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Subject[PATCH 5/8] KVM: x86: use MDA for interrupt matching
Date
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 APIC MDA in the slow path.
This allows easier reasoning about subsequent matching.

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>
---
arch/x86/kvm/lapic.c | 40 +++++++++++++++++++++++++++++++++-------
1 file changed, 33 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index aae043f38548..871ce6a2485b 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -581,15 +581,24 @@ 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;
+
+ /* XXX: verify that xAPIC accepts 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)
@@ -606,6 +615,7 @@ static bool kvm_apic_match_logical_addr(struct kvm_lapic *apic, u32 mda)
&& (logical_id & mda & 0xffff);

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:
@@ -620,10 +630,26 @@ 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, struct kvm_lapic *ipi, bool x2apic_dest)
+{
+ bool x2apic_mda = ipi ? apic_x2apic_mode(ipi) : x2apic_dest;
+
+ if (!ipi && dest == APIC_BROADCAST)
+ dest = X2APIC_BROADCAST;
+
+ return x2apic_mda ? dest : SET_APIC_DEST_FIELD(dest);
+}
+
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, apic_x2apic_mode(target));

apic_debug("target %p, source %p, dest 0x%x, "
"dest_mode 0x%x, short_hand 0x%x\n",
@@ -633,9 +659,9 @@ 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:
--
2.2.2


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