KVM: x86: use MDA for interrupt matching

In mixed modes, we musn't deliver xAPIC IPIs like x2APIC and vice versa.
Instead of preserving the information in apic_send_ipi(), we regain it
by converting all destinations into correct MDA in the slow path.
This allows easier reasoning about subsequent matching.

Our kvm_apic_broadcast() had an interesting design decision: it didn't
consider IOxAPIC 0xff as broadcast in x2APIC mode ...
everything worked because IOxAPIC can't set that in physical mode and
logical mode considered it as a message for first 8 VCPUs.
This patch interprets IOxAPIC 0xff as x2APIC broadcast.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Message-Id: <1423766494-26150-2-git-send-email-rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 33 insertions, 7 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 44f7b9afbedb..69569744745d 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -588,15 +588,23 @@ static void apic_set_tpr(struct kvm_lapic *apic, u32 tpr)
         apic_update_ppr(apic);
 }
 
-static bool kvm_apic_broadcast(struct kvm_lapic *apic, u32 dest)
+static bool kvm_apic_broadcast(struct kvm_lapic *apic, u32 mda)
 {
-        return dest == (apic_x2apic_mode(apic) ?
-                        X2APIC_BROADCAST : APIC_BROADCAST);
+        if (apic_x2apic_mode(apic))
+                return mda == X2APIC_BROADCAST;
+
+        return GET_APIC_DEST_FIELD(mda) == APIC_BROADCAST;
 }
 
-static bool kvm_apic_match_physical_addr(struct kvm_lapic *apic, u32 dest)
+static bool kvm_apic_match_physical_addr(struct kvm_lapic *apic, u32 mda)
 {
-        return kvm_apic_id(apic) == dest || kvm_apic_broadcast(apic, dest);
+        if (kvm_apic_broadcast(apic, mda))
+                return true;
+
+        if (apic_x2apic_mode(apic))
+                return mda == kvm_apic_id(apic);
+
+        return mda == SET_APIC_DEST_FIELD(kvm_apic_id(apic));
 }
 
 static bool kvm_apic_match_logical_addr(struct kvm_lapic *apic, u32 mda)
@@ -613,6 +621,7 @@ static bool kvm_apic_match_logical_addr(struct kvm_lapic *apic, u32 mda)
                        && (logical_id & mda & 0xffff) != 0;
 
         logical_id = GET_APIC_LOGICAL_ID(logical_id);
+        mda = GET_APIC_DEST_FIELD(mda);
 
         switch (kvm_apic_get_reg(apic, APIC_DFR)) {
         case APIC_DFR_FLAT:
@@ -627,10 +636,27 @@ static bool kvm_apic_match_logical_addr(struct kvm_lapic *apic, u32 mda)
         }
 }
 
+/* KVM APIC implementation has two quirks
+ *  - dest always begins at 0 while xAPIC MDA has offset 24,
+ *  - IOxAPIC messages have to be delivered (directly) to x2APIC.
+ */
+static u32 kvm_apic_mda(unsigned int dest_id, struct kvm_lapic *source,
+                                              struct kvm_lapic *target)
+{
+        bool ipi = source != NULL;
+        bool x2apic_mda = apic_x2apic_mode(ipi ? source : target);
+
+        if (!ipi && dest_id == APIC_BROADCAST && x2apic_mda)
+                return X2APIC_BROADCAST;
+
+        return x2apic_mda ? dest_id : SET_APIC_DEST_FIELD(dest_id);
+}
+
 bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
                            int short_hand, unsigned int dest, int dest_mode)
 {
         struct kvm_lapic *target = vcpu->arch.apic;
+        u32 mda = kvm_apic_mda(dest, source, target);
 
         apic_debug("target %p, source %p, dest 0x%x, "
                    "dest_mode 0x%x, short_hand 0x%x\n",
@@ -640,9 +666,9 @@ bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
         switch (short_hand) {
         case APIC_DEST_NOSHORT:
                 if (dest_mode == APIC_DEST_PHYSICAL)
-                        return kvm_apic_match_physical_addr(target, dest);
+                        return kvm_apic_match_physical_addr(target, mda);
                 else
-                        return kvm_apic_match_logical_addr(target, dest);
+                        return kvm_apic_match_logical_addr(target, mda);
         case APIC_DEST_SELF:
                 return target == source;
         case APIC_DEST_ALLINC: