[PATCH 2/9] KVM: arm/arm64: vgic-its: Always allow clearing GITS_CREADR/CWRITER

[Eric Auger <eric.auger@redhat.com>]

If the GITS_CBASER Size field is 0, which can correspond to a
reset value, the userspace fails to set the GITS_CREADR/CWRITER
offsets to 0. This failure is not justified.

Let's allow this setting which can also correspond to a reset value.

Signed-off-by: Eric Auger <eric.auger@redhat.com>

---

need to CC stable
---
 virt/kvm/arm/vgic/vgic-its.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index fbbc97b..76bed2d 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -1329,7 +1329,7 @@ static void vgic_mmio_write_its_cwriter(struct kvm *kvm, struct vgic_its *its,
 
 	reg = update_64bit_reg(its->cwriter, addr & 7, len, val);
 	reg = ITS_CMD_OFFSET(reg);
-	if (reg >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
+	if (reg && reg >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
 		mutex_unlock(&its->cmd_lock);
 		return;
 	}
@@ -1370,7 +1370,7 @@ static int vgic_mmio_uaccess_write_its_creadr(struct kvm *kvm,
 	}
 
 	cmd_offset = ITS_CMD_OFFSET(val);
-	if (cmd_offset >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
+	if (cmd_offset && cmd_offset >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
 		ret = -EINVAL;
 		goto out;
 	}
-- 
2.5.5