Re: [PATCH RFC 1/2] RDMA/rxe: don't allow registering !PAGE_SIZE mr

[Zhu Yanjun]

在 2023/10/30 20:40, Jason Gunthorpe 写道:
> On Mon, Oct 30, 2023 at 07:51:41AM +0000, Zhijian Li (Fujitsu) wrote:
> > On 27/10/2023 13:41, Li Zhijian wrote:
> > > mr->page_list only encodes *page without page offset, when
> > > page_size != PAGE_SIZE, we cannot restore the address with a wrong
> > > page_offset.
> > >
> > > Note that this patch will break some ULPs that try to register 4K
> > > MR when PAGE_SIZE is not 4K.
> > > SRP and nvme over RXE is known to be impacted.
> > >
> > > Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx>
> > > ---
> > >    drivers/infiniband/sw/rxe/rxe_mr.c | 6 ++++++
> > >    1 file changed, 6 insertions(+)
> > >
> > > diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
> > > index f54042e9aeb2..61a136ea1d91 100644
> > > --- a/drivers/infiniband/sw/rxe/rxe_mr.c
> > > +++ b/drivers/infiniband/sw/rxe/rxe_mr.c
> > > @@ -234,6 +234,12 @@ int rxe_map_mr_sg(struct ib_mr *ibmr, struct scatterlist *sgl,
> > >    	struct rxe_mr *mr = to_rmr(ibmr);
> > >    	unsigned int page_size = mr_page_size(mr);
> > >    
> > > +	if (page_size != PAGE_SIZE) {
> >
> > It seems this condition is too strict, it should be:
> > 	if (!IS_ALIGNED(page_size, PAGE_SIZE))
> >
> > So that, page_size with (N * PAGE_SIZE) can work as previously.
> > Because the offset(mr.iova & page_mask) will get lost only when !IS_ALIGNED(page_size, PAGE_SIZE)
>
> That makes sense

I read all the discussions very carefully.

Thanks, Greg.

Because RXE only supports PAGE_SIZE, when CONFIG_ARM64_64K_PAGES is 
enabled, the PAGE_SIZE is 64K, when CONFIG_ARM64_64K_PAGES is disabled, 
PAGE_SIZE is 4K.

But NVMe calls ib_map_mr_sg with a fixed size SZ_4K. When 
CONFIG_ARM64_64K_PAGES is enabled, it is still 4K. This is not a problem 
in RXE. This problem is in NVMe.

If this problem in NVMe is not fixed, NVMe still can not use RXE to make 
tests with blktests when CONFIG_ARM64_64K_PAGES is enabled.

This is not a problem in RXE, it should not be fixed in RXE.

Zhu Yanjun

> Jason