[PATCH 4/4] KVM: arm64: vgic-v3: Advertise GICR_CTLR.{IR, CES} as a new GICD_IIDR revision

Marc Zyngier
2022-03-14T16:41:04Z

Since adversising GICR_CTLR.{IC,CES} is directly observable from
a guest, we need to make it selectable from userspace.

For that, bump the default GICD_IIDR revision and let userspace
downgrade it to the previous default. For GICv2, the two distributor
revisions are strictly equivalent.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/kvm/vgic/vgic-init.c | 7 ++++++-
arch/arm64/kvm/vgic/vgic-mmio-v2.c | 18 +++++++++++++++---
arch/arm64/kvm/vgic/vgic-mmio-v3.c | 23 +++++++++++++++++++++--
include/kvm/arm_vgic.h | 3 +++
4 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c
index fc00304fe7d8..f84e04f334c6 100644
--- a/arch/arm64/kvm/vgic/vgic-init.c
+++ b/arch/arm64/kvm/vgic/vgic-init.c
@@ -319,7 +319,12 @@ int vgic_init(struct kvm *kvm)

vgic_debug_init(kvm);

- dist->implementation_rev = 2;
+ /*
+ * If userspace didn't set the GIC implementation revision,
+ * default to the latest and greatest. You know want it.
+ */
+ if (!dist->implementation_rev)
+ dist->implementation_rev = KVM_VGIC_IMP_REV_LATEST;
dist->initialized = true;

out:
diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v2.c b/arch/arm64/kvm/vgic/vgic-mmio-v2.c
index 12e4c223e6b8..f2246c4ca812 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v2.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v2.c
@@ -73,9 +73,13 @@ static int vgic_mmio_uaccess_write_v2_misc(struct kvm_vcpu *vcpu,
gpa_t addr, unsigned int len,
unsigned long val)
{
+ struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
+ u32 reg;
+
switch (addr & 0x0c) {
case GIC_DIST_IIDR:
- if (val != vgic_mmio_read_v2_misc(vcpu, addr, len))
+ reg = vgic_mmio_read_v2_misc(vcpu, addr, len);
+ if ((reg ^ val) & ~GICD_IIDR_REVISION_MASK)
return -EINVAL;

/*
@@ -87,8 +91,16 @@ static int vgic_mmio_uaccess_write_v2_misc(struct kvm_vcpu *vcpu,
* migration from old kernels to new kernels with legacy
* userspace.
*/
- vcpu->kvm->arch.vgic.v2_groups_user_writable = true;
- return 0;
+ reg = FIELD_GET(GICD_IIDR_REVISION_MASK, reg);
+ switch (reg) {
+ case KVM_VGIC_IMP_REV_2:
+ case KVM_VGIC_IMP_REV_3:
+ dist->v2_groups_user_writable = true;
+ dist->implementation_rev = reg;
+ return 0;
+ default:
+ return -EINVAL;
+ }
}

vgic_mmio_write_v2_misc(vcpu, addr, len, val);
diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index a6be403996c6..4c8e4f83e3d1 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -155,13 +155,27 @@ static int vgic_mmio_uaccess_write_v3_misc(struct kvm_vcpu *vcpu,
unsigned long val)
{
struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
+ u32 reg;

switch (addr & 0x0c) {
case GICD_TYPER2:
- case GICD_IIDR:
if (val != vgic_mmio_read_v3_misc(vcpu, addr, len))
return -EINVAL;
return 0;
+ case GICD_IIDR:
+ reg = vgic_mmio_read_v3_misc(vcpu, addr, len);
+ if ((reg ^ val) & ~GICD_IIDR_REVISION_MASK)
+ return -EINVAL;
+
+ reg = FIELD_GET(GICD_IIDR_REVISION_MASK, reg);
+ switch (reg) {
+ case KVM_VGIC_IMP_REV_2:
+ case KVM_VGIC_IMP_REV_3:
+ dist->implementation_rev = reg;
+ return 0;
+ default:
+ return -EINVAL;
+ }
case GICD_CTLR:
/* Not a GICv4.1? No HW SGIs */
if (!kvm_vgic_global_state.has_gicv4_1)
@@ -232,8 +246,13 @@ static unsigned long vgic_mmio_read_v3r_ctlr(struct kvm_vcpu *vcpu,
gpa_t addr, unsigned int len)
{
struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+ unsigned long val;
+
+ val = atomic_read(&vgic_cpu->ctlr);
+ if (vcpu->kvm->arch.vgic.implementation_rev >= KVM_VGIC_IMP_REV_3)
+ val |= GICR_CTLR_IR | GICR_CTLR_CES;

- return vgic_cpu->lpis_enabled ? GICR_CTLR_ENABLE_LPIS : 0;
+ return val;
}

static void vgic_mmio_write_v3r_ctlr(struct kvm_vcpu *vcpu,
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 401236f97cf2..2d8f2e90edc2 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -231,6 +231,9 @@ struct vgic_dist {

/* Implementation revision as reported in the GICD_IIDR */
u32 implementation_rev;
+#define KVM_VGIC_IMP_REV_2 2 /* GICv2 restorable groups */
+#define KVM_VGIC_IMP_REV_3 3 /* GICv3 GICR_CTLR.{IW,CES,RWP} */
+#define KVM_VGIC_IMP_REV_LATEST KVM_VGIC_IMP_REV_3

/* Userspace can write to GICv2 IGROUPR */
bool v2_groups_user_writable;
--
2.34.1