[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH V3 7/8] xen/grant-dma-ops: Retrieve the ID of backend's domain for DT devices
On Tue, 31 May 2022, Oleksandr Tyshchenko wrote: > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> > > Use the presence of "iommus" property pointed to the IOMMU node with > recently introduced "xen,grant-dma" compatible as a clear indicator > of enabling Xen grant mappings scheme for that device and read the ID > of Xen domain where the corresponding backend is running. The domid > (domain ID) is used as an argument to the Xen grant mapping APIs. > > To avoid the deferred probe timeout which takes place after reusing > generic IOMMU device tree bindings (because the IOMMU device never > becomes available) enable recently introduced stub IOMMU driver by > selecting XEN_GRANT_DMA_IOMMU. > > Also introduce xen_is_grant_dma_device() to check whether xen-grant > DMA ops need to be set for a passed device. > > Remove the hardcoded domid 0 in xen_grant_setup_dma_ops(). > > Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> > --- > Changes RFC -> V1: > - new patch, split required changes from commit: > "[PATCH 4/6] virtio: Various updates to xen-virtio DMA ops layer" > - update checks in xen_virtio_setup_dma_ops() to only support > DT devices for now > - remove the "virtio,mmio" check from xen_is_virtio_device() > - remane everything according to the new naming scheme: > s/virtio/grant_dma > > Changes V1 -> V2: > - remove dev_is_pci() check in xen_grant_setup_dma_ops() > - remove EXPORT_SYMBOL_GPL(xen_is_grant_dma_device); > > Changes V2 -> V3: > - Stefano already gave his Reviewed-by, I dropped it due to the changes > (significant) > - update commit description > - reuse generic IOMMU device tree bindings, select XEN_GRANT_DMA_IOMMU > to avoid the deferred probe timeout > --- > drivers/xen/Kconfig | 1 + > drivers/xen/grant-dma-ops.c | 48 > ++++++++++++++++++++++++++++++++++++++------- > include/xen/xen-ops.h | 5 +++++ > 3 files changed, 47 insertions(+), 7 deletions(-) > > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig > index 35d20d9..bfd5f4f 100644 > --- a/drivers/xen/Kconfig > +++ b/drivers/xen/Kconfig > @@ -347,6 +347,7 @@ config XEN_VIRTIO > bool "Xen virtio support" > depends on VIRTIO > select XEN_GRANT_DMA_OPS > + select XEN_GRANT_DMA_IOMMU if OF > help > Enable virtio support for running as Xen guest. Depending on the > guest type this will require special support on the backend side > diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c > index 44659f4..6586152 100644 > --- a/drivers/xen/grant-dma-ops.c > +++ b/drivers/xen/grant-dma-ops.c > @@ -55,11 +55,6 @@ static struct xen_grant_dma_data > *find_xen_grant_dma_data(struct device *dev) > * Such a DMA address is formed by using the grant reference as a frame > * number and setting the highest address bit (this bit is for the backend > * to be able to distinguish it from e.g. a mmio address). > - * > - * Note that for now we hard wire dom0 to be the backend domain. In order > - * to support any domain as backend we'd need to add a way to communicate > - * the domid of this backend, e.g. via Xenstore, via the PCI-device's > - * config space or DT/ACPI. > */ > static void *xen_grant_dma_alloc(struct device *dev, size_t size, > dma_addr_t *dma_handle, gfp_t gfp, > @@ -275,9 +270,26 @@ static const struct dma_map_ops xen_grant_dma_ops = { > .dma_supported = xen_grant_dma_supported, > }; > > +bool xen_is_grant_dma_device(struct device *dev) > +{ > + struct device_node *iommu_np; > + bool has_iommu; > + > + /* XXX Handle only DT devices for now */ > + if (!dev->of_node) > + return false; > + > + 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); > + > + return has_iommu; > +} > + > void xen_grant_setup_dma_ops(struct device *dev) > { > struct xen_grant_dma_data *data; > + struct of_phandle_args iommu_spec; > > data = find_xen_grant_dma_data(dev); > if (data) { > @@ -285,12 +297,34 @@ void xen_grant_setup_dma_ops(struct device *dev) > return; > } > > + /* XXX ACPI device unsupported for now */ > + if (!dev->of_node) > + goto err; > + > + if (of_parse_phandle_with_args(dev->of_node, "iommus", "#iommu-cells", > + 0, &iommu_spec)) { > + dev_err(dev, "Cannot parse iommus property\n"); > + goto err; > + } > + > + if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") || > + iommu_spec.args_count != 1) { > + dev_err(dev, "Incompatible IOMMU node\n"); > + of_node_put(iommu_spec.np); > + goto err; > + } > + > + of_node_put(iommu_spec.np); > + > data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); > if (!data) > goto err; > > - /* XXX The dom0 is hardcoded as the backend domain for now */ > - data->backend_domid = 0; > + /* > + * The endpoint ID here means the ID of the domain where the > corresponding > + * backend is running > + */ > + data->backend_domid = iommu_spec.args[0]; > > if (xa_err(xa_store(&xen_grant_dma_devices, (unsigned long)dev, data, > GFP_KERNEL))) { > diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h > index 4f9fad5..62be9dc 100644 > --- a/include/xen/xen-ops.h > +++ b/include/xen/xen-ops.h > @@ -223,10 +223,15 @@ static inline void xen_preemptible_hcall_end(void) { } > > #ifdef CONFIG_XEN_GRANT_DMA_OPS > void xen_grant_setup_dma_ops(struct device *dev); > +bool xen_is_grant_dma_device(struct device *dev); > #else > static inline void xen_grant_setup_dma_ops(struct device *dev) > { > } > +static inline bool xen_is_grant_dma_device(struct device *dev) > +{ > + return false; > +} > #endif /* CONFIG_XEN_GRANT_DMA_OPS */ > > #endif /* INCLUDE_XEN_OPS_H */ > -- > 2.7.4 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
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