thr3ads.net - Linux Virtualization - [PATCH v5] iommu/virtio: Use page size bitmap supported by endpoint [May 2020]

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Michael S. Tsirkin

2020-May-06 00:22 UTC

[PATCH v5] iommu/virtio: Use page size bitmap supported by endpoint

On Tue, May 05, 2020 at 03:00:04PM +0530, Bharat Bhushan
wrote:> Different endpoint can support different page size, probe
> endpoint if it supports specific page size otherwise use
> global page sizes.
> 
> Signed-off-by: Bharat Bhushan <bbhushan2 at marvell.com>
> ---
> v4->v5:
>  - Rebase to Linux v5.7-rc4
> 
> v3->v4:
>  - Fix whitespace error
> 
> v2->v3:
>  - Fixed error return for incompatible endpoint
>  - __u64 changed to __le64 in header file
> 
>  drivers/iommu/virtio-iommu.c      | 48 ++++++++++++++++++++++++++++---
>  include/uapi/linux/virtio_iommu.h |  7 +++++
>  2 files changed, 51 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index d5cac4f46ca5..9513d2ab819e 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -78,6 +78,7 @@ struct viommu_endpoint {
>  	struct viommu_dev		*viommu;
>  	struct viommu_domain		*vdomain;
>  	struct list_head		resv_regions;
> +	u64				pgsize_bitmap;
>  };
>  
>  struct viommu_request {
> @@ -415,6 +416,19 @@ static int viommu_replay_mappings(struct viommu_domain
*vdomain)
>  	return ret;
>  }
>  
> +static int viommu_set_pgsize_bitmap(struct viommu_endpoint *vdev,
> +				    struct virtio_iommu_probe_pgsize_mask *mask,
> +				    size_t len)
> +{
> +	u64 pgsize_bitmap = le64_to_cpu(mask->pgsize_bitmap);
> +
> +	if (len < sizeof(*mask))
This is too late to validate length, you have dereferenced it already.
do it before the read pls.
> +		return -EINVAL;
OK but note that guest will then just proceed to ignore the
property. Is that really OK? Wouldn't host want to know?

> +
> +	vdev->pgsize_bitmap = pgsize_bitmap;
what if bitmap is 0? Is that a valid size? I see a bunch of
BUG_ON with that value ...

I also see a bunch of code like e.g. this:

        pg_size = 1UL << __ffs(pgsize_bitmap);

which probably won't DTRT on a 32 bit guest if the bitmap has bits
set in the high word.


> +	return 0;
> +}
> +
>  static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
>  			       struct virtio_iommu_probe_resv_mem *mem,
>  			       size_t len)
> @@ -499,6 +513,9 @@ static int viommu_probe_endpoint(struct viommu_dev
*viommu, struct device *dev)
>  		case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
>  			ret = viommu_add_resv_mem(vdev, (void *)prop, len);
>  			break;
> +		case VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK:
> +			ret = viommu_set_pgsize_bitmap(vdev, (void *)prop, len);
> +			break;
>  		default:
>  			dev_err(dev, "unknown viommu prop 0x%x\n", type);
>  		}
> @@ -630,7 +647,7 @@ static int viommu_domain_finalise(struct
viommu_endpoint *vdev,
>  
>  	vdomain->id		= (unsigned int)ret;
>  
> -	domain->pgsize_bitmap	= viommu->pgsize_bitmap;
> +	domain->pgsize_bitmap	= vdev->pgsize_bitmap;
>  	domain->geometry	= viommu->geometry;
>  
>  	vdomain->map_flags	= viommu->map_flags;
> @@ -654,6 +671,29 @@ static void viommu_domain_free(struct iommu_domain
*domain)
>  	kfree(vdomain);
>  }
>  
> +/*
> + * Check whether the endpoint's capabilities are compatible with other
> + * endpoints in the domain. Report any inconsistency.
> + */
> +static bool viommu_endpoint_is_compatible(struct viommu_endpoint *vdev,
> +					  struct viommu_domain *vdomain)
> +{
> +	struct device *dev = vdev->dev;
> +
> +	if (vdomain->viommu != vdev->viommu) {
> +		dev_err(dev, "cannot attach to foreign vIOMMU\n");
> +		return false;
> +	}
> +
> +	if (vdomain->domain.pgsize_bitmap != vdev->pgsize_bitmap) {
> +		dev_err(dev, "incompatible domain bitmap 0x%lx != 0x%llx\n",
> +			vdomain->domain.pgsize_bitmap, vdev->pgsize_bitmap);
> +		return false;
> +	}
I'm confused by this. So let's assume host supports pages sizes
of 4k, 2M, 1G. It signals this in the properties. Nice.
Now domain supports 4k, 2M and that's all. Why is that a problem?
Just don't use 1G ...

> +
> +	return true;
> +}
> +
>  static int viommu_attach_dev(struct iommu_domain *domain, struct device
*dev)
>  {
>  	int i;
> @@ -670,9 +710,8 @@ static int viommu_attach_dev(struct iommu_domain
*domain, struct device *dev)
>  		 * owns it.
>  		 */
>  		ret = viommu_domain_finalise(vdev, domain);
> -	} else if (vdomain->viommu != vdev->viommu) {
> -		dev_err(dev, "cannot attach to foreign vIOMMU\n");
> -		ret = -EXDEV;
> +	} else if (!viommu_endpoint_is_compatible(vdev, vdomain)) {
> +		ret = -EINVAL;
>  	}
>  	mutex_unlock(&vdomain->mutex);
>  
> @@ -886,6 +925,7 @@ static int viommu_add_device(struct device *dev)
>  
>  	vdev->dev = dev;
>  	vdev->viommu = viommu;
> +	vdev->pgsize_bitmap = viommu->pgsize_bitmap;
>  	INIT_LIST_HEAD(&vdev->resv_regions);
>  	dev_iommu_priv_set(dev, vdev);
>  
> diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
> index 48e3c29223b5..2cced7accc99 100644
> --- a/include/uapi/linux/virtio_iommu.h
> +++ b/include/uapi/linux/virtio_iommu.h
As any virtio UAPI change, you need to copy virtio TC at some point
before this is merged ...
> @@ -111,6 +111,7 @@ struct virtio_iommu_req_unmap {
>  
>  #define VIRTIO_IOMMU_PROBE_T_NONE		0
>  #define VIRTIO_IOMMU_PROBE_T_RESV_MEM		1
> +#define VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK	2
>  
>  #define VIRTIO_IOMMU_PROBE_T_MASK		0xfff
>
Does host need to know that guest will ignore the page size mask?
Maybe we need a feature bit.
  > @@ -119,6 +120,12 @@ struct virtio_iommu_probe_property {
>  	__le16					length;
>  };
>  
> +struct virtio_iommu_probe_pgsize_mask {
> +	struct virtio_iommu_probe_property	head;
> +	__u8					reserved[4];
> +	__le64					pgsize_bitmap;
> +};
> +
This is UAPI. Document the format of pgsize_bitmap please.

>  #define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
>  #define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
>  
> -- 
> 2.17.1

Auger Eric

2020-May-07 12:52 UTC

head link

[PATCH v5] iommu/virtio: Use page size bitmap supported by endpoint

Hi,

On 5/6/20 2:22 AM, Michael S. Tsirkin wrote:> On Tue, May 05, 2020 at 03:00:04PM +0530, Bharat Bhushan wrote:
>> Different endpoint can support different page size, probe
>> endpoint if it supports specific page size otherwise use
>> global page sizes.
>>
>> Signed-off-by: Bharat Bhushan <bbhushan2 at marvell.com>
>> ---
>> v4->v5:
>>  - Rebase to Linux v5.7-rc4
>>
>> v3->v4:
>>  - Fix whitespace error
>>
>> v2->v3:
>>  - Fixed error return for incompatible endpoint
>>  - __u64 changed to __le64 in header file
>>
>>  drivers/iommu/virtio-iommu.c      | 48 ++++++++++++++++++++++++++++---
>>  include/uapi/linux/virtio_iommu.h |  7 +++++
>>  2 files changed, 51 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/iommu/virtio-iommu.c
b/drivers/iommu/virtio-iommu.c
>> index d5cac4f46ca5..9513d2ab819e 100644
>> --- a/drivers/iommu/virtio-iommu.c
>> +++ b/drivers/iommu/virtio-iommu.c
>> @@ -78,6 +78,7 @@ struct viommu_endpoint {
>>  	struct viommu_dev		*viommu;
>>  	struct viommu_domain		*vdomain;
>>  	struct list_head		resv_regions;
>> +	u64				pgsize_bitmap;
>>  };
>>  
>>  struct viommu_request {
>> @@ -415,6 +416,19 @@ static int viommu_replay_mappings(struct
viommu_domain *vdomain)
>>  	return ret;
>>  }
>>  
>> +static int viommu_set_pgsize_bitmap(struct viommu_endpoint *vdev,
>> +				    struct virtio_iommu_probe_pgsize_mask *mask,
>> +				    size_t len)
>> +{
>> +	u64 pgsize_bitmap = le64_to_cpu(mask->pgsize_bitmap);
>> +
>> +	if (len < sizeof(*mask))
> 
> This is too late to validate length, you have dereferenced it already.
> do it before the read pls.
> 
>> +		return -EINVAL;
> 
> OK but note that guest will then just proceed to ignore the
> property. Is that really OK? Wouldn't host want to know?
> 
> 
>> +
>> +	vdev->pgsize_bitmap = pgsize_bitmap;
> 
> what if bitmap is 0? Is that a valid size? I see a bunch of
> BUG_ON with that value ...Indeed [PATCH v2] virtio-iommu: Add PAGE_SIZE_MASK property states
"The device MUST set at least one bit in page_size_mask, describing
the page granularity".

atm if the device returns a null mask the guest hits such BUG_ON()

[    1.841434] kernel BUG at drivers/iommu/iommu.c:653!
[    1.842868] Internal error: Oops - BUG: 0 [#1] SMP
[    1.844261] Modules linked in:
[    1.845161] CPU: 6 PID: 325 Comm: kworker/6:1 Not tainted
5.7.0-rc4-aarch64-guest-bharat-v5+ #196
[    1.847474] Hardware name: linux,dummy-virt (DT)
[    1.848329] Workqueue: events deferred_probe_work_func
[    1.849229] pstate: 60400005 (nZCv daif +PAN -UAO)
[    1.850116] pc : iommu_group_create_direct_mappings.isra.24+0x210/0x228
[    1.851351] lr : iommu_group_add_device+0x108/0x2d0
[    1.852270] sp : ffff800015bef880
[    1.852901] x29: ffff800015bef880 x28: ffff0003cc3dab98
[    1.853897] x27: 0000000000000000 x26: ffff0003cc3dab80
[    1.854894] x25: ffff800011033480 x24: ffff0003cc080948
[    1.855891] x23: ffff8000113f49c8 x22: 0000000000000000
[    1.856887] x21: ffff0003cc3dac00 x20: ffff0003cc080a00
[    1.858440] x19: 0000000000000000 x18: 0000000000000010
[    1.860029] x17: 000000009a468e4c x16: 0000000000300604
[    1.861616] x15: ffffffffffffffff x14: 0720072007200720
[    1.863200] x13: 0720072007200720 x12: 0000000000000020
[    1.864787] x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f
[    1.866373] x9 : ffff8000107de0d8 x8 : 7f7f7f7f7f7f7f7f
[    1.868048] x7 : 39322f392f2f2f2f x6 : 0000000080808080
[    1.869634] x5 : ffff0003cc171000 x4 : ffff0003cc171000
[    1.871218] x3 : ffff8000114aff28 x2 : 0000000000000000
[    1.872802] x1 : ffff0003cb3c60b0 x0 : 0000000000000003
[    1.874383] Call trace:
[    1.875133]  iommu_group_create_direct_mappings.isra.24+0x210/0x228
[    1.876996]  iommu_group_add_device+0x108/0x2d0
[    1.878359]  iommu_group_get_for_dev+0xa0/0x210
[    1.879714]  viommu_add_device+0x128/0x480
[    1.880942]  iommu_probe_device+0x5c/0xd8
[    1.882144]  of_iommu_configure+0x160/0x208
[    1.883535]  of_dma_configure+0xec/0x2b8
[    1.884732]  pci_dma_configure+0x48/0xd0
[    1.885911]  really_probe+0xa0/0x448
[    1.886985]  driver_probe_device+0xe8/0x140
[    1.888253]  __device_attach_driver+0x94/0x120
[    1.889581]  bus_for_each_drv+0x84/0xd8
[    1.890730]  __device_attach+0xe4/0x168
[    1.891879]  device_initial_probe+0x1c/0x28
[    1.893164]  bus_probe_device+0xa4/0xb0
[    1.894311]  deferred_probe_work_func+0xa0/0xf0
[    1.895663]  process_one_work+0x1bc/0x458
[    1.896864]  worker_thread+0x150/0x4f8
[    1.898003]  kthread+0x114/0x118
[    1.898977]  ret_from_fork+0x10/0x18
[    1.900056] Code: d63f0020 b9406be2 17ffffe4 a90573fb (d4210000)
[    1.901872] ---[ end trace 47e5fb5111a3e69b ]---
[    1.903251] Kernel panic - not syncing: Fatal exception
[    1.904809] SMP: stopping secondary CPUs
[    1.906024] Kernel Offset: disabled
[    1.907079] CPU features: 0x084002,22000438
[    1.908332] Memory Limit: none
[    1.909255] ---[ end Kernel panic - not syncing: Fatal exception ]---
Connection closed by foreign host.

Thanks

Eric

> 
> I also see a bunch of code like e.g. this:
> 
>         pg_size = 1UL << __ffs(pgsize_bitmap);
> 
> which probably won't DTRT on a 32 bit guest if the bitmap has bits
> set in the high word.
> 
> 
> 
>> +	return 0;
>> +}
>> +
>>  static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
>>  			       struct virtio_iommu_probe_resv_mem *mem,
>>  			       size_t len)
>> @@ -499,6 +513,9 @@ static int viommu_probe_endpoint(struct viommu_dev
*viommu, struct device *dev)
>>  		case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
>>  			ret = viommu_add_resv_mem(vdev, (void *)prop, len);
>>  			break;
>> +		case VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK:
>> +			ret = viommu_set_pgsize_bitmap(vdev, (void *)prop, len);
>> +			break;
>>  		default:
>>  			dev_err(dev, "unknown viommu prop 0x%x\n", type);
>>  		}
>> @@ -630,7 +647,7 @@ static int viommu_domain_finalise(struct
viommu_endpoint *vdev,
>>  
>>  	vdomain->id		= (unsigned int)ret;
>>  
>> -	domain->pgsize_bitmap	= viommu->pgsize_bitmap;
>> +	domain->pgsize_bitmap	= vdev->pgsize_bitmap;
>>  	domain->geometry	= viommu->geometry;
>>  
>>  	vdomain->map_flags	= viommu->map_flags;
>> @@ -654,6 +671,29 @@ static void viommu_domain_free(struct iommu_domain
*domain)
>>  	kfree(vdomain);
>>  }
>>  
>> +/*
>> + * Check whether the endpoint's capabilities are compatible with
other
>> + * endpoints in the domain. Report any inconsistency.
>> + */
>> +static bool viommu_endpoint_is_compatible(struct viommu_endpoint
*vdev,
>> +					  struct viommu_domain *vdomain)
>> +{
>> +	struct device *dev = vdev->dev;
>> +
>> +	if (vdomain->viommu != vdev->viommu) {
>> +		dev_err(dev, "cannot attach to foreign vIOMMU\n");
>> +		return false;
>> +	}
>> +
>> +	if (vdomain->domain.pgsize_bitmap != vdev->pgsize_bitmap) {
>> +		dev_err(dev, "incompatible domain bitmap 0x%lx !=
0x%llx\n",
>> +			vdomain->domain.pgsize_bitmap, vdev->pgsize_bitmap);
>> +		return false;
>> +	}
> 
> I'm confused by this. So let's assume host supports pages sizes
> of 4k, 2M, 1G. It signals this in the properties. Nice.
> Now domain supports 4k, 2M and that's all. Why is that a problem?
> Just don't use 1G ..>
> 
>> +
>> +	return true;
>> +}
>> +
>>  static int viommu_attach_dev(struct iommu_domain *domain, struct
device *dev)
>>  {
>>  	int i;
>> @@ -670,9 +710,8 @@ static int viommu_attach_dev(struct iommu_domain
*domain, struct device *dev)
>>  		 * owns it.
>>  		 */
>>  		ret = viommu_domain_finalise(vdev, domain);
>> -	} else if (vdomain->viommu != vdev->viommu) {
>> -		dev_err(dev, "cannot attach to foreign vIOMMU\n");
>> -		ret = -EXDEV;
>> +	} else if (!viommu_endpoint_is_compatible(vdev, vdomain)) {
>> +		ret = -EINVAL;
>>  	}
>>  	mutex_unlock(&vdomain->mutex);
>>  
>> @@ -886,6 +925,7 @@ static int viommu_add_device(struct device *dev)
>>  
>>  	vdev->dev = dev;
>>  	vdev->viommu = viommu;
>> +	vdev->pgsize_bitmap = viommu->pgsize_bitmap;
>>  	INIT_LIST_HEAD(&vdev->resv_regions);
>>  	dev_iommu_priv_set(dev, vdev);
>>  
>> diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
>> index 48e3c29223b5..2cced7accc99 100644
>> --- a/include/uapi/linux/virtio_iommu.h
>> +++ b/include/uapi/linux/virtio_iommu.h
> 
> As any virtio UAPI change, you need to copy virtio TC at some point
> before this is merged ...
> 
>> @@ -111,6 +111,7 @@ struct virtio_iommu_req_unmap {
>>  
>>  #define VIRTIO_IOMMU_PROBE_T_NONE		0
>>  #define VIRTIO_IOMMU_PROBE_T_RESV_MEM		1
>> +#define VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK	2
>>  
>>  #define VIRTIO_IOMMU_PROBE_T_MASK		0xfff
>>
> 
> Does host need to know that guest will ignore the page size mask?
> Maybe we need a feature bit.
>   
>> @@ -119,6 +120,12 @@ struct virtio_iommu_probe_property {
>>  	__le16					length;
>>  };
>>  
>> +struct virtio_iommu_probe_pgsize_mask {
>> +	struct virtio_iommu_probe_property	head;
>> +	__u8					reserved[4];
>> +	__le64					pgsize_bitmap;
>> +};
>> +
> 
> This is UAPI. Document the format of pgsize_bitmap please.
> 
> 
>>  #define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
>>  #define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
>>  
>> -- 
>> 2.17.1
>

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