diff mbox

[RFC,v3,05/15] iommu/arm-smmu: implement alloc/free_reserved_iova_domain

Message ID 1455264797-2334-6-git-send-email-eric.auger@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Eric Auger Feb. 12, 2016, 8:13 a.m. UTC
Implement alloc/free_reserved_iova_domain for arm-smmu. we use
the iova allocator (iova.c). The iova_domain is attached to the
arm_smmu_domain struct. A mutex is introduced to protect it.

Signed-off-by: Eric Auger <eric.auger@linaro.org>

---
v2 -> v3:
- select IOMMU_IOVA when ARM_SMMU or ARM_SMMU_V3 is set

v1 -> v2:
- formerly implemented in vfio_iommu_type1
---
 drivers/iommu/Kconfig    |  2 ++
 drivers/iommu/arm-smmu.c | 87 +++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 74 insertions(+), 15 deletions(-)

Comments

Robin Murphy Feb. 18, 2016, 11:09 a.m. UTC | #1
Hi Eric,

On 12/02/16 08:13, Eric Auger wrote:
> Implement alloc/free_reserved_iova_domain for arm-smmu. we use
> the iova allocator (iova.c). The iova_domain is attached to the
> arm_smmu_domain struct. A mutex is introduced to protect it.

The IOMMU API currently leaves IOVA management entirely up to the caller 
- VFIO is already managing its own IOVA space, so what warrants this 
being pushed all the way down to the IOMMU driver? All I see here is 
abstract code with no hardware-specific details that'll have to be 
copy-pasted into other IOMMU drivers (e.g. SMMUv3), which strongly 
suggests it's the wrong place to do it.

As I understand the problem, VFIO has a generic "configure an IOMMU to 
point at an MSI doorbell" step to do in the process of attaching a 
device, which hasn't needed implementing yet due to VT-d's 
IOMMU_CAP_I_AM_ALSO_ACTUALLY_THE_MSI_CONTROLLER_IN_DISGUISE flag, which 
most of us have managed to misinterpret so far. AFAICS all the IOMMU 
driver should need to know about this is an iommu_map() call (which will 
want a slight extension[1] to make things behave properly). We should be 
fixing the abstraction to be less x86-centric, not hacking up all the 
ARM drivers to emulate x86 hardware behaviour in software.

Robin.

[1]:http://article.gmane.org/gmane.linux.kernel.cross-arch/30833

> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>
> ---
> v2 -> v3:
> - select IOMMU_IOVA when ARM_SMMU or ARM_SMMU_V3 is set
>
> v1 -> v2:
> - formerly implemented in vfio_iommu_type1
> ---
>   drivers/iommu/Kconfig    |  2 ++
>   drivers/iommu/arm-smmu.c | 87 +++++++++++++++++++++++++++++++++++++++---------
>   2 files changed, 74 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index a1e75cb..1106528 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -289,6 +289,7 @@ config ARM_SMMU
>   	bool "ARM Ltd. System MMU (SMMU) Support"
>   	depends on (ARM64 || ARM) && MMU
>   	select IOMMU_API
> +	select IOMMU_IOVA
>   	select IOMMU_IO_PGTABLE_LPAE
>   	select ARM_DMA_USE_IOMMU if ARM
>   	help
> @@ -302,6 +303,7 @@ config ARM_SMMU_V3
>   	bool "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
>   	depends on ARM64 && PCI
>   	select IOMMU_API
> +	select IOMMU_IOVA
>   	select IOMMU_IO_PGTABLE_LPAE
>   	select GENERIC_MSI_IRQ_DOMAIN
>   	help
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index c8b7e71..f42341d 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -42,6 +42,7 @@
>   #include <linux/platform_device.h>
>   #include <linux/slab.h>
>   #include <linux/spinlock.h>
> +#include <linux/iova.h>
>
>   #include <linux/amba/bus.h>
>
> @@ -347,6 +348,9 @@ struct arm_smmu_domain {
>   	enum arm_smmu_domain_stage	stage;
>   	struct mutex			init_mutex; /* Protects smmu pointer */
>   	struct iommu_domain		domain;
> +	struct iova_domain		*reserved_iova_domain;
> +	/* protects reserved domain manipulation */
> +	struct mutex			reserved_mutex;
>   };
>
>   static struct iommu_ops arm_smmu_ops;
> @@ -975,6 +979,7 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
>   		return NULL;
>
>   	mutex_init(&smmu_domain->init_mutex);
> +	mutex_init(&smmu_domain->reserved_mutex);
>   	spin_lock_init(&smmu_domain->pgtbl_lock);
>
>   	return &smmu_domain->domain;
> @@ -1446,22 +1451,74 @@ out_unlock:
>   	return ret;
>   }
>
> +static int arm_smmu_alloc_reserved_iova_domain(struct iommu_domain *domain,
> +					       dma_addr_t iova, size_t size,
> +					       unsigned long order)
> +{
> +	unsigned long granule, mask;
> +	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> +	int ret = 0;
> +
> +	granule = 1UL << order;
> +	mask = granule - 1;
> +	if (iova & mask || (!size) || (size & mask))
> +		return -EINVAL;
> +
> +	if (smmu_domain->reserved_iova_domain)
> +		return -EEXIST;
> +
> +	mutex_lock(&smmu_domain->reserved_mutex);
> +
> +	smmu_domain->reserved_iova_domain =
> +		kzalloc(sizeof(struct iova_domain), GFP_KERNEL);
> +	if (!smmu_domain->reserved_iova_domain) {
> +		ret = -ENOMEM;
> +		goto unlock;
> +	}
> +
> +	init_iova_domain(smmu_domain->reserved_iova_domain,
> +			 granule, iova >> order, (iova + size - 1) >> order);
> +
> +unlock:
> +	mutex_unlock(&smmu_domain->reserved_mutex);
> +	return ret;
> +}
> +
> +static void arm_smmu_free_reserved_iova_domain(struct iommu_domain *domain)
> +{
> +	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> +	struct iova_domain *iovad = smmu_domain->reserved_iova_domain;
> +
> +	if (!iovad)
> +		return;
> +
> +	mutex_lock(&smmu_domain->reserved_mutex);
> +
> +	put_iova_domain(iovad);
> +	kfree(iovad);
> +
> +	mutex_unlock(&smmu_domain->reserved_mutex);
> +}
> +
>   static struct iommu_ops arm_smmu_ops = {
> -	.capable		= arm_smmu_capable,
> -	.domain_alloc		= arm_smmu_domain_alloc,
> -	.domain_free		= arm_smmu_domain_free,
> -	.attach_dev		= arm_smmu_attach_dev,
> -	.detach_dev		= arm_smmu_detach_dev,
> -	.map			= arm_smmu_map,
> -	.unmap			= arm_smmu_unmap,
> -	.map_sg			= default_iommu_map_sg,
> -	.iova_to_phys		= arm_smmu_iova_to_phys,
> -	.add_device		= arm_smmu_add_device,
> -	.remove_device		= arm_smmu_remove_device,
> -	.device_group		= arm_smmu_device_group,
> -	.domain_get_attr	= arm_smmu_domain_get_attr,
> -	.domain_set_attr	= arm_smmu_domain_set_attr,
> -	.pgsize_bitmap		= -1UL, /* Restricted during device attach */
> +	.capable			= arm_smmu_capable,
> +	.domain_alloc			= arm_smmu_domain_alloc,
> +	.domain_free			= arm_smmu_domain_free,
> +	.attach_dev			= arm_smmu_attach_dev,
> +	.detach_dev			= arm_smmu_detach_dev,
> +	.map				= arm_smmu_map,
> +	.unmap				= arm_smmu_unmap,
> +	.map_sg				= default_iommu_map_sg,
> +	.iova_to_phys			= arm_smmu_iova_to_phys,
> +	.add_device			= arm_smmu_add_device,
> +	.remove_device			= arm_smmu_remove_device,
> +	.device_group			= arm_smmu_device_group,
> +	.domain_get_attr		= arm_smmu_domain_get_attr,
> +	.domain_set_attr		= arm_smmu_domain_set_attr,
> +	.alloc_reserved_iova_domain	= arm_smmu_alloc_reserved_iova_domain,
> +	.free_reserved_iova_domain	= arm_smmu_free_reserved_iova_domain,
> +	/* Page size bitmap, restricted during device attach */
> +	.pgsize_bitmap			= -1UL,
>   };
>
>   static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
>
Eric Auger Feb. 18, 2016, 3:22 p.m. UTC | #2
Hi Robin,
On 02/18/2016 12:09 PM, Robin Murphy wrote:
> Hi Eric,
> 
> On 12/02/16 08:13, Eric Auger wrote:
>> Implement alloc/free_reserved_iova_domain for arm-smmu. we use
>> the iova allocator (iova.c). The iova_domain is attached to the
>> arm_smmu_domain struct. A mutex is introduced to protect it.
> 
> The IOMMU API currently leaves IOVA management entirely up to the caller
I agree

> - VFIO is already managing its own IOVA space, so what warrants this
> being pushed all the way down to the IOMMU driver?
In practice, with upstreamed code, VFIO uses IOVA = GPA provided by the
user-space (corresponding to RAM regions) and does not allocate IOVA
itself. The IOVA is passed through the VFIO_IOMMU_MAP_DMA ioctl.

With that series we propose that the user-space provides a pool of
unused IOVA that can be used to map Host physical addresses (MSI frame
address). So effectively someone needs to use an iova allocator to
allocate within that window. This can be vfio or the iommu driver. But
in both cases this is a new capability introduced in either component.

In the first version of this series
(https://lkml.org/lkml/2016/1/26/371) I put this iova allocation in
vfio_iommu_type1. the vfio-pci driver then was using this vfio internal
API to overwrite the physical address written in the PCI device by the
MSI controller.

However I was advised by Alex to move things at a lower level
(http://www.spinics.net/lists/kvm/msg126809.html), IOMMU core or irq
remapping driver; also the MSI controller should directly program the
IOVA address in the PCI device.

On ARM, irq remapping is somehow abstracted in ITS driver. Also we need
that functionality in GICv2M so I eventually chose to put the
functionality in the IOMMU driver. Since iova.c is not compiled by
everyone and since that functionality is needed for a restricted set of
architectures, ARM/ARM64 & PowerPC I chose to implement this in arhc
specific code, for the time being in arm-smmu.c.

This allows the MSI controller to interact with the IOMMU API to bind
its MSI address. I think it may be feasible to have the MSI controller
interact with the vfio external user API but does it look better?

Assuming we can agree on the relevance of adding that functionality at
IOMMU API level, maybe we can create a separate .c file to share code
between arm-smmu and arm-smmu-v3.c? or even I could dare to add this
into the iommu generic part. What is your opinion?

 All I see here is
> abstract code with no hardware-specific details that'll have to be
> copy-pasted into other IOMMU drivers (e.g. SMMUv3), which strongly
> suggests it's the wrong place to do it.
> 
> As I understand the problem, VFIO has a generic "configure an IOMMU to
> point at an MSI doorbell" step to do in the process of attaching a
> device, which hasn't needed implementing yet due to VT-d's
> IOMMU_CAP_I_AM_ALSO_ACTUALLY_THE_MSI_CONTROLLER_IN_DISGUISE flag, which
> most of us have managed to misinterpret so far.

Maybe I misunderstood the above comment but I would say this is the
contrary: ie up to now, VFIO did not need to care about that issue since
MSI addresses were not mapped in the IOMMU on x86. Now they need to be
so we need to extend an existing API, would it be VFIO external user API
or IOMMU API. But please correct if I misunderstood you.

Also I found it more practical to have a all-in-one API doing both the
iova allocation and binding (dma_map_single like). the user of the API
does not have to care about the iommu page size.

Thanks for your time and looking forward to reading from you!

Best Regards

Eric

 AFAICS all the IOMMU
> driver should need to know about this is an iommu_map() call (which will
> want a slight extension[1] to make things behave properly). We should be
> fixing the abstraction to be less x86-centric, not hacking up all the
> ARM drivers to emulate x86 hardware behaviour in software.
> 
> Robin.
> 
> [1]:http://article.gmane.org/gmane.linux.kernel.cross-arch/30833
> 
>> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>>
>> ---
>> v2 -> v3:
>> - select IOMMU_IOVA when ARM_SMMU or ARM_SMMU_V3 is set
>>
>> v1 -> v2:
>> - formerly implemented in vfio_iommu_type1
>> ---
>>   drivers/iommu/Kconfig    |  2 ++
>>   drivers/iommu/arm-smmu.c | 87
>> +++++++++++++++++++++++++++++++++++++++---------
>>   2 files changed, 74 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
>> index a1e75cb..1106528 100644
>> --- a/drivers/iommu/Kconfig
>> +++ b/drivers/iommu/Kconfig
>> @@ -289,6 +289,7 @@ config ARM_SMMU
>>       bool "ARM Ltd. System MMU (SMMU) Support"
>>       depends on (ARM64 || ARM) && MMU
>>       select IOMMU_API
>> +    select IOMMU_IOVA
>>       select IOMMU_IO_PGTABLE_LPAE
>>       select ARM_DMA_USE_IOMMU if ARM
>>       help
>> @@ -302,6 +303,7 @@ config ARM_SMMU_V3
>>       bool "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
>>       depends on ARM64 && PCI
>>       select IOMMU_API
>> +    select IOMMU_IOVA
>>       select IOMMU_IO_PGTABLE_LPAE
>>       select GENERIC_MSI_IRQ_DOMAIN
>>       help
>> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
>> index c8b7e71..f42341d 100644
>> --- a/drivers/iommu/arm-smmu.c
>> +++ b/drivers/iommu/arm-smmu.c
>> @@ -42,6 +42,7 @@
>>   #include <linux/platform_device.h>
>>   #include <linux/slab.h>
>>   #include <linux/spinlock.h>
>> +#include <linux/iova.h>
>>
>>   #include <linux/amba/bus.h>
>>
>> @@ -347,6 +348,9 @@ struct arm_smmu_domain {
>>       enum arm_smmu_domain_stage    stage;
>>       struct mutex            init_mutex; /* Protects smmu pointer */
>>       struct iommu_domain        domain;
>> +    struct iova_domain        *reserved_iova_domain;
>> +    /* protects reserved domain manipulation */
>> +    struct mutex            reserved_mutex;
>>   };
>>
>>   static struct iommu_ops arm_smmu_ops;
>> @@ -975,6 +979,7 @@ static struct iommu_domain
>> *arm_smmu_domain_alloc(unsigned type)
>>           return NULL;
>>
>>       mutex_init(&smmu_domain->init_mutex);
>> +    mutex_init(&smmu_domain->reserved_mutex);
>>       spin_lock_init(&smmu_domain->pgtbl_lock);
>>
>>       return &smmu_domain->domain;
>> @@ -1446,22 +1451,74 @@ out_unlock:
>>       return ret;
>>   }
>>
>> +static int arm_smmu_alloc_reserved_iova_domain(struct iommu_domain
>> *domain,
>> +                           dma_addr_t iova, size_t size,
>> +                           unsigned long order)
>> +{
>> +    unsigned long granule, mask;
>> +    struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>> +    int ret = 0;
>> +
>> +    granule = 1UL << order;
>> +    mask = granule - 1;
>> +    if (iova & mask || (!size) || (size & mask))
>> +        return -EINVAL;
>> +
>> +    if (smmu_domain->reserved_iova_domain)
>> +        return -EEXIST;
>> +
>> +    mutex_lock(&smmu_domain->reserved_mutex);
>> +
>> +    smmu_domain->reserved_iova_domain =
>> +        kzalloc(sizeof(struct iova_domain), GFP_KERNEL);
>> +    if (!smmu_domain->reserved_iova_domain) {
>> +        ret = -ENOMEM;
>> +        goto unlock;
>> +    }
>> +
>> +    init_iova_domain(smmu_domain->reserved_iova_domain,
>> +             granule, iova >> order, (iova + size - 1) >> order);
>> +
>> +unlock:
>> +    mutex_unlock(&smmu_domain->reserved_mutex);
>> +    return ret;
>> +}
>> +
>> +static void arm_smmu_free_reserved_iova_domain(struct iommu_domain
>> *domain)
>> +{
>> +    struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>> +    struct iova_domain *iovad = smmu_domain->reserved_iova_domain;
>> +
>> +    if (!iovad)
>> +        return;
>> +
>> +    mutex_lock(&smmu_domain->reserved_mutex);
>> +
>> +    put_iova_domain(iovad);
>> +    kfree(iovad);
>> +
>> +    mutex_unlock(&smmu_domain->reserved_mutex);
>> +}
>> +
>>   static struct iommu_ops arm_smmu_ops = {
>> -    .capable        = arm_smmu_capable,
>> -    .domain_alloc        = arm_smmu_domain_alloc,
>> -    .domain_free        = arm_smmu_domain_free,
>> -    .attach_dev        = arm_smmu_attach_dev,
>> -    .detach_dev        = arm_smmu_detach_dev,
>> -    .map            = arm_smmu_map,
>> -    .unmap            = arm_smmu_unmap,
>> -    .map_sg            = default_iommu_map_sg,
>> -    .iova_to_phys        = arm_smmu_iova_to_phys,
>> -    .add_device        = arm_smmu_add_device,
>> -    .remove_device        = arm_smmu_remove_device,
>> -    .device_group        = arm_smmu_device_group,
>> -    .domain_get_attr    = arm_smmu_domain_get_attr,
>> -    .domain_set_attr    = arm_smmu_domain_set_attr,
>> -    .pgsize_bitmap        = -1UL, /* Restricted during device attach */
>> +    .capable            = arm_smmu_capable,
>> +    .domain_alloc            = arm_smmu_domain_alloc,
>> +    .domain_free            = arm_smmu_domain_free,
>> +    .attach_dev            = arm_smmu_attach_dev,
>> +    .detach_dev            = arm_smmu_detach_dev,
>> +    .map                = arm_smmu_map,
>> +    .unmap                = arm_smmu_unmap,
>> +    .map_sg                = default_iommu_map_sg,
>> +    .iova_to_phys            = arm_smmu_iova_to_phys,
>> +    .add_device            = arm_smmu_add_device,
>> +    .remove_device            = arm_smmu_remove_device,
>> +    .device_group            = arm_smmu_device_group,
>> +    .domain_get_attr        = arm_smmu_domain_get_attr,
>> +    .domain_set_attr        = arm_smmu_domain_set_attr,
>> +    .alloc_reserved_iova_domain    =
>> arm_smmu_alloc_reserved_iova_domain,
>> +    .free_reserved_iova_domain    = arm_smmu_free_reserved_iova_domain,
>> +    /* Page size bitmap, restricted during device attach */
>> +    .pgsize_bitmap            = -1UL,
>>   };
>>
>>   static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
>>
>
Alex Williamson Feb. 18, 2016, 4:06 p.m. UTC | #3
On Thu, 18 Feb 2016 11:09:17 +0000
Robin Murphy <robin.murphy@arm.com> wrote:

> Hi Eric,
> 
> On 12/02/16 08:13, Eric Auger wrote:
> > Implement alloc/free_reserved_iova_domain for arm-smmu. we use
> > the iova allocator (iova.c). The iova_domain is attached to the
> > arm_smmu_domain struct. A mutex is introduced to protect it.  
> 
> The IOMMU API currently leaves IOVA management entirely up to the caller 
> - VFIO is already managing its own IOVA space, so what warrants this 
> being pushed all the way down to the IOMMU driver? All I see here is 
> abstract code with no hardware-specific details that'll have to be 
> copy-pasted into other IOMMU drivers (e.g. SMMUv3), which strongly 
> suggests it's the wrong place to do it.
> 
> As I understand the problem, VFIO has a generic "configure an IOMMU to 
> point at an MSI doorbell" step to do in the process of attaching a 
> device, which hasn't needed implementing yet due to VT-d's 
> IOMMU_CAP_I_AM_ALSO_ACTUALLY_THE_MSI_CONTROLLER_IN_DISGUISE flag, which 
> most of us have managed to misinterpret so far. AFAICS all the IOMMU 
> driver should need to know about this is an iommu_map() call (which will 
> want a slight extension[1] to make things behave properly). We should be 
> fixing the abstraction to be less x86-centric, not hacking up all the 
> ARM drivers to emulate x86 hardware behaviour in software.

The gap I see is that, that the I_AM_ALSO_ACTUALLY_THE_MSI...
solution transparently fixes, is that there's no connection between
pci_enable_msi{x}_range and the IOMMU API.  If I want to allow a device
managed by an IOMMU API domain to perform MSI, I need to go scrape the
MSI vectors out of the device, setup a translation into my IOVA space,
and re-write those vectors.  Not to mention that as an end user, I
have no idea what might be sharing the page where those vectors are
targeted and what I might be allowing the user DMA access to.  MSI
setup is necessarily making use of the IOVA space of the device, so
there's clearly an opportunity to interact with the IOMMU API to manage
that IOVA usage.  x86 has an implicit range of IOVA space for MSI, this
makes an explicit range, reserved by the IOMMU API user for this
purpose.  At the vfio level, I just want to be able to call the PCI
MSI/X setup routines and have them automatically program vectors that
make use of IOVA space that I've already marked reserved for this
purpose.  I don't see how that's x86-centric other than x86 has already
managed to make this transparent and spoiled users into expecting
working IOVAs on the device after using standard MSI vector setup
callbacks.  That's the goal I'm looking for.  Thanks,

Alex
diff mbox

Patch

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index a1e75cb..1106528 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -289,6 +289,7 @@  config ARM_SMMU
 	bool "ARM Ltd. System MMU (SMMU) Support"
 	depends on (ARM64 || ARM) && MMU
 	select IOMMU_API
+	select IOMMU_IOVA
 	select IOMMU_IO_PGTABLE_LPAE
 	select ARM_DMA_USE_IOMMU if ARM
 	help
@@ -302,6 +303,7 @@  config ARM_SMMU_V3
 	bool "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
 	depends on ARM64 && PCI
 	select IOMMU_API
+	select IOMMU_IOVA
 	select IOMMU_IO_PGTABLE_LPAE
 	select GENERIC_MSI_IRQ_DOMAIN
 	help
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index c8b7e71..f42341d 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -42,6 +42,7 @@ 
 #include <linux/platform_device.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/iova.h>
 
 #include <linux/amba/bus.h>
 
@@ -347,6 +348,9 @@  struct arm_smmu_domain {
 	enum arm_smmu_domain_stage	stage;
 	struct mutex			init_mutex; /* Protects smmu pointer */
 	struct iommu_domain		domain;
+	struct iova_domain		*reserved_iova_domain;
+	/* protects reserved domain manipulation */
+	struct mutex			reserved_mutex;
 };
 
 static struct iommu_ops arm_smmu_ops;
@@ -975,6 +979,7 @@  static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
 		return NULL;
 
 	mutex_init(&smmu_domain->init_mutex);
+	mutex_init(&smmu_domain->reserved_mutex);
 	spin_lock_init(&smmu_domain->pgtbl_lock);
 
 	return &smmu_domain->domain;
@@ -1446,22 +1451,74 @@  out_unlock:
 	return ret;
 }
 
+static int arm_smmu_alloc_reserved_iova_domain(struct iommu_domain *domain,
+					       dma_addr_t iova, size_t size,
+					       unsigned long order)
+{
+	unsigned long granule, mask;
+	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+	int ret = 0;
+
+	granule = 1UL << order;
+	mask = granule - 1;
+	if (iova & mask || (!size) || (size & mask))
+		return -EINVAL;
+
+	if (smmu_domain->reserved_iova_domain)
+		return -EEXIST;
+
+	mutex_lock(&smmu_domain->reserved_mutex);
+
+	smmu_domain->reserved_iova_domain =
+		kzalloc(sizeof(struct iova_domain), GFP_KERNEL);
+	if (!smmu_domain->reserved_iova_domain) {
+		ret = -ENOMEM;
+		goto unlock;
+	}
+
+	init_iova_domain(smmu_domain->reserved_iova_domain,
+			 granule, iova >> order, (iova + size - 1) >> order);
+
+unlock:
+	mutex_unlock(&smmu_domain->reserved_mutex);
+	return ret;
+}
+
+static void arm_smmu_free_reserved_iova_domain(struct iommu_domain *domain)
+{
+	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+	struct iova_domain *iovad = smmu_domain->reserved_iova_domain;
+
+	if (!iovad)
+		return;
+
+	mutex_lock(&smmu_domain->reserved_mutex);
+
+	put_iova_domain(iovad);
+	kfree(iovad);
+
+	mutex_unlock(&smmu_domain->reserved_mutex);
+}
+
 static struct iommu_ops arm_smmu_ops = {
-	.capable		= arm_smmu_capable,
-	.domain_alloc		= arm_smmu_domain_alloc,
-	.domain_free		= arm_smmu_domain_free,
-	.attach_dev		= arm_smmu_attach_dev,
-	.detach_dev		= arm_smmu_detach_dev,
-	.map			= arm_smmu_map,
-	.unmap			= arm_smmu_unmap,
-	.map_sg			= default_iommu_map_sg,
-	.iova_to_phys		= arm_smmu_iova_to_phys,
-	.add_device		= arm_smmu_add_device,
-	.remove_device		= arm_smmu_remove_device,
-	.device_group		= arm_smmu_device_group,
-	.domain_get_attr	= arm_smmu_domain_get_attr,
-	.domain_set_attr	= arm_smmu_domain_set_attr,
-	.pgsize_bitmap		= -1UL, /* Restricted during device attach */
+	.capable			= arm_smmu_capable,
+	.domain_alloc			= arm_smmu_domain_alloc,
+	.domain_free			= arm_smmu_domain_free,
+	.attach_dev			= arm_smmu_attach_dev,
+	.detach_dev			= arm_smmu_detach_dev,
+	.map				= arm_smmu_map,
+	.unmap				= arm_smmu_unmap,
+	.map_sg				= default_iommu_map_sg,
+	.iova_to_phys			= arm_smmu_iova_to_phys,
+	.add_device			= arm_smmu_add_device,
+	.remove_device			= arm_smmu_remove_device,
+	.device_group			= arm_smmu_device_group,
+	.domain_get_attr		= arm_smmu_domain_get_attr,
+	.domain_set_attr		= arm_smmu_domain_set_attr,
+	.alloc_reserved_iova_domain	= arm_smmu_alloc_reserved_iova_domain,
+	.free_reserved_iova_domain	= arm_smmu_free_reserved_iova_domain,
+	/* Page size bitmap, restricted during device attach */
+	.pgsize_bitmap			= -1UL,
 };
 
 static void arm_smmu_device_reset(struct arm_smmu_device *smmu)