Re: [PATCH] vfio powerpc: implemented IOMMU driver for VFIO

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 2012-12-07 at 18:34 +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 |  348 +++++++++++++++++++++++++++++++++++
>  include/linux/vfio.h                |   30 +++
>  4 files changed, 385 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..b0f81fe
> --- /dev/null
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -0,0 +1,348 @@
> +/*
> + * 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
> + */
> +
> +/*
> + * This code handles mapping and unmapping of user data buffers
> + * into DMA'ble space using the IOMMU
> + */
> +
> +#define NPAGE_TO_SIZE(npage)	((size_t)(npage) << PAGE_SHIFT)
> +
> +struct vwork {
> +	struct mm_struct	*mm;
> +	long			npage;
> +	struct work_struct	work;
> +};
> +
> +/* delayed decrement/increment for locked_vm */
> +static void lock_acct_bg(struct work_struct *work)
> +{
> +	struct vwork *vwork = container_of(work, struct vwork, work);
> +	struct mm_struct *mm;
> +
> +	mm = vwork->mm;
> +	down_write(&mm->mmap_sem);
> +	mm->locked_vm += vwork->npage;
> +	up_write(&mm->mmap_sem);
> +	mmput(mm);
> +	kfree(vwork);
> +}
> +
> +static void lock_acct(long npage)
> +{
> +	struct vwork *vwork;
> +	struct mm_struct *mm;
> +
> +	if (!current->mm)
> +		return; /* process exited */
> +
> +	if (down_write_trylock(&current->mm->mmap_sem)) {
> +		current->mm->locked_vm += npage;
> +		up_write(&current->mm->mmap_sem);
> +		return;
> +	}
> +
> +	/*
> +	 * Couldn't get mmap_sem lock, so must setup to update
> +	 * mm->locked_vm later. If locked_vm were atomic, we
> +	 * wouldn't need this silliness
> +	 */
> +	vwork = kmalloc(sizeof(struct vwork), GFP_KERNEL);
> +	if (!vwork)
> +		return;
> +	mm = get_task_mm(current);
> +	if (!mm) {
> +		kfree(vwork);
> +		return;
> +	}
> +	INIT_WORK(&vwork->work, lock_acct_bg);
> +	vwork->mm = mm;
> +	vwork->npage = npage;
> +	schedule_work(&vwork->work);
> +}
> +
> +/*
> + * 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) {
> +		pr_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);
> +	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;
> +	long ret;
> +
> +	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,
> +				dma32_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.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;
> +		unsigned long locked, lock_limit;
> +
> +		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;
> +		else
> +			return -EINVAL;

flags needs to be sanitized too.  Return EINVAL if any unknown bit is
set or else sloppy users may make it very difficult to make use of those
flag bits later.

> +
> +		if ((param.size & ~IOMMU_PAGE_MASK) ||
> +				(param.iova & ~IOMMU_PAGE_MASK) ||
> +				(param.vaddr & ~IOMMU_PAGE_MASK))
> +			return -EINVAL;
> +
> +		if ((param.iova + param.size) >
> +				((tbl->it_offset + tbl->it_size)
> +				<< IOMMU_PAGE_SHIFT))
> +			return -EINVAL;
> +
> +		if (param.iova < (tbl->it_offset << IOMMU_PAGE_SHIFT))
> +			return -EINVAL;
> +
> +		/* Account for locked pages */
> +		locked = current->mm->locked_vm +
> +			(param.size >> PAGE_SHIFT);

If a user were to map only IOMMU_PAGE_SIZE entries on a 64k PAGE_SIZE
system, they'd circumvent this test.

> +		lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> +		if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
> +			pr_warn("RLIMIT_MEMLOCK (%ld) exceeded\n",
> +					rlimit(RLIMIT_MEMLOCK));
> +			return -ENOMEM;
> +		}
> +
> +		ret = iommu_put_tces(tbl, param.iova >> IOMMU_PAGE_SHIFT,
> +				param.vaddr, direction,
> +				param.size >> IOMMU_PAGE_SHIFT);
> +
> +		if (ret > 0)
> +			lock_acct(ret);
> +
> +		return ret;
> +	}
> +	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;
> +
> +		if ((param.size & ~IOMMU_PAGE_MASK) ||
> +				(param.iova & ~IOMMU_PAGE_MASK))
> +			return -EINVAL;
> +
> +		if ((param.iova + param.size) >
> +				((tbl->it_offset + tbl->it_size)
> +				<< IOMMU_PAGE_SHIFT))
> +			return -EINVAL;
> +
> +		if (param.iova < (tbl->it_offset << IOMMU_PAGE_SHIFT))
> +			return -EINVAL;

Sanitize flags here too.

> +
> +		ret = iommu_clear_tces(tbl, param.iova >> IOMMU_PAGE_SHIFT,
> +				param.size >> IOMMU_PAGE_SHIFT);
> +
> +		if (ret > 0)
> +			lock_acct(-ret);
> +
> +		return ret;
> +	}
> +	default:
> +		pr_warn("tce_vfio: unexpected cmd %x\n", cmd);

This is unnecessary additional future maintenance.  You only support
EXTENSION, INFO, MAP, and UNMAP.  It doesn't matter what else gets added
later.

> +	}
> +
> +	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) {
> +		pr_warn("tce_vfio: Only one group per IOMMU container is allowed, existing id=%d, attaching id=%d\n",
> +				iommu_group_id(container->tbl->it_group),
> +				iommu_group_id(iommu_group));
> +		mutex_unlock(&container->lock);
> +		return -EBUSY;
> +	}
> +
> +	container->tbl = tbl;
> +	iommu_reset_table(tbl, false);
> +	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) {
> +		pr_warn("tce_vfio: detaching group #%u, expected group is #%u\n",
> +				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);
> +
> +		container->tbl = NULL;
> +		iommu_reset_table(tbl, true);
> +	}
> +	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..23cfc79 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 +443,33 @@ 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 -------- */
> +
> +/*
> + * The SPAPR TCE info struct provides the information about the PCI bus
> + * address ranges available for DMA, these values are programmed into
> + * the hardware so the guest has to know that information.
> + *
> + * The DMA 32 bit window start is an absolute PCI bus address.
> + * The IOVA address passed via map/unmap ioctls are absolute PCI bus
> + * addresses too so the window works as a filter rather than an offset
> + * for IOVA addresses.
> + *
> + * At the momen the IOMMU page size is 4K.

s/momen/moment/

A flag will need to be added if other page sizes are supported, so as
defined here, it's always 4k.  Thanks,

Alex

> + */
> +struct vfio_iommu_spapr_tce_info {
> +	__u32 argsz;
> +	__u32 flags;			/* reserved for future use */
> +	__u32 dma32_window_start;	/* 32 bit window start (bytes) */
> +	__u32 dma32_window_size;	/* 32 bit window size (bytes) */
> +};
> +
> +#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 */