KVM: arm64: vgic-v3: Expose GICR_TYPER.Last for userspace

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

We introduce a new helper, vgic_mmio_vcpu_rdist_is_last() which
computes whether a redistributor is the highest one of a series
of redistributor contributor pages.

With this new implementation we do not need to have a uaccess
read accessor anymore.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210405163941.510258-9-eric.auger@redhat.com

diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index e1ed0c5..03a2537 100644 (file)
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -251,30 +251,35 @@ static void vgic_mmio_write_v3r_ctlr(struct kvm_vcpu *vcpu,
                vgic_enable_lpis(vcpu);
 }
 
-static unsigned long vgic_mmio_read_v3r_typer(struct kvm_vcpu *vcpu,
-                                             gpa_t addr, unsigned int len)
+static bool vgic_mmio_vcpu_rdist_is_last(struct kvm_vcpu *vcpu)
 {
-       unsigned long mpidr = kvm_vcpu_get_mpidr_aff(vcpu);
+       struct vgic_dist *vgic = &vcpu->kvm->arch.vgic;
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
-       struct vgic_redist_region *rdreg = vgic_cpu->rdreg;
-       int target_vcpu_id = vcpu->vcpu_id;
-       gpa_t last_rdist_typer = rdreg->base + GICR_TYPER +
-                       (rdreg->free_index - 1) * KVM_VGIC_V3_REDIST_SIZE;
-       u64 value;
+       struct vgic_redist_region *iter, *rdreg = vgic_cpu->rdreg;
 
-       value = (u64)(mpidr & GENMASK(23, 0)) << 32;
-       value |= ((target_vcpu_id & 0xffff) << 8);
+       if (!rdreg)
+               return false;
 
-       if (addr == last_rdist_typer)
-               value |= GICR_TYPER_LAST;
-       if (vgic_has_its(vcpu->kvm))
-               value |= GICR_TYPER_PLPIS;
+       if (vgic_cpu->rdreg_index < rdreg->free_index - 1) {
+               return false;
+       } else if (rdreg->count && vgic_cpu->rdreg_index == (rdreg->count - 1)) {
+               struct list_head *rd_regions = &vgic->rd_regions;
+               gpa_t end = rdreg->base + rdreg->count * KVM_VGIC_V3_REDIST_SIZE;
 
-       return extract_bytes(value, addr & 7, len);
+               /*
+                * the rdist is the last one of the redist region,
+                * check whether there is no other contiguous rdist region
+                */
+               list_for_each_entry(iter, rd_regions, list) {
+                       if (iter->base == end && iter->free_index > 0)
+                               return false;
+               }
+       }
+       return true;
 }
 
-static unsigned long vgic_uaccess_read_v3r_typer(struct kvm_vcpu *vcpu,
-                                                gpa_t addr, unsigned int len)
+static unsigned long vgic_mmio_read_v3r_typer(struct kvm_vcpu *vcpu,
+                                             gpa_t addr, unsigned int len)
 {
        unsigned long mpidr = kvm_vcpu_get_mpidr_aff(vcpu);
        int target_vcpu_id = vcpu->vcpu_id;
@@ -286,7 +291,9 @@ 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 (vgic_mmio_vcpu_rdist_is_last(vcpu))
+               value |= GICR_TYPER_LAST;
+
        return extract_bytes(value, addr & 7, len);
 }
 
@@ -612,7 +619,7 @@ static const struct vgic_register_region vgic_v3_rd_registers[] = {
                VGIC_ACCESS_32bit),
        REGISTER_DESC_WITH_LENGTH_UACCESS(GICR_TYPER,
                vgic_mmio_read_v3r_typer, vgic_mmio_write_wi,
-               vgic_uaccess_read_v3r_typer, vgic_mmio_uaccess_write_wi, 8,
+               NULL, vgic_mmio_uaccess_write_wi, 8,
                VGIC_ACCESS_64bit | VGIC_ACCESS_32bit),
        REGISTER_DESC_WITH_LENGTH(GICR_WAKER,
                vgic_mmio_read_raz, vgic_mmio_write_wi, 4,
@@ -714,6 +721,7 @@ 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 3d74f10..ec62118 100644 (file)
--- 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;