linux-kernel - Re: [PATCH] KVM: PPC: Book3S HV: Fix pending_pri value in kvmppc_xive_get

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Message-ID: <1513109890.2303.42.camel@kernel.crashing.org>
Date:   Wed, 13 Dec 2017 07:18:10 +1100
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Laurent Vivier <lvivier@...hat.com>, kvm-ppc@...r.kernel.org
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Paul Mackerras <paulus@...abs.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Cédric Le Goater <clg@...d.org>
Subject: Re: [PATCH] KVM: PPC: Book3S HV: Fix pending_pri value in
 kvmppc_xive_get_icp()

On Tue, 2017-12-12 at 18:23 +0100, Laurent Vivier wrote:
> When we migrate a VM from a POWER8 host (XICS) to a POWER9 host
> (XICS-on-XIVE), we have an error:
> 
> qemu-kvm: Unable to restore KVM interrupt controller state \
>           (0xff000000) for CPU 0: Invalid argument
> 
> This is because kvmppc_xics_set_icp() checks the new state
> is internaly consistent, and especially:
> 
> ...
>    1129         if (xisr == 0) {
>    1130                 if (pending_pri != 0xff)
>    1131                         return -EINVAL;
> ...
> 
> On the other side, kvmppc_xive_get_icp() doesn't set
> neither the pending_pri value, nor the xisr value (set to 0)
> (and kvmppc_xive_set_icp() ignores the pending_pri value)
> 
> As xisr is 0, pending_pri must be set to 0xff.
> 
> Signed-off-by: Laurent Vivier <lvivier@...hat.com>

Acked-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>