Re: [EXTERNAL] Re: [RFC PATCH v1] powerpc/prom_init: disable XIVE in Secure VM.

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  4) I'm guessing the problem with XIVE in SVM mode is that XIVE needs
     to write to event queues in guest memory, which would have to be
     explicitly shared for secure mode.  That's true whether it's KVM
     or qemu accessing the guest memory, so kernel_irqchip=on/off is
     entirely irrelevant.

This problem should be already fixed.
The XIVE event queues are shared 

 	
Yes i have a patch for the guest kernel that shares the event 
queue page with the hypervisor. This is done using the
UV_SHARE_PAGE ultracall. This patch is not sent out to any any mailing
lists yet. However the patch by itself does not solve the xive problem
for secure VM.

yes because you also need to share the XIVE TIMA and ESB pages mapped 
in xive_native_esb_fault() and xive_native_tima_fault(). 

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and the remaining problem with XIVE is the KVM page fault handler 
populating the TIMA and ESB pages. Ultravisor doesn't seem to support
this feature and this breaks interrupt management in the guest. 

Yes. This is the bigger issue that needs to be fixed. When the secure guest
accesses the page associated with the xive memslot, a page fault is
generated, which the ultravisor reflects to the hypervisor. Hypervisor
seems to be mapping Hardware-page to that GPA. Unforatunately it is not
informing the ultravisor of that map.  I am trying to understand the
root cause. But since I am not sure what more issues I might run into
after chasing down that issue, I figured its better to disable xive
support in SVM in the interim.

Is it possible to call uv_share_page() from the hypervisor ? 

**** BTW: I figured, I dont need this intermin patch to disable xive for
secure VM.  Just doing "svm=on xive=off" on the kernel command line is
sufficient for now. *****

Yes. 

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But, kernel_irqchip=off should work out of the box. It seems it doesn't. 
Something to investigate.

Dont know why. 

We need to understand why. 

You still need the patch to share the event queue page allocated by the 
guest OS because QEMU will enqueue events. But you should not need anything
else.

Does this option, disable the chip from interrupting the
guest directly; instead mediates the interrupt through the hypervisor?

Yes. The KVM backend is unused, the XIVE interrupt controller is deactivated
for the guest and QEMU notifies the vCPUs directly.  

The TIMA and ESB pages belong the QEMU process and the guest OS will do 
some load and store operations onto them for interrupt management. Is that 
OK from a UV perspective ?  

Thanks,

C.