[PATCH 1/1] KVM: PPC: Book3S: Fix server always zero from kvmppc_xive_get_xive()

[Sam Bobroff]

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).

Fixes: 5af50993850a ("KVM: PPC: Book3S HV: Native usage of the XIVE
interrupt controller")
Cc: sta...@vger.kernel.org
Signed-off-by: Sam Bobroff <sam.bobr...@au1.ibm.com>
---
The other obvious way to patch this would be to set state->guest_server in
kvmppc_xive_set_xive() and that does also work because act_server is usually
equal to guest_server.

However, in the cases where guest_server differed from act_server, the guest
would only move IRQs correctly if it got act_server (the CPU actually handling
the interrupt) here. So, that approach seemed better.

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

diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
index 13304622ab1c..bf457843e032 100644
--- a/arch/powerpc/kvm/book3s_xive.c
+++ b/arch/powerpc/kvm/book3s_xive.c
@@ -622,7 +622,7 @@ int kvmppc_xive_get_xive(struct kvm *kvm, u32 irq, u32 
*server,
                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 *xive, long 
irq, u64 addr)
        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_xive *xive, long 
irq, u64 addr)
        /* 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
diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h
index 5938f7644dc1..6ba63f8e8a61 100644
--- a/arch/powerpc/kvm/book3s_xive.h
+++ b/arch/powerpc/kvm/book3s_xive.h
@@ -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 */
 
-- 
2.14.1.4.g334a7be4f