Re: [PATCH 08/19] KVM: PPC: Book3S HV: add a VC_BASE control to the XIVE native device

On Wed, Jan 23, 2019 at 05:56:26PM +0100, Cédric Le Goater wrote:

On 1/22/19 6:14 AM, Paul Mackerras wrote:

quoted

On Mon, Jan 07, 2019 at 07:43:20PM +0100, Cédric Le Goater wrote:

quoted

The ESB MMIO region controls the interrupt sources of the guest. QEMU
will query an fd (GET_ESB_FD ioctl) and map this region at a specific
address for the guest to use. The guest will obtain this information
using the H_INT_GET_SOURCE_INFO hcall. To inform KVM of the address
setting used by QEMU, add a VC_BASE control to the KVM XIVE device

This needs a little more explanation.  I *think* the only way this
gets used is that it gets returned to the guest by the new
hypercalls.  If that is indeed the case it would be useful to mention
that in the patch description, because otherwise taking a value that
userspace provides and which looks like it is an address, and not
doing any validation on it, looks a bit scary.

I think we have solved this problem in another email thread. 

The H_INT_GET_SOURCE_INFO hcall does not need to be implemented in KVM
as all the source information should already be available in QEMU. In
that case, there is no need to inform KVM of where the ESB pages are 
mapped in the guest address space. So we don't need that extra control
on the KVM device. This is good news.

Ah, good to hear.  I thought this looked strange.


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