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SubjectRe: [PATCH 1/2] vfio powerpc: implemented IOMMU driver for VFIO
On 27/11/12 05:20, Alex Williamson wrote:
> On Fri, 2012-11-23 at 20:03 +1100, Alexey Kardashevskiy wrote:
>> VFIO implements platform independent stuff such as
>> a PCI driver, BAR access (via read/write on a file descriptor
>> or direct mapping when possible) and IRQ signaling.
>>
>> The platform dependent part includes IOMMU initialization
>> and handling. This patch implements an IOMMU driver for VFIO
>> which does mapping/unmapping pages for the guest IO and
>> provides information about DMA window (required by a POWERPC
>> guest).
>>
>> The counterpart in QEMU is required to support this functionality.
>>
>> Cc: David Gibson <david@gibson.dropbear.id.au>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>> drivers/vfio/Kconfig | 6 +
>> drivers/vfio/Makefile | 1 +
>> drivers/vfio/vfio_iommu_spapr_tce.c | 247 +++++++++++++++++++++++++++++++++++
>> include/linux/vfio.h | 20 +++
>> 4 files changed, 274 insertions(+)
>> create mode 100644 drivers/vfio/vfio_iommu_spapr_tce.c
>>
>> diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
>> index 7cd5dec..b464687 100644
>> --- a/drivers/vfio/Kconfig
>> +++ b/drivers/vfio/Kconfig
>> @@ -3,10 +3,16 @@ config VFIO_IOMMU_TYPE1
>> depends on VFIO
>> default n
>>
>> +config VFIO_IOMMU_SPAPR_TCE
>> + tristate
>> + depends on VFIO && SPAPR_TCE_IOMMU
>> + default n
>> +
>> menuconfig VFIO
>> tristate "VFIO Non-Privileged userspace driver framework"
>> depends on IOMMU_API
>> select VFIO_IOMMU_TYPE1 if X86
>> + select VFIO_IOMMU_SPAPR_TCE if PPC_POWERNV
>> help
>> VFIO provides a framework for secure userspace device drivers.
>> See Documentation/vfio.txt for more details.
>> diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
>> index 2398d4a..72bfabc 100644
>> --- a/drivers/vfio/Makefile
>> +++ b/drivers/vfio/Makefile
>> @@ -1,3 +1,4 @@
>> obj-$(CONFIG_VFIO) += vfio.o
>> obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o
>> +obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
>> obj-$(CONFIG_VFIO_PCI) += pci/
>> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
>> new file mode 100644
>> index 0000000..46a6298
>> --- /dev/null
>> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
>> @@ -0,0 +1,247 @@
>> +/*
>> + * VFIO: IOMMU DMA mapping support for TCE on POWER
>> + *
>> + * Copyright (C) 2012 IBM Corp. All rights reserved.
>> + * Author: Alexey Kardashevskiy <aik@ozlabs.ru>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * Derived from original vfio_iommu_type1.c:
>> + * Copyright (C) 2012 Red Hat, Inc. All rights reserved.
>> + * Author: Alex Williamson <alex.williamson@redhat.com>
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/pci.h>
>> +#include <linux/slab.h>
>> +#include <linux/uaccess.h>
>> +#include <linux/err.h>
>> +#include <linux/vfio.h>
>> +#include <asm/iommu.h>
>> +
>> +#define DRIVER_VERSION "0.1"
>> +#define DRIVER_AUTHOR "aik@ozlabs.ru"
>> +#define DRIVER_DESC "VFIO IOMMU SPAPR TCE"
>> +
>> +static void tce_iommu_detach_group(void *iommu_data,
>> + struct iommu_group *iommu_group);
>> +
>> +/*
>> + * VFIO IOMMU fd for SPAPR_TCE IOMMU implementation
>> + */
>> +
>> +/*
>> + * The container descriptor supports only a single group per container.
>> + * Required by the API as the container is not supplied with the IOMMU group
>> + * at the moment of initialization.
>> + */
>> +struct tce_container {
>> + struct mutex lock;
>> + struct iommu_table *tbl;
>> +};
>> +
>> +static void *tce_iommu_open(unsigned long arg)
>> +{
>> + struct tce_container *container;
>> +
>> + if (arg != VFIO_SPAPR_TCE_IOMMU) {
>> + printk(KERN_ERR "tce_vfio: Wrong IOMMU type\n");
>> + return ERR_PTR(-EINVAL);
>> + }
>> +
>> + container = kzalloc(sizeof(*container), GFP_KERNEL);
>> + if (!container)
>> + return ERR_PTR(-ENOMEM);
>> +
>> + mutex_init(&container->lock);
>> +
>> + return container;
>> +}
>> +
>> +static void tce_iommu_release(void *iommu_data)
>> +{
>> + struct tce_container *container = iommu_data;
>> +
>> + WARN_ON(container->tbl && !container->tbl->it_group);
>
> I think your patch ordering is backwards here. it_group isn't added
> until 2/2. I'd really like to see the arch/powerpc code approved and
> merged by the powerpc maintainer before we add the code that makes use
> of it into vfio. Otherwise we just get lots of churn if interfaces
> change or they disapprove of it altogether.


Makes sense, thanks.


>> + if (container->tbl && container->tbl->it_group)
>> + tce_iommu_detach_group(iommu_data, container->tbl->it_group);
>> +
>> + mutex_destroy(&container->lock);
>> +
>> + kfree(container);
>> +}
>> +
>> +static long tce_iommu_ioctl(void *iommu_data,
>> + unsigned int cmd, unsigned long arg)
>> +{
>> + struct tce_container *container = iommu_data;
>> + unsigned long minsz;
>> +
>> + switch (cmd) {
>> + case VFIO_CHECK_EXTENSION: {
>> + return (arg == VFIO_SPAPR_TCE_IOMMU) ? 1 : 0;
>> + }
>> + case VFIO_IOMMU_SPAPR_TCE_GET_INFO: {
>> + struct vfio_iommu_spapr_tce_info info;
>> + struct iommu_table *tbl = container->tbl;
>> +
>> + if (WARN_ON(!tbl))
>> + return -ENXIO;
>> +
>> + minsz = offsetofend(struct vfio_iommu_spapr_tce_info,
>> + dma64_window_size);
>> +
>> + if (copy_from_user(&info, (void __user *)arg, minsz))
>> + return -EFAULT;
>> +
>> + if (info.argsz < minsz)
>> + return -EINVAL;
>> +
>> + info.dma32_window_start = tbl->it_offset << IOMMU_PAGE_SHIFT;
>> + info.dma32_window_size = tbl->it_size << IOMMU_PAGE_SHIFT;
>> + info.dma64_window_start = 0;
>> + info.dma64_window_size = 0;
>> + info.flags = 0;
>> +
>> + if (copy_to_user((void __user *)arg, &info, minsz))
>> + return -EFAULT;
>> +
>> + return 0;
>> + }
>> + case VFIO_IOMMU_MAP_DMA: {
>> + vfio_iommu_spapr_tce_dma_map param;
>> + struct iommu_table *tbl = container->tbl;
>> + enum dma_data_direction direction = DMA_NONE;
>> +
>> + if (WARN_ON(!tbl))
>> + return -ENXIO;
>> +
>> + minsz = offsetofend(vfio_iommu_spapr_tce_dma_map, size);
>> +
>> + if (copy_from_user(&param, (void __user *)arg, minsz))
>> + return -EFAULT;
>> +
>> + if (param.argsz < minsz)
>> + return -EINVAL;
>> +
>> + if ((param.flags & VFIO_DMA_MAP_FLAG_READ) &&
>> + (param.flags & VFIO_DMA_MAP_FLAG_WRITE)) {
>> + direction = DMA_BIDIRECTIONAL;
>> + } else if (param.flags & VFIO_DMA_MAP_FLAG_READ) {
>> + direction = DMA_TO_DEVICE;
>> + } else if (param.flags & VFIO_DMA_MAP_FLAG_WRITE) {
>> + direction = DMA_FROM_DEVICE;
>> + }
>> +
>> + param.size += param.iova & ~IOMMU_PAGE_MASK;
>> + param.size = _ALIGN_UP(param.size, IOMMU_PAGE_SIZE);
>
> On x86 we force iova, vaddr, and size to all be aligned to the smallest
> page granularity of the iommu and return -EINVAL if it doesn't fit.
> What does it imply to the user if they're always aligned to work here?
> Won't this interface happily map overlapping entries with no indication
> to the user that the previous mapping is no longer valid?
> Maybe another reason why a combined unmap/map makes me nervous, we have
> to assume the user knows what they're doing.


I got used to guests which do know what they are doing so I am pretty calm :)
but ok, I'll move alignment to the QEMU, it makes sense.


>> +
>> + return iommu_put_tces(tbl, param.iova >> IOMMU_PAGE_SHIFT,
>> + param.vaddr & IOMMU_PAGE_MASK, direction,
>> + param.size >> IOMMU_PAGE_SHIFT);
>> + }
>> + case VFIO_IOMMU_UNMAP_DMA: {
>> + vfio_iommu_spapr_tce_dma_unmap param;
>> + struct iommu_table *tbl = container->tbl;
>> +
>> + if (WARN_ON(!tbl))
>> + return -ENXIO;
>> +
>> + minsz = offsetofend(vfio_iommu_spapr_tce_dma_unmap, size);
>> +
>> + if (copy_from_user(&param, (void __user *)arg, minsz))
>> + return -EFAULT;
>> +
>> + if (param.argsz < minsz)
>> + return -EINVAL;
>> +
>> + param.size += param.iova & ~IOMMU_PAGE_MASK;
>> + param.size = _ALIGN_UP(param.size, IOMMU_PAGE_SIZE);
>> +
>> + return iommu_put_tces(tbl, param.iova >> IOMMU_PAGE_SHIFT,
>> + 0, DMA_NONE, param.size >> IOMMU_PAGE_SHIFT);
>> + }
>> + default:
>> + printk(KERN_WARNING "tce_vfio: unexpected cmd %x\n", cmd);
>
> pr_warn
>
>> + }
>> +
>> + return -ENOTTY;
>> +}
>> +
>> +static int tce_iommu_attach_group(void *iommu_data,
>> + struct iommu_group *iommu_group)
>> +{
>> + struct tce_container *container = iommu_data;
>> + struct iommu_table *tbl = iommu_group_get_iommudata(iommu_group);
>> +
>> + BUG_ON(!tbl);
>> + mutex_lock(&container->lock);
>> + pr_debug("tce_vfio: Attaching group #%u to iommu %p\n",
>> + iommu_group_id(iommu_group), iommu_group);
>> + if (container->tbl) {
>> + printk(KERN_WARNING "tce_vfio: Only one group per IOMMU container is allowed, existing id=%d, attaching id=%d\n",
>
> pr_warn
>
>> + iommu_group_id(container->tbl->it_group),
>> + iommu_group_id(iommu_group));
>> + mutex_unlock(&container->lock);
>> + return -EBUSY;
>> + }
>> +
>> + container->tbl = tbl;
>
> Would it be too much paranoia to clear all the tce here as you do below
> on detach?

Guess so. I do unmap on detach() and the guest calls put_tce(0) (i.e.
unmaps) the whole DMA window at the boot time.


> ie. is there any risk that there's leftover programming?
> x86 allocates a new domain on open of the iommu, so we always start out
> clean.


>> + mutex_unlock(&container->lock);
>> +
>> + return 0;
>> +}
>> +
>> +static void tce_iommu_detach_group(void *iommu_data,
>> + struct iommu_group *iommu_group)
>> +{
>> + struct tce_container *container = iommu_data;
>> + struct iommu_table *tbl = iommu_group_get_iommudata(iommu_group);
>> +
>> + BUG_ON(!tbl);
>> + mutex_lock(&container->lock);
>> + if (tbl != container->tbl) {
>> + printk(KERN_WARNING "tce_vfio: detaching group #%u, expected group is #%u\n",
>
> pr_warn
>
>> + iommu_group_id(iommu_group),
>> + iommu_group_id(tbl->it_group));
>> + } else {
>> +
>> + pr_debug("tce_vfio: detaching group #%u from iommu %p\n",
>> + iommu_group_id(iommu_group), iommu_group);
>> +
>> + iommu_put_tces(tbl, tbl->it_offset, 0, DMA_NONE, tbl->it_size);
>
> So this cleans out any mappings when vfio is closed, good.
>
>> + container->tbl = NULL;
>> + }
>> + mutex_unlock(&container->lock);
>> +}
>> +
>> +const struct vfio_iommu_driver_ops tce_iommu_driver_ops = {
>> + .name = "iommu-vfio-powerpc",
>> + .owner = THIS_MODULE,
>> + .open = tce_iommu_open,
>> + .release = tce_iommu_release,
>> + .ioctl = tce_iommu_ioctl,
>> + .attach_group = tce_iommu_attach_group,
>> + .detach_group = tce_iommu_detach_group,
>> +};
>> +
>> +static int __init tce_iommu_init(void)
>> +{
>> + return vfio_register_iommu_driver(&tce_iommu_driver_ops);
>> +}
>> +
>> +static void __exit tce_iommu_cleanup(void)
>> +{
>> + vfio_unregister_iommu_driver(&tce_iommu_driver_ops);
>> +}
>> +
>> +module_init(tce_iommu_init);
>> +module_exit(tce_iommu_cleanup);
>> +
>> +MODULE_VERSION(DRIVER_VERSION);
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_AUTHOR(DRIVER_AUTHOR);
>> +MODULE_DESCRIPTION(DRIVER_DESC);
>> +
>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>> index 0a4f180..3ecd65c 100644
>> --- a/include/linux/vfio.h
>> +++ b/include/linux/vfio.h
>> @@ -99,6 +99,7 @@ extern void vfio_unregister_iommu_driver(
>> /* Extensions */
>>
>> #define VFIO_TYPE1_IOMMU 1
>> +#define VFIO_SPAPR_TCE_IOMMU 2
>>
>> /*
>> * The IOCTL interface is designed for extensibility by embedding the
>> @@ -442,4 +443,23 @@ struct vfio_iommu_type1_dma_unmap {
>>
>> #define VFIO_IOMMU_UNMAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 14)
>>
>> +/* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU -------- */
>> +
>> +struct vfio_iommu_spapr_tce_info {
>> + __u32 argsz;
>> + __u32 flags;
>> + __u32 dma32_window_start;
>> + __u32 dma32_window_size;
>> + __u64 dma64_window_start;
>> + __u64 dma64_window_size;
>> +};
>
> Is there anything we can document about this?

I'll put some.

> It should probably list that size is in bytes. Is there any need to communicate the IOMMU page
> size here?

It is always 4k. I'll put it to comments.

>> +
>> +#define VFIO_IOMMU_SPAPR_TCE_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
>> +
>> +/* Reuse type1 map/unmap structs as they are the same at the moment */
>> +typedef struct vfio_iommu_type1_dma_map vfio_iommu_spapr_tce_dma_map;
>> +typedef struct vfio_iommu_type1_dma_unmap vfio_iommu_spapr_tce_dma_unmap;
>> +
>> +/* ***************************************************************** */
>> +
>> #endif /* VFIO_H */
>
> Thanks,
>
> Alex
>
>
>


--
Alexey


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