Patch "KVM: PPC: Book3S: Fix server always zero from kvmppc_xive_get_xive()" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

KVM: PPC: Book3S: Fix server always zero from kvmppc_xive_get_xive()

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-ppc-book3s-fix-server-always-zero-from-kvmppc_xive_get_xive.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sam Bobroff <[email protected]>
Date: Tue, 26 Sep 2017 16:47:04 +1000
Subject: KVM: PPC: Book3S: Fix server always zero from kvmppc_xive_get_xive()
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From: Sam Bobroff <[email protected]>

commit 2fb1e946450a4fef74bb72f360555f7760d816f0 upstream.

In KVM's XICS-on-XIVE emulation, kvmppc_xive_get_xive() returns the value of state->guest_server as "server". However, this value is not set by it's counterpart kvmppc_xive_set_xive(). When the guest uses this interface to migrate interrupts away from a CPU that is going offline, it sees all interrupts as belonging to CPU 0, so they are left assigned to (now) offline CPUs.

This patch removes the guest_server field from the state, and returns act_server in it's place (that is, the CPU actually handling the interrupt, which may differ from the one requested).

---
 arch/powerpc/kvm/book3s_xive.c |    5 ++---
 arch/powerpc/kvm/book3s_xive.h |    1 -
 2 files changed, 2 insertions(+), 4 deletions(-)

@@ -622,7 +622,7 @@ int kvmppc_xive_get_xive(struct kvm *kvm
 		return -EINVAL;
 	state = &sb->irq_state[idx];
 	arch_spin_lock(&sb->lock);
-	*server = state->guest_server;
+	*server = state->act_server;
 	*priority = state->guest_priority;
 	arch_spin_unlock(&sb->lock);
 

@@ -1331,7 +1331,7 @@ static int xive_get_source(struct kvmppc
 	xive->saved_src_count++;
 
 	/* Convert saved state into something compatible with xics */
-	val = state->guest_server;
+	val = state->act_server;
 	prio = state->saved_scan_prio;
 
 	if (prio == MASKED) {

@@ -1507,7 +1507,6 @@ static int xive_set_source(struct kvmppc
 	/* First convert prio and mark interrupt as untargetted */
 	act_prio = xive_prio_from_guest(guest_prio);
 	state->act_priority = MASKED;
-	state->guest_server = server;
 
 	/*
 	 * We need to drop the lock due to the mutex below. Hopefully

@@ -35,7 +35,6 @@ struct kvmppc_xive_irq_state {
 	struct xive_irq_data *pt_data;	/* XIVE Pass-through associated data */
 
 	/* Targetting as set by guest */
-	u32 guest_server;		/* Current guest selected target */
 	u8 guest_priority;		/* Guest set priority */
 	u8 saved_priority;		/* Saved priority when masking */
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/kvm-ppc-book3s-fix-server-always-zero-from-kvmppc_xive_get_xive.patch