Re: blktest/rxe almost working

On 9/2/21 6:38 PM, Jason Gunthorpe wrote:

On Thu, Sep 02, 2021 at 04:41:15PM -0500, Bob Pearson wrote:

quoted

Now that for-next is on 5.14.0-rc6+ blktest srp/002 is very close to
working for rxe but there is still one error. After adding MW
support I added a test to local invalidate to check and see if the
l/rkey matched the key actually contained in the MR/MW when local
invalidate is called. This is failing for srp/002 with the key
portion of the rkey off by one. Looking at ib_srp.c I see code that
does in fact increment the rkey by one and also has code that posts
a local invalidate. This was never checked before and is now failing
to match. If I mask off the key portion in the test the whole test
case passes so the other problems appear to have been fixed. If the
increment and invalidate are out of sync this could result in the
error. I suspect this may be a bug in srp. Worst case I can remove
this test but I would rather not.

I didn't check the spec, but since SRP works with HW devices I wonder
if invalidation is supposed to ignore the variant bits in the mkey?

Jason

I am a little worried. srp is pretty complex but roughly it looks like it maintains a pool of
MRs which it recycles. Each time it reuses the MR it increments the key portion of the rkey. Before
that it uses local invalidate WRs to invalidate the MRs presumably to prevent stray accesses
to the old version of the MR from e.g. replicated packets. It posts these WRs to a send queue but I
don't see where it closes the loop by waiting for a WC so there may be a race between the invalidate
and the subsequent map_sg call. The invalidate marks the MR as not usable so this must all happen
before the MR is turned on again.

Bob