[PATCH 8/9] KVM: arm64: vgic-v3: Expose GICR_TYPER.Last for userspace

[Eric Auger]

Commit 23bde34771f1 ("KVM: arm64: vgic-v3: Drop the
reporting of GICR_TYPER.Last for userspace") temporarily fixed
a bug identified when attempting to access the GICR_TYPER
register before the redistributor region setting but dropped
the support of the LAST bit. This patch restores its
support (if the redistributor region was set) while keeping the
code safe.

Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
---
 arch/arm64/kvm/vgic/vgic-mmio-v3.c | 7 ++++++-
 include/kvm/arm_vgic.h             | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index 581f0f490000..2f9ef6058f6e 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -277,6 +277,8 @@ static unsigned long vgic_uaccess_read_v3r_typer(struct kvm_vcpu *vcpu,
 						 gpa_t addr, unsigned int len)
 {
 	unsigned long mpidr = kvm_vcpu_get_mpidr_aff(vcpu);
+	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+	struct vgic_redist_region *rdreg = vgic_cpu->rdreg;
 	int target_vcpu_id = vcpu->vcpu_id;
 	u64 value;
 
@@ -286,7 +288,9 @@ static unsigned long vgic_uaccess_read_v3r_typer(struct kvm_vcpu *vcpu,
 	if (vgic_has_its(vcpu->kvm))
 		value |= GICR_TYPER_PLPIS;
 
-	/* reporting of the Last bit is not supported for userspace */
+	if (rdreg && (vgic_cpu->rdreg_index == (rdreg->free_index - 1)))
+		value |= GICR_TYPER_LAST;
+
 	return extract_bytes(value, addr & 7, len);
 }
 
@@ -714,6 +718,7 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu)
 		return -EINVAL;
 
 	vgic_cpu->rdreg = rdreg;
+	vgic_cpu->rdreg_index = rdreg->free_index;
 
 	rd_base = rdreg->base + rdreg->free_index * KVM_VGIC_V3_REDIST_SIZE;
 
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index a8d8fdcd3723..596c069263a7 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -322,6 +322,7 @@ struct vgic_cpu {
 	 */
 	struct vgic_io_device	rd_iodev;
 	struct vgic_redist_region *rdreg;
+	u32 rdreg_index;
 
 	/* Contains the attributes and gpa of the LPI pending tables. */
 	u64 pendbaser;
-- 
2.21.3