On 10/21/2016 12:54 AM, Alex Williamson wrote:
> On Tue, 18 Oct 2016 02:52:05 +0530
> Kirti Wankhede <kwankhede@xxxxxxxxxx> wrote:
>
>> Vendor driver using mediated device framework should use
>> vfio_info_add_capability() to add capabilities.
>> Introduced this function to reduce code duplication in vendor drivers.
>>
>> Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx>
>> Signed-off-by: Neo Jia <cjia@xxxxxxxxxx>
>> Change-Id: I6fca329fa2291f37a2c859d0bc97574d9e2ce1a6
>> ---
>> drivers/vfio/vfio.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/vfio.h | 4 +++
>> 2 files changed, 82 insertions(+)
>>
>> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
>> index a5a210005b65..e96cb3f7a23c 100644
>> --- a/drivers/vfio/vfio.c
>> +++ b/drivers/vfio/vfio.c
>> @@ -1799,6 +1799,84 @@ void vfio_info_cap_shift(struct vfio_info_cap *caps, size_t offset)
>> }
>> EXPORT_SYMBOL_GPL(vfio_info_cap_shift);
>>
>> +static int sparse_mmap_cap(struct vfio_info_cap *caps, void *cap_type)
>> +{
>> + struct vfio_info_cap_header *header;
>> + struct vfio_region_info_cap_sparse_mmap *sparse_cap, *sparse = cap_type;
>> + size_t size;
>> +
>> + size = sizeof(*sparse) + sparse->nr_areas * sizeof(*sparse->areas);
>> + header = vfio_info_cap_add(caps, size,
>> + VFIO_REGION_INFO_CAP_SPARSE_MMAP, 1);
>> + if (IS_ERR(header))
>> + return PTR_ERR(header);
>> +
>> + sparse_cap = container_of(header,
>> + struct vfio_region_info_cap_sparse_mmap, header);
>> + sparse_cap->nr_areas = sparse->nr_areas;
>> + memcpy(sparse_cap->areas, sparse->areas,
>> + sparse->nr_areas * sizeof(*sparse->areas));
>> + return 0;
>> +}
>> +
>> +static int region_type_cap(struct vfio_info_cap *caps, void *cap_type)
>> +{
>> + struct vfio_info_cap_header *header;
>> + struct vfio_region_info_cap_type *type_cap, *cap = cap_type;
>> +
>> + header = vfio_info_cap_add(caps, sizeof(*cap),
>> + VFIO_REGION_INFO_CAP_TYPE, 1);
>> + if (IS_ERR(header))
>> + return PTR_ERR(header);
>> +
>> + type_cap = container_of(header, struct vfio_region_info_cap_type,
>> + header);
>> + type_cap->type = cap->type;
>> + type_cap->subtype = cap->subtype;
>> + return 0;
>> +}
>> +
>> +int vfio_info_add_capability(struct vfio_region_info *info,
>> + struct vfio_info_cap *caps,
>> + int cap_type_id,
>> + void *cap_type)
>> +{
>> + int ret;
>> +
>> + if (!cap_type)
>> + return 0;
>> +
>> + switch (cap_type_id) {
>> + case VFIO_REGION_INFO_CAP_SPARSE_MMAP:
>> + ret = sparse_mmap_cap(caps, cap_type);
>> + if (ret)
>> + return ret;
>> + break;
>> +
>> + case VFIO_REGION_INFO_CAP_TYPE:
>> + ret = region_type_cap(caps, cap_type);
>> + if (ret)
>> + return ret;
>> + break;
>> + default:
>> + return -EINVAL;
>> + }
>> +
>> + info->flags |= VFIO_REGION_INFO_FLAG_CAPS;
>> +
>> + if (caps->size) {
>> + if (info->argsz < sizeof(*info) + caps->size) {
>> + info->argsz = sizeof(*info) + caps->size;
>> + info->cap_offset = 0;
>> + } else {
>> + vfio_info_cap_shift(caps, sizeof(*info));
>> + info->cap_offset = sizeof(*info);
>
> This doesn't work. We build the capability chain in a buffer and
> vfio_info_cap_add() expects the chain to be zero-based as each
> capability is added. vfio_info_cap_shift() is meant to be called once
> on that buffer immediately before copying it back to the user buffer to
> adjust the chain offsets to account for the offset within the buffer.
> vfio_info_cap_shift() cannot be called repeatedly on the buffer as we
> do support multiple capabilities in a chain.
>
>From the code I see, we add one type of capability at a time, either
VFIO_REGION_INFO_CAP_SPARSE_MMAP or VFIO_REGION_INFO_CAP_TYPE. Both are
not the part of same case in the switch, right?
I do tested VFIO_REGION_INFO_CAP_SPARSE_MMAP by mapping some part of
BAR0 and that works.
Kirti.
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