[PATCH v5 7/8] KVM: arm64: vgic-v3: Expose GICR_TYPER.Last for userspace

Eric Auger
2021-04-04T17:24:55Z

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>

---

v4 -> v5:
- redist region list now is sorted by @base
- change the implementation according to Marc's understanding of
the spec
---
arch/arm64/kvm/vgic/vgic-mmio-v3.c | 58 +++++++++++++++++-------------
include/kvm/arm_vgic.h | 1 +
2 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index e1ed0c5a8eaa..03a253785700 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -251,45 +251,52 @@ static void vgic_mmio_write_v3r_ctlr(struct kvm_vcpu *vcpu,
vgic_enable_lpis(vcpu);
}

+static bool vgic_mmio_vcpu_rdist_is_last(struct kvm_vcpu *vcpu)
+{
+ struct vgic_dist *vgic = &vcpu->kvm->arch.vgic;
+ struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+ struct vgic_redist_region *iter, *rdreg = vgic_cpu->rdreg;
+
+ if (!rdreg)
+ return false;
+
+ 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;
+
+ /*
+ * 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_mmio_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;
- gpa_t last_rdist_typer = rdreg->base + GICR_TYPER +
- (rdreg->free_index - 1) * KVM_VGIC_V3_REDIST_SIZE;
u64 value;

value = (u64)(mpidr & GENMASK(23, 0)) << 32;
value |= ((target_vcpu_id & 0xffff) << 8);

- if (addr == last_rdist_typer)
+ if (vgic_has_its(vcpu->kvm))
+ value |= GICR_TYPER_PLPIS;
+
+ if (vgic_mmio_vcpu_rdist_is_last(vcpu))
value |= GICR_TYPER_LAST;
- if (vgic_has_its(vcpu->kvm))
- value |= GICR_TYPER_PLPIS;

return extract_bytes(value, addr & 7, len);
}

-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);
- int target_vcpu_id = vcpu->vcpu_id;
- u64 value;
-
- value = (u64)(mpidr & GENMASK(23, 0)) << 32;
- value |= ((target_vcpu_id & 0xffff) << 8);
-
- if (vgic_has_its(vcpu->kvm))
- value |= GICR_TYPER_PLPIS;
-
- /* reporting of the Last bit is not supported for userspace */
- return extract_bytes(value, addr & 7, len);
-}
-
static unsigned long vgic_mmio_read_v3r_iidr(struct kvm_vcpu *vcpu,
gpa_t addr, unsigned int 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 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;
--
2.26.3