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Re: [PATCH V1 03/16] xen/ioreq: Make x86's hvm_ioreq_needs_completion() common



Hi,

On 14/09/2020 15:59, Jan Beulich wrote:
On 10.09.2020 22:21, Oleksandr Tyshchenko wrote:
--- a/xen/include/xen/ioreq.h
+++ b/xen/include/xen/ioreq.h
@@ -35,6 +35,13 @@ static inline struct hvm_ioreq_server 
*get_ioreq_server(const struct domain *d,
      return GET_IOREQ_SERVER(d, id);
  }
+static inline bool hvm_ioreq_needs_completion(const ioreq_t *ioreq)
+{
+    return ioreq->state == STATE_IOREQ_READY &&
+           !ioreq->data_is_ptr &&
+           (ioreq->type != IOREQ_TYPE_PIO || ioreq->dir != IOREQ_WRITE);
+}

While the PIO aspect has been discussed to some length, what about
the data_is_ptr concept? I didn't think there were Arm insns fitting
this? Instead I thought some other Arm-specific adjustments to the
protocol might be needed. At which point the question of course would
be in how far ioreq_t as a whole really fits Arm in its current shape.

I would rather not try to re-invent ioreq_t for Arm if we don't need to. This is only going to increase the amount of arch specific code in a device emulator that really ought to be agnostic.

At the moment, I think it is fine to have "unused" field on Arm as long as they contain the right value.

So I would rather keep the check in common code as well.

Cheers,

--
Julien Grall



 


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