Re: [RFC PATCH v2 20/22] i386/xen: HVMOP_set_param / HVM_PARAM_CALLBACK_IRQ

[David Woodhouse]

On Mon, 2022-12-12 at 16:16 +0000, Paul Durrant wrote:
> On 09/12/2022 09:56, David Woodhouse wrote:
> > From: Ankur Arora <ankur.a.arora@oracle.com>
> > The HVM_PARAM_CALLBACK_IRQ parameter controls the system-wide event
> > channel upcall method.  The vector support is handled by KVM internally,
> > when the evtchn_upcall_pending field in the vcpu_info is set.
> > The GSI and PCI_INTX delivery methods are not supported. yet; those
> > need to simulate a level-triggered event on the I/OAPIC.
> 
> That's gonna be somewhat limiting if anyone runs a Windows guest with 
> upcall vector support turned off... which is an option at:
> 
> https://xenbits.xen.org/gitweb/?p=pvdrivers/win/xenbus.git;a=blob;f=src/xenbus/evtchn.c;;hb=HEAD#l1928

Sure. And as you know, I also added the 'xen_no_vector_callback' option
to the Linux command line to allow for that mode to be tested with
Linux too: https://git.kernel.org/torvalds/c/b36b0fe96a 

The GSI and PCI_INTX modes will be added in time, but not yet.

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