KVM: arm/arm64: vgic: Don't rely on the wrong pending table

commit ca185b260951d3b55108c0b95e188682d8a507b7 upstream.

It's possible that two LPIs locate in the same "byte_offset" but target
two different vcpus, where their pending status are indicated by two
different pending tables.  In such a scenario, using last_byte_offset
optimization will lead KVM relying on the wrong pending table entry.
Let us use last_ptr instead, which can be treated as a byte index into
a pending table and also, can be vcpu specific.

Fixes: 280771252c1b ("KVM: arm64: vgic-v3: KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES")
Cc: stable@vger.kernel.org
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20191029071919.177-4-yuzenghui@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index 8b958ed..62a3a2f 100644 (file)
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -375,8 +375,8 @@ retry:
 int vgic_v3_save_pending_tables(struct kvm *kvm)
 {
        struct vgic_dist *dist = &kvm->arch.vgic;
-       int last_byte_offset = -1;
        struct vgic_irq *irq;
+       gpa_t last_ptr = ~(gpa_t)0;
        int ret;
        u8 val;
 
@@ -396,11 +396,11 @@ int vgic_v3_save_pending_tables(struct kvm *kvm)
                bit_nr = irq->intid % BITS_PER_BYTE;
                ptr = pendbase + byte_offset;
 
-               if (byte_offset != last_byte_offset) {
+               if (ptr != last_ptr) {
                        ret = kvm_read_guest_lock(kvm, ptr, &val, 1);
                        if (ret)
                                return ret;
-                       last_byte_offset = byte_offset;
+                       last_ptr = ptr;
                }
 
                stored = val & (1U << bit_nr);