On Fri, Mar 15, 2019 at 01:06:02PM +0100, Cédric Le Goater wrote:
> The state of the thread interrupt management registers needs to be
> collected for migration. These registers are cached under the
> 'xive_saved_state.w01' field of the VCPU when the VPCU context is
> pulled from the HW thread. An OPAL call retrieves the backup of the
> IPB register in the underlying XIVE NVT structure and merges it in the
> KVM state.
> 
> Signed-off-by: Cédric Le Goater <clg@kaod.org>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

[snip]
> diff --git a/Documentation/virtual/kvm/devices/xive.txt b/Documentation/virtual/kvm/devices/xive.txt
> index e6a984592189..eb864d72ddc3 100644
> --- a/Documentation/virtual/kvm/devices/xive.txt
> +++ b/Documentation/virtual/kvm/devices/xive.txt
> @@ -104,6 +104,25 @@ the legacy interrupt mode, referred as XICS (POWER7/8).
>      -ENOENT: Unknown source number
>      -EINVAL: Not initialized source number
>  
> +* VCPU state
> +
> +  The XIVE IC maintains VP interrupt state in an internal structure
> +  called the NVT. When a VP is not dispatched on a HW processor
> +  thread, this structure can be updated by HW if the VP is the target
> +  of an event notification.
> +
> +  It is important for migration to capture the cached IPB from the NVT
> +  as it synthesizes the priorities of the pending interrupts. We
> +  capture a bit more to report debug information.
> +
> +  KVM_REG_PPC_VP_STATE (4 * 64bits)
> +  bits:     |  63  ....  32  |  31  ....  0  |
> +  values:   |   TIMA word0   |   TIMA word1  |
> +  bits:     | 127       ..........       64  |
> +  values:   |            unused              |
> +  bits:     | 255       ..........      128  |
> +  values:   |            unused              |
> +
>  * Migration:
>  
>    Saving the state of a VM using the XIVE native exploitation mode

Nit: looks like this doc needs to be updated now that only 2x 64-bit
values are returned.

-- 
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