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SubjectRe: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5
Hi, guys,

> We're taking this to the firmware architects at the moment, but they're
> very fond of the idea of reporting the absence of bugs through
> flags, as this could quickly lead to the exhaustion of flag bits. We'll
> the discussion stew for a bit, but if we don't get this flag, we'll have
> resort to the CPU features.

The architects have spoken, and we're getting a capability flag for this.
I'll repost my patch with new autodetection code that doesn't involve
checking the processor version.

> > > Regarding the performance problem, have you checked whether
converting all
> > > your spin_lock_irqsave to spin_lock/spin_lock_irq improves your
> > > on the older machines? Maybe it's already fast enough that way.
> >
> > It does seem that the only places that the hcall_lock is taken also
> > use msleep, so they must always be in process context. So you can
> > safely just use spin_lock(), right?
> As Arnd said, there are hCalls that will never return H_LONG_BUSY_*,
such as
> H_QUERY_PORT and chums, so they will never sleep. The surrounding
> though, are not prepared to be called from interrupt context (GFP_KERNEL
> to mind), so I agree that a simple spin_lock() will suffice. Thanks,
Arnd, for
> pointing this out.

As I pointed out in my earlier mail, there's still an issue with
map_phys_fmr possibly sleeping. Let's keep the irqsave for the time being
and revisit this part once we find a solution to map_phys_fmr.


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