On Thu, 2016-12-22 at 07:04 -0800, Steve Wise wrote: > With the addition of the IB/Core drain API, iw_cxgb4 supported drain > by watching the CQs when the QP was out of RTS and signalling "drain > complete" when the last CQE is polled. This, however, doesn't fully > support the drain semantics. Namely, the drain logic is supposed to > signal > "drain complete" only when the application has _processed_ the last > CQE, > not just removed them from the CQ. Thus a small timing hole exists > that > can cause touch after free type bugs in applications using the drain > API > (nvmf, iSER, for example). So iw_cxgb4 needs a better solution. > > The iWARP Verbs spec mandates that "_at some point_ after the QP is > moved to ERROR", the iWARP driver MUST synchronously fail post_send > and > post_recv calls. iw_cxgb4 was currently not allowing any posts once > the > QP is in ERROR. This was in part due to the fact that the HW queues > for > the QP in ERROR state are disabled at this point, so there wasn't > much > else to do but fail the post operation synchronously. This > restriction > is what drove the first drain implementation in iw_cxgb4 that has the > above mentioned flaw. > > This patch changes iw_cxgb4 to allow post_send and post_recv WRs > after > the QP is moved to ERROR state for kernel mode users, thus still > adhering > to the Verbs spec for user mode users, but allowing flush WRs for > kernel > users. Since the HW queues are disabled, we just synthesize a CQE > for > this post, queue it to the SW CQ, and then call the CQ event handler. > This enables proper drain operations for the various storage > applications. > > Signed-off-by: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx> Hi Steve, I've pulled these three patches for 4.10-rc. Thanks. -- Doug Ledford <dledford@xxxxxxxxxx> GPG KeyID: B826A3330E572FDD Key fingerprint = AE6B 1BDA 122B 23B4 265B 1274 B826 A333 0E57 2FDD
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