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SubjectRe: [PATCH] powerpc/xive: store server for masked interrupt in kvmppc_xive_set_xive()
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On Thu, 2017-11-23 at 10:06 +0100, Laurent Vivier wrote:
> This is needed to map kvmppc_xive_set_xive() behavior
> to kvmppc_xics_set_xive().
>
> As we store the server, kvmppc_xive_get_xive() can return
> the good value and we can also allow kvmppc_xive_int_on().
>
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> ---
> arch/powerpc/kvm/book3s_xive.c | 20 ++++++++------------
> 1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
> index bf457843e032..2781b8733038 100644
> --- a/arch/powerpc/kvm/book3s_xive.c
> +++ b/arch/powerpc/kvm/book3s_xive.c
> @@ -584,10 +584,14 @@ int kvmppc_xive_set_xive(struct kvm *kvm, u32 irq, u32 server,
> * we could initialize interrupts with valid default
> */
>
> - if (new_act_prio != MASKED &&
> - (state->act_server != server ||
> - state->act_priority != new_act_prio))
> - rc = xive_target_interrupt(kvm, state, server, new_act_prio);
> + if (state->act_server != server ||
> + state->act_priority != new_act_prio) {
> + if (new_act_prio != MASKED)
> + rc = xive_target_interrupt(kvm, state, server,
> + new_act_prio);
> + if (!rc)
> + state->act_server = server;
> + }

That leads to another problem with this code. My current implementation
is such that is a target queue is full, it will pick another target.
But here, we still update act_server to the passed-in server and
not the actual target...

> /*
> * Perform the final unmasking of the interrupt source
> @@ -646,14 +650,6 @@ int kvmppc_xive_int_on(struct kvm *kvm, u32 irq)
>
> pr_devel("int_on(irq=0x%x)\n", irq);
>
> - /*
> - * Check if interrupt was not targetted
> - */
> - if (state->act_priority == MASKED) {
> - pr_devel("int_on on untargetted interrupt\n");
> - return -EINVAL;
> - }
> -

So my thinking here was that act_priority was never going to be MASKED
except if the interrupt had never been targetted anywhere at machine
startup time. Thus if act_priority is masked, the act_server field
cannot be trusted.

> /* If saved_priority is 0xff, do nothing */
> if (state->saved_priority == MASKED)
> return 0;

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