[PATCH v4 5/8] arm/arm64: KVM: vgic: handle out-of-range MMIO accesses

Marc Zyngier
2014-09-11T11:09:33Z

Now that we can (almost) dynamically size the number of interrupts,
we're facing an interesting issue:

We have to evaluate at runtime whether or not an access hits a valid
register, based on the sizing of this particular instance of the
distributor. Furthermore, the GIC spec says that accessing a reserved
register is RAZ/WI.

For this, add a new field to our range structure, indicating the number
of bits a single interrupts uses. That allows us to find out whether or
not the access is in range.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
include/kvm/arm_vgic.h | 3 ++-
virt/kvm/arm/vgic.c | 56 ++++++++++++++++++++++++++++++++++++++++----------
2 files changed, 47 insertions(+), 12 deletions(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 3900e31..97f5f57 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -32,6 +32,7 @@

#define VGIC_V2_MAX_LRS (1 << 6)
#define VGIC_V3_MAX_LRS 16
+#define VGIC_MAX_IRQS 1024

/* Sanity checks... */
#if (KVM_MAX_VCPUS > 8)
@@ -42,7 +43,7 @@
#error "VGIC_NR_IRQS must be a multiple of 32"
#endif

-#if (VGIC_NR_IRQS > 1024)
+#if (VGIC_NR_IRQS > VGIC_MAX_IRQS)
#error "VGIC_NR_IRQS must be <= 1024"
#endif

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 7e6e64d..ab01cab 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -892,6 +892,7 @@ static bool handle_mmio_sgi_clear(struct kvm_vcpu *vcpu,
struct mmio_range {
phys_addr_t base;
unsigned long len;
+ int bits_per_irq;
bool (*handle_mmio)(struct kvm_vcpu *vcpu, struct kvm_exit_mmio *mmio,
phys_addr_t offset);
};
@@ -900,56 +901,67 @@ static const struct mmio_range vgic_dist_ranges[] = {
{
.base = GIC_DIST_CTRL,
.len = 12,
+ .bits_per_irq = 0,
.handle_mmio = handle_mmio_misc,
},
{
.base = GIC_DIST_IGROUP,
- .len = VGIC_NR_IRQS / 8,
+ .len = VGIC_MAX_IRQS / 8,
+ .bits_per_irq = 1,
.handle_mmio = handle_mmio_raz_wi,
},
{
.base = GIC_DIST_ENABLE_SET,
- .len = VGIC_NR_IRQS / 8,
+ .len = VGIC_MAX_IRQS / 8,
+ .bits_per_irq = 1,
.handle_mmio = handle_mmio_set_enable_reg,
},
{
.base = GIC_DIST_ENABLE_CLEAR,
- .len = VGIC_NR_IRQS / 8,
+ .len = VGIC_MAX_IRQS / 8,
+ .bits_per_irq = 1,
.handle_mmio = handle_mmio_clear_enable_reg,
},
{
.base = GIC_DIST_PENDING_SET,
- .len = VGIC_NR_IRQS / 8,
+ .len = VGIC_MAX_IRQS / 8,
+ .bits_per_irq = 1,
.handle_mmio = handle_mmio_set_pending_reg,
},
{
.base = GIC_DIST_PENDING_CLEAR,
- .len = VGIC_NR_IRQS / 8,
+ .len = VGIC_MAX_IRQS / 8,
+ .bits_per_irq = 1,
.handle_mmio = handle_mmio_clear_pending_reg,
},
{
.base = GIC_DIST_ACTIVE_SET,
- .len = VGIC_NR_IRQS / 8,
+ .len = VGIC_MAX_IRQS / 8,
+ .bits_per_irq = 1,
.handle_mmio = handle_mmio_raz_wi,
},
{
.base = GIC_DIST_ACTIVE_CLEAR,
- .len = VGIC_NR_IRQS / 8,
+ .len = VGIC_MAX_IRQS / 8,
+ .bits_per_irq = 1,
.handle_mmio = handle_mmio_raz_wi,
},
{
.base = GIC_DIST_PRI,
- .len = VGIC_NR_IRQS,
+ .len = VGIC_MAX_IRQS,
+ .bits_per_irq = 8,
.handle_mmio = handle_mmio_priority_reg,
},
{
.base = GIC_DIST_TARGET,
- .len = VGIC_NR_IRQS,
+ .len = VGIC_MAX_IRQS,
+ .bits_per_irq = 8,
.handle_mmio = handle_mmio_target_reg,
},
{
.base = GIC_DIST_CONFIG,
- .len = VGIC_NR_IRQS / 4,
+ .len = VGIC_MAX_IRQS / 4,
+ .bits_per_irq = 2,
.handle_mmio = handle_mmio_cfg_reg,
},
{
@@ -987,6 +999,22 @@ struct mmio_range *find_matching_range(const struct mmio_range *ranges,
return NULL;
}

+static bool vgic_validate_access(const struct vgic_dist *dist,
+ const struct mmio_range *range,
+ unsigned long offset)
+{
+ int irq;
+
+ if (!range->bits_per_irq)
+ return true; /* Not an irq-based access */
+
+ irq = offset * 8 / range->bits_per_irq;
+ if (irq >= dist->nr_irqs)
+ return false;
+
+ return true;
+}
+
/**
* vgic_handle_mmio - handle an in-kernel MMIO access
* @vcpu: pointer to the vcpu performing the access
@@ -1026,7 +1054,13 @@ bool vgic_handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,

spin_lock(&vcpu->kvm->arch.vgic.lock);
offset = mmio->phys_addr - range->base - base;
- updated_state = range->handle_mmio(vcpu, mmio, offset);
+ if (vgic_validate_access(dist, range, offset)) {
+ updated_state = range->handle_mmio(vcpu, mmio, offset);
+ } else {
+ vgic_reg_access(mmio, NULL, offset,
+ ACCESS_READ_RAZ | ACCESS_WRITE_IGNORED);
+ updated_state = false;
+ }
spin_unlock(&vcpu->kvm->arch.vgic.lock);
kvm_prepare_mmio(run, mmio);
kvm_handle_mmio_return(vcpu, run);
--
2.0.4