KVM: arm/arm64: vgic-its: Check CBASER/BASER validity before enabling the ITS

The spec says it is UNPREDICTABLE to enable the ITS
if any of the following conditions are true:

- GITS_CBASER.Valid == 0.
- GITS_BASER<n>.Valid == 0, for any GITS_BASER<n> register
  where the Type field indicates Device.
- GITS_BASER<n>.Valid == 0, for any GITS_BASER<n> register
  where the Type field indicates Interrupt Collection and
  GITS_TYPER.HCC == 0.

In that case, let's keep the ITS disabled.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reported-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 6a715a6ec64e..e69ef7d27fde 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -1466,6 +1466,16 @@ static void vgic_mmio_write_its_ctlr(struct kvm *kvm, struct vgic_its *its,
 {
         mutex_lock(&its->cmd_lock);
 
+        /*
+         * It is UNPREDICTABLE to enable the ITS if any of the CBASER or
+         * device/collection BASER are invalid
+         */
+        if (!its->enabled && (val & GITS_CTLR_ENABLE) &&
+                (!(its->baser_device_table & GITS_BASER_VALID) ||
+                 !(its->baser_coll_table & GITS_BASER_VALID) ||
+                 !(its->cbaser & GITS_CBASER_VALID)))
+                goto out;
+
         its->enabled = !!(val & GITS_CTLR_ENABLE);
 
         /*
@@ -1474,6 +1484,7 @@ static void vgic_mmio_write_its_ctlr(struct kvm *kvm, struct vgic_its *its,
          */
         vgic_its_process_commands(kvm, its);
 
+out:
         mutex_unlock(&its->cmd_lock);
 }