| Message ID | 1653944417-17168-7-git-send-email-olekstysh@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | virtio: Solution to restrict memory access under Xen using xen-grant DMA-mapping layer | expand |
On Tue, 31 May 2022, Oleksandr Tyshchenko wrote: > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> > > 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> > --- > According to the discussion at: > https://lore.kernel.org/xen-devel/c0f78aab-e723-fe00-a310-9fe52ec75e48@gmail.com/ > > Change V2 -> V3: > - new patch > --- > drivers/xen/Kconfig | 4 +++ > drivers/xen/Makefile | 1 + > drivers/xen/grant-dma-iommu.c | 78 +++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 83 insertions(+) > create mode 100644 drivers/xen/grant-dma-iommu.c > > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig > index a7bd8ce..35d20d9 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 1a23cb0..c0503f1 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 00000000..16b8bc0 > --- /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); > -- > 2.7.4 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index a7bd8ce..35d20d9 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 1a23cb0..c0503f1 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 00000000..16b8bc0 --- /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);