Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

[tomoyo/tomoyo-test1.git] / arch / x86 / kvm / lapic.c

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index a983a16..dcd60b3 100644 (file)
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -376,7 +376,8 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
        struct kvm_vcpu *vcpu;
        unsigned long i;
        u32 max_id = 255; /* enough space for any xAPIC ID */
-       bool xapic_id_mismatch = false;
+       bool xapic_id_mismatch;
+       int r;
 
        /* Read kvm->arch.apic_map_dirty before kvm->arch.apic_map.  */
        if (atomic_read_acquire(&kvm->arch.apic_map_dirty) == CLEAN)
@@ -386,9 +387,14 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
                  "Dirty APIC map without an in-kernel local APIC");
 
        mutex_lock(&kvm->arch.apic_map_lock);
+
+retry:
        /*
-        * Read kvm->arch.apic_map_dirty before kvm->arch.apic_map
-        * (if clean) or the APIC registers (if dirty).
+        * Read kvm->arch.apic_map_dirty before kvm->arch.apic_map (if clean)
+        * or the APIC registers (if dirty).  Note, on retry the map may have
+        * not yet been marked dirty by whatever task changed a vCPU's x2APIC
+        * ID, i.e. the map may still show up as in-progress.  In that case
+        * this task still needs to retry and complete its calculation.
         */
        if (atomic_cmpxchg_acquire(&kvm->arch.apic_map_dirty,
                                   DIRTY, UPDATE_IN_PROGRESS) == CLEAN) {
@@ -397,6 +403,15 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
                return;
        }
 
+       /*
+        * Reset the mismatch flag between attempts so that KVM does the right
+        * thing if a vCPU changes its xAPIC ID, but do NOT reset max_id, i.e.
+        * keep max_id strictly increasing.  Disallowing max_id from shrinking
+        * ensures KVM won't get stuck in an infinite loop, e.g. if the vCPU
+        * with the highest x2APIC ID is toggling its APIC on and off.
+        */
+       xapic_id_mismatch = false;
+
        kvm_for_each_vcpu(i, vcpu, kvm)
                if (kvm_apic_present(vcpu))
                        max_id = max(max_id, kvm_x2apic_id(vcpu->arch.apic));
@@ -415,9 +430,15 @@ void kvm_recalculate_apic_map(struct kvm *kvm)
                if (!kvm_apic_present(vcpu))
                        continue;
 
-               if (kvm_recalculate_phys_map(new, vcpu, &xapic_id_mismatch)) {
+               r = kvm_recalculate_phys_map(new, vcpu, &xapic_id_mismatch);
+               if (r) {
                        kvfree(new);
                        new = NULL;
+                       if (r == -E2BIG) {
+                               cond_resched();
+                               goto retry;
+                       }
+
                        goto out;
                }