[PATCH v4 27/32] cxlflash: Fix to prevent stale AFU RRQ

Matthew R. Ochs mrochs at linux.vnet.ibm.com
Wed Sep 30 06:22:39 AEST 2015

> On Sep 28, 2015, at 8:36 PM, Daniel Axtens <dja at axtens.net> wrote:
> Hash: SHA512
> "Matthew R. Ochs" <mrochs at linux.vnet.ibm.com> writes:
>> Following an adapter reset, the AFU RRQ that resides in host memory
>> holds stale data. This can lead to a condition where the RRQ interrupt
>> handler tries to process stale entries and/or endlessly loops due to an
>> out of sync generation bit.
>> To fix, the AFU RRQ in host memory needs to be cleared after each reset.
> This looks good. Do you need anything to bail out of cxlflash_rrq_irq if
> the data goes stale or to all Fs while that function is running?

We're not performing an MMIO here, so I'm not sure how the all Fs check
would apply. We're also protected fairly well by the generation bit. I suppose
we could look at adding some type of 'max iterations' count to protect against
a runaway handler but that would be in a future patch.

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