On Mon, Apr 28, 2014 at 7:27 PM, Alex Williamson
<alex.williamson@xxxxxxxxxx> 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 <a.motakis@xxxxxxxxxxxxxxxxxxxxxx>
>> ---
>> 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
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