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author | Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> | 2022-06-02 22:23:51 +0300 |
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committer | Juergen Gross <jgross@suse.com> | 2022-06-06 16:07:30 +0200 |
commit | 1ca55d50e50c74747a7b8846dac306fbe5ac4cf5 (patch) | |
tree | b65bbd049e63b1bb0cd6850586c2b63e8521e3ca /drivers/xen | |
parent | add413a1d966d8458571a2571881903d234a9f8e (diff) | |
download | linux-1ca55d50e50c74747a7b8846dac306fbe5ac4cf5.tar.bz2 |
xen/grant-dma-iommu: Introduce stub IOMMU driver
In order to reuse generic IOMMU device tree bindings by Xen grant
DMA-mapping layer we need to add this stub driver from a fw_devlink
perspective (grant-dma-ops cannot be converted into the proper
IOMMU driver).
Otherwise, just reusing IOMMU bindings (without having a corresponding
driver) leads to the deferred probe timeout afterwards, because
the IOMMU device never becomes available.
This stub driver does nothing except registering empty iommu_ops,
the upper layer "of_iommu" will treat this as NO_IOMMU condition
and won't return -EPROBE_DEFER.
As this driver is quite different from the most hardware IOMMU
implementations and only needed in Xen guests, place it in drivers/xen
directory. The subsequent commit will make use of it.
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1654197833-25362-7-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'drivers/xen')
-rw-r--r-- | drivers/xen/Kconfig | 4 | ||||
-rw-r--r-- | drivers/xen/Makefile | 1 | ||||
-rw-r--r-- | drivers/xen/grant-dma-iommu.c | 78 |
3 files changed, 83 insertions, 0 deletions
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index a7bd8ce7a1d2..35d20d90390b 100644 --- a/drivers/xen/Kconfig +++ b/drivers/xen/Kconfig @@ -335,6 +335,10 @@ config XEN_UNPOPULATED_ALLOC having to balloon out RAM regions in order to obtain physical memory space to create such mappings. +config XEN_GRANT_DMA_IOMMU + bool + select IOMMU_API + config XEN_GRANT_DMA_OPS bool select DMA_OPS diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile index 1a23cb0dc188..c0503f1c7d5b 100644 --- a/drivers/xen/Makefile +++ b/drivers/xen/Makefile @@ -40,3 +40,4 @@ xen-privcmd-y := privcmd.o privcmd-buf.o obj-$(CONFIG_XEN_FRONT_PGDIR_SHBUF) += xen-front-pgdir-shbuf.o obj-$(CONFIG_XEN_UNPOPULATED_ALLOC) += unpopulated-alloc.o obj-$(CONFIG_XEN_GRANT_DMA_OPS) += grant-dma-ops.o +obj-$(CONFIG_XEN_GRANT_DMA_IOMMU) += grant-dma-iommu.o diff --git a/drivers/xen/grant-dma-iommu.c b/drivers/xen/grant-dma-iommu.c new file mode 100644 index 000000000000..16b8bc0c0b33 --- /dev/null +++ b/drivers/xen/grant-dma-iommu.c @@ -0,0 +1,78 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Stub IOMMU driver which does nothing. + * The main purpose of it being present is to reuse generic IOMMU device tree + * bindings by Xen grant DMA-mapping layer. + * + * Copyright (C) 2022 EPAM Systems Inc. + */ + +#include <linux/iommu.h> +#include <linux/of.h> +#include <linux/platform_device.h> + +struct grant_dma_iommu_device { + struct device *dev; + struct iommu_device iommu; +}; + +/* Nothing is really needed here */ +static const struct iommu_ops grant_dma_iommu_ops; + +static const struct of_device_id grant_dma_iommu_of_match[] = { + { .compatible = "xen,grant-dma" }, + { }, +}; + +static int grant_dma_iommu_probe(struct platform_device *pdev) +{ + struct grant_dma_iommu_device *mmu; + int ret; + + mmu = devm_kzalloc(&pdev->dev, sizeof(*mmu), GFP_KERNEL); + if (!mmu) + return -ENOMEM; + + mmu->dev = &pdev->dev; + + ret = iommu_device_register(&mmu->iommu, &grant_dma_iommu_ops, &pdev->dev); + if (ret) + return ret; + + platform_set_drvdata(pdev, mmu); + + return 0; +} + +static int grant_dma_iommu_remove(struct platform_device *pdev) +{ + struct grant_dma_iommu_device *mmu = platform_get_drvdata(pdev); + + platform_set_drvdata(pdev, NULL); + iommu_device_unregister(&mmu->iommu); + + return 0; +} + +static struct platform_driver grant_dma_iommu_driver = { + .driver = { + .name = "grant-dma-iommu", + .of_match_table = grant_dma_iommu_of_match, + }, + .probe = grant_dma_iommu_probe, + .remove = grant_dma_iommu_remove, +}; + +static int __init grant_dma_iommu_init(void) +{ + struct device_node *iommu_np; + + iommu_np = of_find_matching_node(NULL, grant_dma_iommu_of_match); + if (!iommu_np) + return 0; + + of_node_put(iommu_np); + + return platform_driver_register(&grant_dma_iommu_driver); +} +subsys_initcall(grant_dma_iommu_init); |