x86/vpic: force int output to low when in init mode

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.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/hvm/vpic.c b/xen/arch/x86/hvm/vpic.c
index c1c1de7fd0021ae1ec5696a3e7b1e98745c11e1d..9195155ff03c8b63af68722cf3fa0c45a1976c58 100644 (file)
--- 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 )
     {