + if (xen_dt_map_id(dev, &iommu_np, NULL)) > + return false; > + } else > + iommu_np = of_parse_phandle(dev->of_node, "iommus", 0); > + > has_iommu = iommu_np && > of_device_is_compatible(iommu_np, "xen,grant-dma"); > of_node_put(iommu_np); > @@ -307,9 +351,17 @@ static bool xen_is_dt_grant_dma_device(struct device *dev) > > bool xen_is_grant_dma_device(struct device *dev) > { > + struct device_node *np; > + > /* XXX Handle only DT devices for now */ > - if (dev->of_node) > - return xen_is_dt_grant_dma_device(dev); > + np = xen_dt_get_node(dev); > + if (np) { > + bool ret; > + > + ret = xen_is_dt_grant_dma_device(dev); > + of_node_put(np); > + return ret; > + } We don't need to walk the PCI hierachy twice. Maybe we can add the of_node check directly to xen_is_dt_grant_dma_device? > return false; > } > @@ -325,12 +377,19 @@ bool xen_virtio_mem_acc(struct virtio_device *dev) > static int xen_dt_grant_init_backend_domid(struct device *dev, > struct xen_grant_dma_data *data) > { > - struct of_phandle_args iommu_spec; > + struct of_phandle_args iommu_spec = { .args_count = 1 }; > > - if (of_parse_phandle_with_args(dev->of_node, "iommus", "#iommu-cells", > - 0, &iommu_spec)) { > - dev_err(dev, "Cannot parse iommus property\n"); > - return -ESRCH; > + if (dev_is_pci(dev)) { > + if (xen_dt_map_id(dev, &iommu_spec.np, iommu_spec.args)) { > + dev_err(dev, "Cannot translate ID\n"); > + return -ESRCH; > + } > + } else { > + if (of_parse_phandle_with_args(dev->of_node, "iommus", "#iommu-cells", > + 0, &iommu_spec)) { > + dev_err(dev, "Cannot parse iommus property\n"); > + return -ESRCH; > + } > } > > if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") || > @@ -354,6 +413,7 @@ static int xen_dt_grant_init_backend_domid(struct device *dev, > void xen_grant_setup_dma_ops(struct device *dev) > { > struct xen_grant_dma_data *data; > + struct device_node *np; > > data = find_xen_grant_dma_data(dev); > if (data) { > @@ -365,8 +425,13 @@ void xen_grant_setup_dma_ops(struct device *dev) > if (!data) > goto err; > > - if (dev->of_node) { > - if (xen_dt_grant_init_backend_domid(dev, data)) > + np = xen_dt_get_node(dev); > + if (np) { > + int ret; > + > + ret = xen_dt_grant_init_backend_domid(dev, data); > + of_node_put(np); > + if (ret) > goto err; > } else if (IS_ENABLED(CONFIG_XEN_VIRTIO_FORCE_GRANT)) { > dev_info(dev, "Using dom0 as backend\n"); > -- > 2.25.1 >