On Tue, Jun 11, 2019 at 11:11:08AM -0400, Tom Talpey wrote: > On 6/11/2019 9:21 AM, Bernard Metzler wrote: > > Hi all, > > > > If enabled for siw, during receive operation, a crc32c over > > header and data is being generated and checked. So far, siw > > was generating that CRC from the content of the just written > > target buffer. What kept me busy last weekend were spurious > > CRC errors, if running qperf. I finally found the application > > is constantly writing the target buffer while data are placed > > concurrently, which sometimes races with the CRC computation > > for that buffer, and yields a broken CRC. > > Well, that's a clear bug in the application, assuming siw has > not yet delivered a send completion for the operation using > the buffer. This is a basic Verbs API contract. May be so, but a kernel driver must not make any assumptions about the content of memory controlled by user. So it is clearly wrong to write data to a user buffer and then read it again to compute a CRC. All the applications touching buffers without waiting for a completion are relying on some extended behavior outside the specification, but they cannot cause the kernel to malfunction and report bogus data integrity errors. Jason
