[PATCH v2 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. Emulating the GICR_TYPER.Last bit
still makes sense for architecture compliance.

This patch restores its support (if the redistributor region
was set) while keeping the code safe.

Signed-off-by: Eric Auger <eric.au...@redhat.com>
---
 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 987e366c8000..7ff23c153128 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 3d74f1060bd1..ec621180ef09 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