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SubjectRe: [PATCH v2] vfio iommu: Add dma available capability
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On 9/15/20 5:44 AM, Cornelia Huck wrote:
> On Mon, 14 Sep 2020 18:25:31 -0400
> Matthew Rosato <mjrosato@linux.ibm.com> wrote:
>
>> Commit 492855939bdb ("vfio/type1: Limit DMA mappings per container")
>> added the ability to limit the number of memory backed DMA mappings.
>> However on s390x, when lazy mapping is in use, we use a very large
>> number of concurrent mappings. Let's provide the current allowable
>> number of DMA mappings to userspace via the IOMMU info chain so that
>> userspace can take appropriate mitigation.
>>
>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>> ---
>> drivers/vfio/vfio_iommu_type1.c | 17 +++++++++++++++++
>> include/uapi/linux/vfio.h | 16 ++++++++++++++++
>> 2 files changed, 33 insertions(+)
>
> (...)
>
>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>> index 9204705..a8cc4a5 100644
>> --- a/include/uapi/linux/vfio.h
>> +++ b/include/uapi/linux/vfio.h
>> @@ -1039,6 +1039,22 @@ struct vfio_iommu_type1_info_cap_migration {
>> __u64 max_dirty_bitmap_size; /* in bytes */
>> };
>>
>> +/*
>> + * The DMA available capability allows to report the current number of
>> + * simultaneously outstanding DMA mappings that are allowed.
>> + *
>> + * The structures below define version 1 of this capability.
>
> "The structure below defines..." ?
>

OK

>> + *
>> + * max: specifies the maximum number of outstanding DMA mappings allowed.
>
> I think you forgot to tweak that one:
>
> "avail: specifies the current number of outstanding DMA mappings allowed."
>
> ?

Yep, that's a leftover from v1 :(

>
>> + */
>> +#define VFIO_IOMMU_TYPE1_INFO_DMA_AVAIL 3
>> +
>> +struct vfio_iommu_type1_info_dma_avail {
>> + struct vfio_info_cap_header header;
>> + __u32 avail;
>> +};
>> +
>> +
>> #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
>>
>> /**
>

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