Messages in this thread | | | Subject | Re: [RFC PATCH v4 0/2] RDMA/rxe: Add dma-buf support | From | Christian König <> | Date | Fri, 10 Dec 2021 13:47:37 +0100 |
| |
Am 10.12.21 um 13:42 schrieb Jason Gunthorpe: > On Fri, Dec 10, 2021 at 08:29:24PM +0900, Shunsuke Mie wrote: >> Hi Jason, >> Thank you for replying. >> >> 2021年12月8日(水) 2:14 Jason Gunthorpe <jgg@ziepe.ca>: >>> On Fri, Dec 03, 2021 at 12:51:44PM +0900, Shunsuke Mie wrote: >>>> Hi maintainers, >>>> >>>> Could you please review this patch series? >>> Why is it RFC? >>> >>> I'm confused why this is useful? >>> >>> This can't do copy from MMIO memory, so it shouldn't be compatible >>> with things like Gaudi - does something prevent this? >> I think if an export of the dma-buf supports vmap, CPU is able to access the >> mmio memory. >> >> Is it wrong? If this is wrong, there is no advantages this changes.. > I don't know what the dmabuf folks did, but yes, it is wrong. > > IOMEM must be touched using only special accessors, some platforms > crash if you don't do this. Even x86 will crash if you touch it with > something like an XMM optimized memcpy. > > Christian? If the vmap succeeds what rules must the caller use to > access the memory?
See dma-buf-map.h and especially struct dma_buf_map.
MMIO memory is perfectly supported here and actually the most common case.
Christian.
> > Jason
| |