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Re: [Xen-devel] [PATCH RFC] xen/evtchn: Implement EVTCHNOP_send_imm as a companian to EVTCHNOP_send

On 07/13/2017 09:50 AM, Andrew Cooper wrote:
The event channel ABI passes a pointer to a subop-specific structure.  Some of
these structures however are smaller than the pointers passed in the ABI;
EVTCHNOP_send specifically passes a 4 byte evtchn port, using a 4 or 8 byte

For translated guests (x86 HVM and all ARM), passing the port number directly
avoids a guest pagetable walk, which can be very expensive for Xen to perform.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

I'm absolutely in favor of the approach.

Could we please discuss which hypercalls should offer an immediate
variant before implementing one after the other? I believe those should
all be introduced at the same time in order to make deciding which
variant to use in domU easier: I don't want to have a boolean for each
possible hypercall, but just one.


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