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    SubjectRe: [PATCH V2 6/7] xen/grant-dma-ops: Retrieve the ID of backend's domain for DT devices
    On Sat, 7 May 2022, Oleksandr Tyshchenko wrote:
    > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
    >
    > Use the presence of recently introduced "xen,dev-domid" property
    > in the device node as a clear indicator of enabling Xen grant
    > mappings scheme for that device and read the ID of Xen domain where
    > the corresponding backend resides. The ID (domid) is used as
    > an argument to the Xen grant mapping APIs.
    >
    > 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@epam.com>

    Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


    > ---
    > 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);
    > ---
    > drivers/xen/grant-dma-ops.c | 24 +++++++++++++++++-------
    > include/xen/xen-ops.h | 5 +++++
    > 2 files changed, 22 insertions(+), 7 deletions(-)
    >
    > diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
    > index 29ad7bf..8924178 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,
    > @@ -275,6 +270,15 @@ 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)
    > +{
    > + /* XXX Handle only DT devices for now */
    > + if (!dev->of_node)
    > + return false;
    > +
    > + return of_property_read_bool(dev->of_node, "xen,dev-domid");
    > +}
    > +
    > void xen_grant_setup_dma_ops(struct device *dev)
    > {
    > struct xen_grant_dma_data *data;
    > @@ -286,8 +290,14 @@ void xen_grant_setup_dma_ops(struct device *dev)
    > return;
    > }
    >
    > - /* XXX The dom0 is hardcoded as the backend domain for now */
    > - dev_domid = 0;
    > + /* XXX ACPI device unsupported for now */
    > + if (!dev->of_node)
    > + goto err;
    > +
    > + if (of_property_read_u32(dev->of_node, "xen,dev-domid", &dev_domid)) {
    > + dev_err(dev, "xen,dev-domid property is not present\n");
    > + goto err;
    > + }
    >
    > data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
    > if (!data)
    > 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@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
    >

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