On 2023-03-15 5:18 p.m., Jens Axboe wrote:
On 3/15/23 2:38 PM, Jens Axboe wrote:
On 3/15/23 2:07?PM, Helge Deller wrote:
On 3/15/23 21:03, Helge Deller wrote:
Hi Jens,
Thanks for doing those fixes!
On 3/14/23 18:16, Jens Axboe wrote:
One issue that became apparent when running io_uring code on parisc is
that for data shared between the application and the kernel, we must
ensure that it's placed correctly to avoid aliasing issues that render
it useless.
The first patch in this series is from Helge, and ensures that the
SQ/CQ rings are mapped appropriately. This makes io_uring actually work
there.
Patches 2..4 are prep patches for patch 5, which adds a variant of
ring mapped provided buffers that have the kernel allocate the memory
for them and the application mmap() it. This brings these mapped
buffers in line with how the SQ/CQ rings are managed too.
I'm not fully sure if this ONLY impacts archs that set SHM_COLOUR,
of which there is only parisc, or if SHMLBA setting archs (of which
there are others) are impact to any degree as well...
It would be interesting to find out. I'd assume that other arches,
e.g. sparc, might have similiar issues.
Have you tested your patches on other arches as well?
By the way, I've now tested this series on current git head on an
older parisc box (with PA8700 / PCX-W2 CPU).
Results of liburing testsuite:
Tests timed out (1): <send-zerocopy.t> - (may not be a failure)
Tests failed (5): <buf-ring.t> <file-verify.t> <poll-race-mshot.t> <ringbuf-read.t> <send_recvmsg.t>
If you update your liburing git copy, switch to the ring-buf-alloc branch,
then all of the above should work:
With master liburing branch, test/poll-race-mshot.t still crashes my rp3440:
Running test poll-race-mshot.t Bad cqe res -233
Bad cqe res -233
Bad cqe res -233
There is a total lockup with no messages of any kind.
I think the io_uring code needs to reject user supplied ring buffers that are not equivalently mapped
to the corresponding kernel pages. Don't know if it would be possible to reallocate kernel pages so they
are equivalently mapped.
Dave
--
John David Anglin dave.anglin@xxxxxxxx
