[Xen-devel] [PATCH] x86/vlapic: Don't reset APIC mode/ID when handling INIT signal

[Chao Gao <chao.gao@xxxxxxxxx>]

According to SDM "ADVANCED PROGRAMMABLE INTERRUPT CONTROLLER (APIC) ->
"EXTENDED XAPIC (X2APIC)" -> "x2APIC State Transitions", the APIC mode
and APIC ID are preserved when handling INIT signal, no matter the
current mode is x2APIC mode or xAPIC. All the other APIC registers are
initialized, exactly like the result of a reset.  This patch
introduces a new function lapic_INIT() and replaces the wrongly used
lapic_reset().

Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
---
HVM guest can't enable x2apic as XENFEAT_hvm_pirqs is exposed to it.
Why we have this restriction? As a consequence, This patch isn't
tested in that case.
---
 xen/arch/x86/hvm/vlapic.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 2653ba8..5f19253 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -83,6 +83,8 @@ static const unsigned int vlapic_lvt_mask[VLAPIC_LVT_NUM] =
     ((vlapic_get_reg(vlapic, APIC_LVTT) & APIC_TIMER_MODE_MASK) \
      == APIC_TIMER_MODE_TSC_DEADLINE)
 
+static void vlapic_INIT(struct vlapic *vlapic);
+
 static int vlapic_find_highest_vector(const void *bitmap)
 {
     const uint32_t *word = bitmap;
@@ -281,7 +283,7 @@ static void vlapic_init_sipi_one(struct vcpu *target, 
uint32_t icr)
         rc = vcpu_reset(target);
         ASSERT(!rc);
         target->fpu_initialised = fpu_initialised;
-        vlapic_reset(vcpu_vlapic(target));
+        vlapic_INIT(vcpu_vlapic(target));
         domain_unlock(target->domain);
         break;
     }
@@ -1237,18 +1239,15 @@ bool_t is_vlapic_lvtpc_enabled(struct vlapic *vlapic)
             !(vlapic_get_reg(vlapic, APIC_LVTPC) & APIC_LVT_MASKED));
 }
 
-/* Reset the VLPAIC back to its power-on/reset state. */
-void vlapic_reset(struct vlapic *vlapic)
+/* VLAPIC handles INIT signal */
+static void vlapic_INIT(struct vlapic *vlapic)
 {
-    struct vcpu *v = vlapic_vcpu(vlapic);
     int i;
 
-    if ( !has_vlapic(v->domain) )
+    if ( !has_vlapic(vlapic_vcpu(vlapic)->domain) )
         return;
 
-    vlapic_set_reg(vlapic, APIC_ID,  (v->vcpu_id * 2) << 24);
     vlapic_set_reg(vlapic, APIC_LVR, VLAPIC_VERSION);
-
     for ( i = 0; i < 8; i++ )
     {
         vlapic_set_reg(vlapic, APIC_IRR + 0x10 * i, 0);
@@ -1262,7 +1261,6 @@ void vlapic_reset(struct vlapic *vlapic)
     vlapic_set_reg(vlapic, APIC_TMICT,   0);
     vlapic_set_reg(vlapic, APIC_TMCCT,   0);
     vlapic_set_tdcr(vlapic, 0);
-
     vlapic_set_reg(vlapic, APIC_DFR, 0xffffffffU);
 
     for ( i = 0; i < VLAPIC_LVT_NUM; i++ )
@@ -1275,6 +1273,18 @@ void vlapic_reset(struct vlapic *vlapic)
     destroy_periodic_time(&vlapic->pt);
 }
 
+/* Reset the VLPAIC back to its power-on/reset state. */
+void vlapic_reset(struct vlapic *vlapic)
+{
+    struct vcpu *v = vlapic_vcpu(vlapic);
+
+    if ( !has_vlapic(v->domain) )
+        return;
+
+    vlapic_set_reg(vlapic, APIC_ID, (v->vcpu_id * 2) << 24);
+    vlapic_INIT(vlapic);
+}
+
 /* rearm the actimer if needed, after a HVM restore */
 static void lapic_rearm(struct vlapic *s)
 {
-- 
1.8.3.1


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