On Tue, Feb 26, 2019 at 01:52:39PM +0100, Paolo Bonzini wrote:

On 25/02/19 11:57, Cédric Le Goater wrote:

quoted

Hello Paolo,

On 2/25/19 4:33 AM, David Gibson wrote:

quoted

On Fri, Feb 22, 2019 at 12:28:35PM +0100, Cédric Le Goater wrote:

quoted

Some KVM devices will want to handle special mappings related to the
underlying HW. For instance, the XIVE interrupt controller of the
POWER9 processor has MMIO pages for thread interrupt management and
for interrupt source control that need to be exposed to the guest when
the OS has the required support.

Signed-off-by: Cédric Le Goater <clg@kaod.org>

Ah, when I suggested mmap() on the base device fd, I hadn't realized
there wasn't a facility for that yet.

Have you discussed this with Paolo?  

Not yet.

quoted

We'll need some core KVM buy in to merge this.

Here is an extension of the KVM device to allow special mappings.
Something we would need for the support of the POWER9 XIVE interrupt 
controller.

There are two MMIOs we need to expose to the guest : 

 1. HW MMIO controlling of the interrupt presenter registers (TIMA)
 2. HW MMIO of the interrupt sources for interrupt management (ESB)

The TIMA could have been exposed with a page offset in the vCPU mapping
but as it only makes sense when the XIVE interrupt mode is active, we 
chose to use directly the KVM device fd for that. Is that ok ? 

An alternate solution is to use a device ioctl to allocate an anon fd
and do the mapping, but that seems like extra fuss for the same result. 

It's okay, it's a natural extension to dev_ops - but thanks for asking
anyway. :)

Ok, cool.

Given that, do you want to merge directly - since this looks sound
enough, even though the rest of the series needs some polish?  Or
would you prefer it to come in via Paulus' tree?

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson