> On Aug 1, 2023, at 6:46 PM, Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > On Tue, Aug 01, 2023 at 07:06:57PM +0000, Long Li wrote: > >> The driver interrupt code limits the CPU processing time of each EQ >> by reading a small batch of EQEs in this interrupt. It guarantees >> all the EQs are checked on this CPU, and limits the interrupt >> processing time for any given EQ. In this way, a bad EQ (which is >> stormed by a bad user doing unreasonable re-arming on the CQ) can't >> storm other EQs on this CPU. > > Of course it can, the bad use just creates a million EQs and pushes a > bit of work through them constantly. How is that really any different > from pushing more EQEs into a single EQ? > > And how does your EQ multiplexing work anyhow? Do you poll every EQ on > every interrupt? That itself is a DOS vector. > > Jason User does not create eqs directly . EQ creation is by product of opening device ie allocating context. I am not sure if the same process is allowed to open device multiple times - must be some kind of lock implemented. So million eqs are probably far fetched . As for how the eq servicing is done - only those eq’s for which the interrupt is raised are checked. And each eq is tied only once and only to a single interrupt. Ajay
