Re: [PATCH RFC 02/11] iommu: Add iommu_domain type for SVA

Lu Baolu
2022-03-22T00:54:13Z

On 2022/3/21 19:47, Jason Gunthorpe wrote:
> On Sun, Mar 20, 2022 at 02:40:21PM +0800, Lu Baolu wrote:
>> Add a new iommu domain type IOMMU_DOMAIN_SVA to represent an I/O page
>> table which is shared from CPU host VA. Add a sva_cookie field in the
>> iommu_domain structure to save the mm_struct which represent the CPU
>> memory page table.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
>> include/linux/iommu.h | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index 36f43af0af53..3e179b853380 100644
>> +++ b/include/linux/iommu.h
>> @@ -64,6 +64,9 @@ struct iommu_domain_geometry {
>> #define __IOMMU_DOMAIN_PT (1U << 2) /* Domain is identity mapped */
>> #define __IOMMU_DOMAIN_DMA_FQ (1U << 3) /* DMA-API uses flush queue */
>>
>> +#define __IOMMU_DOMAIN_SHARED (1U << 4) /* Page table shared from CPU */
>> +#define __IOMMU_DOMAIN_HOST_VA (1U << 5) /* Host CPU virtual address */
>> +
>> /*
>> * This are the possible domain-types
>> *
>> @@ -86,6 +89,8 @@ struct iommu_domain_geometry {
>> #define IOMMU_DOMAIN_DMA_FQ (__IOMMU_DOMAIN_PAGING | \
>> __IOMMU_DOMAIN_DMA_API | \
>> __IOMMU_DOMAIN_DMA_FQ)
>> +#define IOMMU_DOMAIN_SVA (__IOMMU_DOMAIN_SHARED | \
>> + __IOMMU_DOMAIN_HOST_VA)
>
> Is there any use for this in the core code? I feel like flags should
> only be created if the core code needs to test them in some way.

flags are some attributes of the domain and the combination of multiple
flags forms a domain type.

>
>> @@ -95,6 +100,7 @@ struct iommu_domain {
>> void *handler_token;
>> struct iommu_domain_geometry geometry;
>> struct iommu_dma_cookie *iova_cookie;
>> + struct mm_struct *sva_cookie;
>
> Don't call a mm_struct a cookie please

Sure.

>
> And why do we need this in core code?

Need to connect an SVA domain with mm.

Best regards,
baolu