2014-04-28 15:58:46

by Antonios Motakis

Subject: [RFC PATCH v5 08/11] VFIO_PLATFORM: Support MMAP of MMIO regions

Allow to memory map the MMIO regions of the device so userspace can
directly access them.

Signed-off-by: Antonios Motakis <[email protected]>
---
drivers/vfio/platform/vfio_platform.c | 40 ++++++++++++++++++++++++++++++++++-
1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c
index 7c01ced..37beff3 100644
--- a/drivers/vfio/platform/vfio_platform.c
+++ b/drivers/vfio/platform/vfio_platform.c
@@ -58,6 +58,11 @@ static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
region.flags = VFIO_REGION_INFO_FLAG_READ
| VFIO_REGION_INFO_FLAG_WRITE;

+ /* Only regions addressed with PAGE granularity can be MMAPed
+ * securely. */
+ if (!(region.addr & ~PAGE_MASK) && !(region.size & ~PAGE_MASK))
+ region.flags |= VFIO_REGION_INFO_FLAG_MMAP;
+
vdev->region[i] = region;
}

@@ -268,7 +273,40 @@ err:

static int vfio_platform_mmap(void *device_data, struct vm_area_struct *vma)
{
- return -EINVAL;
+ struct vfio_platform_device *vdev = device_data;
+ unsigned int index;
+ u64 req_len, pgoff, req_start;
+ struct vfio_platform_region region;
+
+ index = vma->vm_pgoff >> (VFIO_PLATFORM_OFFSET_SHIFT - PAGE_SHIFT);
+
+ if (vma->vm_end < vma->vm_start)
+ return -EINVAL;
+ if ((vma->vm_flags & VM_SHARED) == 0)
+ return -EINVAL;
+ if (index >= vdev->num_regions)
+ return -EINVAL;
+ if (vma->vm_start & ~PAGE_MASK)
+ return -EINVAL;
+ if (vma->vm_end & ~PAGE_MASK)
+ return -EINVAL;
+
+ region = vdev->region[index];
+
+ req_len = vma->vm_end - vma->vm_start;
+ pgoff = vma->vm_pgoff &
+ ((1U << (VFIO_PLATFORM_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
+ req_start = pgoff << PAGE_SHIFT;
+
+ if (region.size < PAGE_SIZE || req_start + req_len > region.size)
+ return -EINVAL;
+
+ vma->vm_private_data = vdev;
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+ vma->vm_pgoff = (region.addr >> PAGE_SHIFT) + pgoff;
+
+ return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
+ req_len, vma->vm_page_prot);
}

static const struct vfio_device_ops vfio_platform_ops = {
--
1.8.3.2

2014-04-28 19:42:44

by Alex Williamson

Subject: Re: [RFC PATCH v5 08/11] VFIO_PLATFORM: Support MMAP of MMIO regions

On Mon, 2014-04-28 at 17:52 +0200, Antonios Motakis wrote:
> Allow to memory map the MMIO regions of the device so userspace can
> directly access them.
>
> Signed-off-by: Antonios Motakis <[email protected]>
> ---
> drivers/vfio/platform/vfio_platform.c | 40 ++++++++++++++++++++++++++++++++++-
> 1 file changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c
> index 7c01ced..37beff3 100644
> --- a/drivers/vfio/platform/vfio_platform.c
> +++ b/drivers/vfio/platform/vfio_platform.c
> @@ -58,6 +58,11 @@ static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
> region.flags = VFIO_REGION_INFO_FLAG_READ
> | VFIO_REGION_INFO_FLAG_WRITE;
>
> + /* Only regions addressed with PAGE granularity can be MMAPed
> + * securely. */
> + if (!(region.addr & ~PAGE_MASK) && !(region.size & ~PAGE_MASK))
> + region.flags |= VFIO_REGION_INFO_FLAG_MMAP;
> +

Ok, so the security is only that we need page alignment. Maybe that
could be made more clear in the previous patch. PCI has regions like
the MSI-X table that we need to protect from userspace access beyond
page alignment requirements. Thanks,

Alex

> vdev->region[i] = region;
> }
>
> @@ -268,7 +273,40 @@ err:
>
> static int vfio_platform_mmap(void *device_data, struct vm_area_struct *vma)
> {
> - return -EINVAL;
> + struct vfio_platform_device *vdev = device_data;
> + unsigned int index;
> + u64 req_len, pgoff, req_start;
> + struct vfio_platform_region region;
> +
> + index = vma->vm_pgoff >> (VFIO_PLATFORM_OFFSET_SHIFT - PAGE_SHIFT);
> +
> + if (vma->vm_end < vma->vm_start)
> + return -EINVAL;
> + if ((vma->vm_flags & VM_SHARED) == 0)
> + return -EINVAL;
> + if (index >= vdev->num_regions)
> + return -EINVAL;
> + if (vma->vm_start & ~PAGE_MASK)
> + return -EINVAL;
> + if (vma->vm_end & ~PAGE_MASK)
> + return -EINVAL;
> +
> + region = vdev->region[index];
> +
> + req_len = vma->vm_end - vma->vm_start;
> + pgoff = vma->vm_pgoff &
> + ((1U << (VFIO_PLATFORM_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
> + req_start = pgoff << PAGE_SHIFT;
> +
> + if (region.size < PAGE_SIZE || req_start + req_len > region.size)
> + return -EINVAL;
> +
> + vma->vm_private_data = vdev;
> + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> + vma->vm_pgoff = (region.addr >> PAGE_SHIFT) + pgoff;
> +
> + return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
> + req_len, vma->vm_page_prot);
> }
>
> static const struct vfio_device_ops vfio_platform_ops = {

2014-04-29 13:29:14

by Antonios Motakis

Subject: Re: [RFC PATCH v5 08/11] VFIO_PLATFORM: Support MMAP of MMIO regions

On Mon, Apr 28, 2014 at 7:27 PM, Alex Williamson
<[email protected]> wrote:
> On Mon, 2014-04-28 at 17:52 +0200, Antonios Motakis wrote:
>> Allow to memory map the MMIO regions of the device so userspace can
>> directly access them.
>>
>> Signed-off-by: Antonios Motakis <[email protected]>
>> ---
>> drivers/vfio/platform/vfio_platform.c | 40 ++++++++++++++++++++++++++++++++++-
>> 1 file changed, 39 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c
>> index 7c01ced..37beff3 100644
>> --- a/drivers/vfio/platform/vfio_platform.c
>> +++ b/drivers/vfio/platform/vfio_platform.c
>> @@ -58,6 +58,11 @@ static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
>> region.flags = VFIO_REGION_INFO_FLAG_READ
>> | VFIO_REGION_INFO_FLAG_WRITE;
>>
>> + /* Only regions addressed with PAGE granularity can be MMAPed
>> + * securely. */
>> + if (!(region.addr & ~PAGE_MASK) && !(region.size & ~PAGE_MASK))
>> + region.flags |= VFIO_REGION_INFO_FLAG_MMAP;
>> +
>
> Ok, so the security is only that we need page alignment. Maybe that
> could be made more clear in the previous patch. PCI has regions like
> the MSI-X table that we need to protect from userspace access beyond
> page alignment requirements. Thanks,

Ack, I will make the previous description more clear.

>
> Alex
>
>> vdev->region[i] = region;
>> }
>>
>> @@ -268,7 +273,40 @@ err:
>>
>> static int vfio_platform_mmap(void *device_data, struct vm_area_struct *vma)
>> {
>> - return -EINVAL;
>> + struct vfio_platform_device *vdev = device_data;
>> + unsigned int index;
>> + u64 req_len, pgoff, req_start;
>> + struct vfio_platform_region region;
>> +
>> + index = vma->vm_pgoff >> (VFIO_PLATFORM_OFFSET_SHIFT - PAGE_SHIFT);
>> +
>> + if (vma->vm_end < vma->vm_start)
>> + return -EINVAL;
>> + if ((vma->vm_flags & VM_SHARED) == 0)
>> + return -EINVAL;
>> + if (index >= vdev->num_regions)
>> + return -EINVAL;
>> + if (vma->vm_start & ~PAGE_MASK)
>> + return -EINVAL;
>> + if (vma->vm_end & ~PAGE_MASK)
>> + return -EINVAL;
>> +
>> + region = vdev->region[index];
>> +
>> + req_len = vma->vm_end - vma->vm_start;
>> + pgoff = vma->vm_pgoff &
>> + ((1U << (VFIO_PLATFORM_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
>> + req_start = pgoff << PAGE_SHIFT;
>> +
>> + if (region.size < PAGE_SIZE || req_start + req_len > region.size)
>> + return -EINVAL;
>> +
>> + vma->vm_private_data = vdev;
>> + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>> + vma->vm_pgoff = (region.addr >> PAGE_SHIFT) + pgoff;
>> +
>> + return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
>> + req_len, vma->vm_page_prot);
>> }
>>
>> static const struct vfio_device_ops vfio_platform_ops = {
>
>
>



--
Antonios Motakis
Virtual Open Systems