Re: [PATCH] powerpc/xive: store server for masked interrupt in kvmppc_xive_set_xive()

On Fri, Nov 24, 2017 at 07:38:13AM +1100, Benjamin Herrenschmidt wrote:

On Thu, 2017-11-23 at 10:06 +0100, Laurent Vivier wrote:

quoted

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...

So does that amount to a NAK?

quoted

 	/*
 	 * 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.

quoted

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

How do you think this should be fixed?

Laurent, are you reworking the patch at the moment?

Paul.