[v8] dma-mapping: introduce dma_get_iommu_domain()
diff mbox

Message ID 150743420333.12880.6968831423519457797.stgit@dwillia2-desk3.amr.corp.intel.com
State New
Headers show

Commit Message

Dan Williams Oct. 8, 2017, 3:45 a.m. UTC
Add a dma-mapping api helper to retrieve the generic iommu_domain for a device.
The motivation for this interface is making RDMA transfers to DAX mappings
safe. If the DAX file's block map changes we need to be to reliably stop
accesses to blocks that have been freed or re-assigned to a new file. With the
iommu_domain and a callback from the DAX filesystem the kernel can safely
revoke access to a DMA device. The process that performed the RDMA memory
registration is also notified of this revocation event, but the kernel can not
otherwise be in the position of waiting for userspace to quiesce the device.

Since PMEM+DAX is currently only enabled for x86, we only update the x86
iommu drivers.

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
Changes since v7:
* retrieve the iommu_domain so that we can later pass the results of
  dma_map_* to iommu_unmap() in advance of the actual dma_unmap_*.

 drivers/base/dma-mapping.c  |   10 ++++++++++
 drivers/iommu/amd_iommu.c   |   10 ++++++++++
 drivers/iommu/intel-iommu.c |   15 +++++++++++++++
 include/linux/dma-mapping.h |    3 +++
 4 files changed, 38 insertions(+)


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Comments

Robin Murphy Oct. 9, 2017, 10:37 a.m. UTC | #1
Hi Dan,

On 08/10/17 04:45, Dan Williams wrote:
> Add a dma-mapping api helper to retrieve the generic iommu_domain for a device.
> The motivation for this interface is making RDMA transfers to DAX mappings
> safe. If the DAX file's block map changes we need to be to reliably stop
> accesses to blocks that have been freed or re-assigned to a new file.

...which is also going to require some way to force the IOMMU drivers
(on x86 at least) to do a fully-synchronous unmap, instead of just
throwing the IOVA onto a flush queue to invalidate the TLBs at some
point in the future. Assuming of course that there's an IOMMU both
present and performing DMA translation in the first place.

> With the
> iommu_domain and a callback from the DAX filesystem the kernel can safely
> revoke access to a DMA device. The process that performed the RDMA memory
> registration is also notified of this revocation event, but the kernel can not
> otherwise be in the position of waiting for userspace to quiesce the device.

OK, but why reinvent iommu_get_domain_for_dev()?

> Since PMEM+DAX is currently only enabled for x86, we only update the x86
> iommu drivers.

Note in particular that those two drivers happen to be the *only* place
this approach could work - everyone else is going to have to fall back
to the generic IOMMU API function anyway.

Robin.

> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: Ashok Raj <ashok.raj@intel.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> Changes since v7:
> * retrieve the iommu_domain so that we can later pass the results of
>   dma_map_* to iommu_unmap() in advance of the actual dma_unmap_*.
> 
>  drivers/base/dma-mapping.c  |   10 ++++++++++
>  drivers/iommu/amd_iommu.c   |   10 ++++++++++
>  drivers/iommu/intel-iommu.c |   15 +++++++++++++++
>  include/linux/dma-mapping.h |    3 +++
>  4 files changed, 38 insertions(+)
> 
> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
> index e584eddef0a7..fdb9764f95a4 100644
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
> @@ -369,3 +369,13 @@ void dma_deconfigure(struct device *dev)
>  	of_dma_deconfigure(dev);
>  	acpi_dma_deconfigure(dev);
>  }
> +
> +struct iommu_domain *dma_get_iommu_domain(struct device *dev)
> +{
> +	const struct dma_map_ops *ops = get_dma_ops(dev);
> +
> +	if (ops && ops->get_iommu)
> +		return ops->get_iommu(dev);
> +	return NULL;
> +}
> +EXPORT_SYMBOL(dma_get_iommu_domain);
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 51f8215877f5..c8e1a45af182 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -2271,6 +2271,15 @@ static struct protection_domain *get_domain(struct device *dev)
>  	return domain;
>  }
>  
> +static struct iommu_domain *amd_dma_get_iommu(struct device *dev)
> +{
> +	struct protection_domain *domain = get_domain(dev);
> +
> +	if (IS_ERR(domain))
> +		return NULL;
> +	return &domain->domain;
> +}
> +
>  static void update_device_table(struct protection_domain *domain)
>  {
>  	struct iommu_dev_data *dev_data;
> @@ -2689,6 +2698,7 @@ static const struct dma_map_ops amd_iommu_dma_ops = {
>  	.unmap_sg	= unmap_sg,
>  	.dma_supported	= amd_iommu_dma_supported,
>  	.mapping_error	= amd_iommu_mapping_error,
> +	.get_iommu	= amd_dma_get_iommu,
>  };
>  
>  static int init_reserved_iova_ranges(void)
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 6784a05dd6b2..f3f4939cebad 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -3578,6 +3578,20 @@ static int iommu_no_mapping(struct device *dev)
>  	return 0;
>  }
>  
> +static struct iommu_domain *intel_dma_get_iommu(struct device *dev)
> +{
> +	struct dmar_domain *domain;
> +
> +	if (iommu_no_mapping(dev))
> +		return NULL;
> +
> +	domain = get_valid_domain_for_dev(dev);
> +	if (!domain)
> +		return NULL;
> +
> +	return &domain->domain;
> +}
> +
>  static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr,
>  				     size_t size, int dir, u64 dma_mask)
>  {
> @@ -3872,6 +3886,7 @@ const struct dma_map_ops intel_dma_ops = {
>  	.map_page = intel_map_page,
>  	.unmap_page = intel_unmap_page,
>  	.mapping_error = intel_mapping_error,
> +	.get_iommu = intel_dma_get_iommu,
>  #ifdef CONFIG_X86
>  	.dma_supported = x86_dma_supported,
>  #endif
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 29ce9815da87..aa62df1d0d72 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -128,6 +128,7 @@ struct dma_map_ops {
>  				   enum dma_data_direction dir);
>  	int (*mapping_error)(struct device *dev, dma_addr_t dma_addr);
>  	int (*dma_supported)(struct device *dev, u64 mask);
> +	struct iommu_domain *(*get_iommu)(struct device *dev);
>  #ifdef ARCH_HAS_DMA_GET_REQUIRED_MASK
>  	u64 (*get_required_mask)(struct device *dev);
>  #endif
> @@ -221,6 +222,8 @@ static inline const struct dma_map_ops *get_dma_ops(struct device *dev)
>  }
>  #endif
>  
> +extern struct iommu_domain *dma_get_iommu_domain(struct device *dev);
> +
>  static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
>  					      size_t size,
>  					      enum dma_data_direction dir,
> 

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Dan Williams Oct. 9, 2017, 5:32 p.m. UTC | #2
On Mon, Oct 9, 2017 at 3:37 AM, Robin Murphy <robin.murphy@arm.com> wrote:
> Hi Dan,
>
> On 08/10/17 04:45, Dan Williams wrote:
>> Add a dma-mapping api helper to retrieve the generic iommu_domain for a device.
>> The motivation for this interface is making RDMA transfers to DAX mappings
>> safe. If the DAX file's block map changes we need to be to reliably stop
>> accesses to blocks that have been freed or re-assigned to a new file.
>
> ...which is also going to require some way to force the IOMMU drivers
> (on x86 at least) to do a fully-synchronous unmap, instead of just
> throwing the IOVA onto a flush queue to invalidate the TLBs at some
> point in the future.

Isn't that the difference between iommu_unmap() and
iommu_unmap_fast()? As far as I can tell amd-iommu and intel-iommu
both flush iotlbs on iommu_unmap() and don't support fast unmaps.

> Assuming of course that there's an IOMMU both
> present and performing DMA translation in the first place.

That's why I want to call through the dma api to see if the iommu is
being used to satisfy dma mappings.

>> With the
>> iommu_domain and a callback from the DAX filesystem the kernel can safely
>> revoke access to a DMA device. The process that performed the RDMA memory
>> registration is also notified of this revocation event, but the kernel can not
>> otherwise be in the position of waiting for userspace to quiesce the device.
>
> OK, but why reinvent iommu_get_domain_for_dev()?

How do I know if the iommu returned from that routine is the one being
used for dma mapping operations for the device? Specifically, how
would I discover that the result of dma_map_sg() can be passed as an
IOVA range to iommu_unmap()?

>> Since PMEM+DAX is currently only enabled for x86, we only update the x86
>> iommu drivers.
>
> Note in particular that those two drivers happen to be the *only* place
> this approach could work - everyone else is going to have to fall back
> to the generic IOMMU API function anyway.

I want to make this functionality generic, but I'm not familiar with
the iommu sub-system. How are dma mapping operations routed to the
iommu driver in those other imlementations?
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Raj, Ashok Oct. 10, 2017, 2:40 p.m. UTC | #3
Hi Dan

On Sat, Oct 07, 2017 at 08:45:00PM -0700, Dan Williams wrote:
> Add a dma-mapping api helper to retrieve the generic iommu_domain for a device.
> The motivation for this interface is making RDMA transfers to DAX mappings
> safe. If the DAX file's block map changes we need to be to reliably stop
> accesses to blocks that have been freed or re-assigned to a new file. With the
> iommu_domain and a callback from the DAX filesystem the kernel can safely
> revoke access to a DMA device. The process that performed the RDMA memory
> registration is also notified of this revocation event, but the kernel can not
> otherwise be in the position of waiting for userspace to quiesce the device.
> 
> Since PMEM+DAX is currently only enabled for x86, we only update the x86
> iommu drivers.
> 
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: Ashok Raj <ashok.raj@intel.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> Changes since v7:
> * retrieve the iommu_domain so that we can later pass the results of
>   dma_map_* to iommu_unmap() in advance of the actual dma_unmap_*.
> 
>  drivers/base/dma-mapping.c  |   10 ++++++++++
>  drivers/iommu/amd_iommu.c   |   10 ++++++++++
>  drivers/iommu/intel-iommu.c |   15 +++++++++++++++
>  include/linux/dma-mapping.h |    3 +++
>  4 files changed, 38 insertions(+)
> 
> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
> index e584eddef0a7..fdb9764f95a4 100644
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
> @@ -369,3 +369,13 @@ void dma_deconfigure(struct device *dev)
>  	of_dma_deconfigure(dev);
>  	acpi_dma_deconfigure(dev);
>  }
> +
> +struct iommu_domain *dma_get_iommu_domain(struct device *dev)
> +{
> +	const struct dma_map_ops *ops = get_dma_ops(dev);
> +
> +	if (ops && ops->get_iommu)
> +		return ops->get_iommu(dev);
> +	return NULL;
> +}
> +EXPORT_SYMBOL(dma_get_iommu_domain);
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 51f8215877f5..c8e1a45af182 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -2271,6 +2271,15 @@ static struct protection_domain *get_domain(struct device *dev)
>  	return domain;
>  }
>  
> +static struct iommu_domain *amd_dma_get_iommu(struct device *dev)

Minor: Do you want to keep the naming consistent.. amd_dma_get_domain() vs
get_iommu?

> +{
> +	struct protection_domain *domain = get_domain(dev);
> +
> +	if (IS_ERR(domain))
> +		return NULL;
> +	return &domain->domain;
> +}
> +
>  static void update_device_table(struct protection_domain *domain)
>  {
>  	struct iommu_dev_data *dev_data;
> @@ -2689,6 +2698,7 @@ static const struct dma_map_ops amd_iommu_dma_ops = {
>  	.unmap_sg	= unmap_sg,
>  	.dma_supported	= amd_iommu_dma_supported,
>  	.mapping_error	= amd_iommu_mapping_error,
> +	.get_iommu	= amd_dma_get_iommu,

ditto for here and other places below:

>  };
>  
>  static int init_reserved_iova_ranges(void)
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 6784a05dd6b2..f3f4939cebad 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -3578,6 +3578,20 @@ static int iommu_no_mapping(struct device *dev)
>  	return 0;
>  }
>  
> +static struct iommu_domain *intel_dma_get_iommu(struct device *dev)
> +{
> +	struct dmar_domain *domain;
> +
> +	if (iommu_no_mapping(dev))
> +		return NULL;
> +
> +	domain = get_valid_domain_for_dev(dev);
> +	if (!domain)
> +		return NULL;
> +
> +	return &domain->domain;
> +}
> +
>  static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr,
>  				     size_t size, int dir, u64 dma_mask)
>  {
> @@ -3872,6 +3886,7 @@ const struct dma_map_ops intel_dma_ops = {
>  	.map_page = intel_map_page,
>  	.unmap_page = intel_unmap_page,
>  	.mapping_error = intel_mapping_error,
> +	.get_iommu = intel_dma_get_iommu,
>  #ifdef CONFIG_X86
>  	.dma_supported = x86_dma_supported,
>  #endif
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 29ce9815da87..aa62df1d0d72 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -128,6 +128,7 @@ struct dma_map_ops {
>  				   enum dma_data_direction dir);
>  	int (*mapping_error)(struct device *dev, dma_addr_t dma_addr);
>  	int (*dma_supported)(struct device *dev, u64 mask);
> +	struct iommu_domain *(*get_iommu)(struct device *dev);
>  #ifdef ARCH_HAS_DMA_GET_REQUIRED_MASK
>  	u64 (*get_required_mask)(struct device *dev);
>  #endif
> @@ -221,6 +222,8 @@ static inline const struct dma_map_ops *get_dma_ops(struct device *dev)
>  }
>  #endif
>  
> +extern struct iommu_domain *dma_get_iommu_domain(struct device *dev);
> +
>  static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
>  					      size_t size,
>  					      enum dma_data_direction dir,
> 
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Patch
diff mbox

diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
index e584eddef0a7..fdb9764f95a4 100644
--- a/drivers/base/dma-mapping.c
+++ b/drivers/base/dma-mapping.c
@@ -369,3 +369,13 @@  void dma_deconfigure(struct device *dev)
 	of_dma_deconfigure(dev);
 	acpi_dma_deconfigure(dev);
 }
+
+struct iommu_domain *dma_get_iommu_domain(struct device *dev)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	if (ops && ops->get_iommu)
+		return ops->get_iommu(dev);
+	return NULL;
+}
+EXPORT_SYMBOL(dma_get_iommu_domain);
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 51f8215877f5..c8e1a45af182 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2271,6 +2271,15 @@  static struct protection_domain *get_domain(struct device *dev)
 	return domain;
 }
 
+static struct iommu_domain *amd_dma_get_iommu(struct device *dev)
+{
+	struct protection_domain *domain = get_domain(dev);
+
+	if (IS_ERR(domain))
+		return NULL;
+	return &domain->domain;
+}
+
 static void update_device_table(struct protection_domain *domain)
 {
 	struct iommu_dev_data *dev_data;
@@ -2689,6 +2698,7 @@  static const struct dma_map_ops amd_iommu_dma_ops = {
 	.unmap_sg	= unmap_sg,
 	.dma_supported	= amd_iommu_dma_supported,
 	.mapping_error	= amd_iommu_mapping_error,
+	.get_iommu	= amd_dma_get_iommu,
 };
 
 static int init_reserved_iova_ranges(void)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 6784a05dd6b2..f3f4939cebad 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3578,6 +3578,20 @@  static int iommu_no_mapping(struct device *dev)
 	return 0;
 }
 
+static struct iommu_domain *intel_dma_get_iommu(struct device *dev)
+{
+	struct dmar_domain *domain;
+
+	if (iommu_no_mapping(dev))
+		return NULL;
+
+	domain = get_valid_domain_for_dev(dev);
+	if (!domain)
+		return NULL;
+
+	return &domain->domain;
+}
+
 static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr,
 				     size_t size, int dir, u64 dma_mask)
 {
@@ -3872,6 +3886,7 @@  const struct dma_map_ops intel_dma_ops = {
 	.map_page = intel_map_page,
 	.unmap_page = intel_unmap_page,
 	.mapping_error = intel_mapping_error,
+	.get_iommu = intel_dma_get_iommu,
 #ifdef CONFIG_X86
 	.dma_supported = x86_dma_supported,
 #endif
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 29ce9815da87..aa62df1d0d72 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -128,6 +128,7 @@  struct dma_map_ops {
 				   enum dma_data_direction dir);
 	int (*mapping_error)(struct device *dev, dma_addr_t dma_addr);
 	int (*dma_supported)(struct device *dev, u64 mask);
+	struct iommu_domain *(*get_iommu)(struct device *dev);
 #ifdef ARCH_HAS_DMA_GET_REQUIRED_MASK
 	u64 (*get_required_mask)(struct device *dev);
 #endif
@@ -221,6 +222,8 @@  static inline const struct dma_map_ops *get_dma_ops(struct device *dev)
 }
 #endif
 
+extern struct iommu_domain *dma_get_iommu_domain(struct device *dev);
+
 static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
 					      size_t size,
 					      enum dma_data_direction dir,