[PATCH v3 3/6] x86/vpic: force int output to low when in init mode

[Roger Pau Monne]

When the PIC is on the init sequence prevent interrupt delivery. The
state of the registers is in the process of being set during the init
phase, so it makes sense to prevent any int line changes during that
process.

Requested-by: Jan Beulich <jbeul...@suse.com>
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
---
Changes since v2:
 - New in this version.
---
 xen/arch/x86/hvm/vpic.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/hvm/vpic.c b/xen/arch/x86/hvm/vpic.c
index c1c1de7fd0..9195155ff0 100644
--- a/xen/arch/x86/hvm/vpic.c
+++ b/xen/arch/x86/hvm/vpic.c
@@ -101,11 +101,14 @@ static void vpic_update_int_output(struct hvm_hw_vpic 
*vpic)
     irq = vpic_get_highest_priority_irq(vpic);
     TRACE_3D(TRC_HVM_EMUL_PIC_INT_OUTPUT, vpic->int_output, vpic->is_master,
              irq);
-    if ( vpic->int_output == (irq >= 0) )
+    if ( vpic->int_output == (!vpic->init_state && irq >= 0) )
         return;
 
-    /* INT line transition L->H or H->L. */
-    vpic->int_output = !vpic->int_output;
+    /*
+     * INT line transition L->H or H->L.
+     * Force line status to L when in init mode.
+     */
+    vpic->int_output = !vpic->init_state && !vpic->int_output;
 
     if ( vpic->int_output )
     {
-- 
2.29.2