On Fri, Jul 28, 2023 at 05:51:46PM +0000, Long Li wrote:

quoted

Subject: Re: [PATCH v4 1/1] RDMA/mana_ib: Add EQ interrupt support to mana ib
driver.

On Fri, Jul 28, 2023 at 05:07:49PM +0000, Wei Hu wrote:

quoted

Add EQ interrupt support for mana ib driver. Allocate EQs per ucontext
to receive interrupt. Attach EQ when CQ is created. Call CQ interrupt
handler when completion interrupt happens. EQs are destroyed when
ucontext is deallocated.

It seems strange that interrupts would be somehow linked to a ucontext?
interrupts are highly limited, you can DOS the entire system if someone abuses
this.

Generally I expect a properly functioning driver to use one interrupt per CPU core.

Yes, MANA uses one interrupt per CPU. One interrupt is shared among multiple
EQs.

So you have another multiplexing layer between the interrupt and the
EQ? That is alot of multiplexing layers..

quoted

You should tie the CQ to a shared EQ belong to the core that the CQ wants to have
affinity to.

The reason for using a separate EQ for a ucontext, is for preventing DOS. If we use
a shared EQ, a single ucontext can storm this shared EQ affecting
other users.

With a proper design it should not be possible. The CQ adds an entry
to the EQ and that should be rate limited by the ability of userspace
to schedule to re-arm the CQ.

Jason