Re: [PATCH for-next v2 06/18] RDMA/rxe: Add rxe_add_frag() to rxe_mr.c

Bob Pearson
2022-12-01T05:05:13Z

On 11/30/22 18:41, Jason Gunthorpe wrote:
> On Wed, Nov 30, 2022 at 06:36:56PM -0600, Bob Pearson wrote:
>> I'm not looking at my patch you responded to but the one you posted to replace maps
>> by xarrays.
>
> I see, I botched that part
>
>> The existing rxe driver assumes that if ibmr->type == IB_MR_TYPE_DMA
>> that the iova is just a kernel (virtual) address that is already
>> mapped.
>
> No, it is not correct
>
>> Maybe this is not correct but it has always worked this way. These
>> are heavily used by storage stacks (e.g. Lustre) which always use
>> DMA mr's. Since we don't actually do any DMAs we don't need to setup
>> the iommu for these and just do memcpy's without dealing with pages.
>
> You still should be doing the kmap
>
> Jason

Does this have to do with 32 bit machines? I have always tested on 64 bit machines and
dma mr's are always already mapped.

Bob