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authorChristoffer Dall <christoffer.dall@linaro.org>2016-08-03 18:03:44 +0200
committerChristoffer Dall <christoffer.dall@linaro.org>2016-08-15 23:00:20 +0200
commitd9ae449b3d14d7c55f69af329972f175d180e68d (patch)
treec9b04b65130b96654d275cb550568748a4087f08 /virt/kvm
parent2cccbb368a2bf27d98cf36bb424fbbf5572c0fab (diff)
downloadlinux-stericsson-d9ae449b3d14d7c55f69af329972f175d180e68d.tar.gz
KVM: arm64: vgic-its: Make updates to propbaser/pendbaser atomic
There are two problems with the current implementation of the MMIO handlers for the propbaser and pendbaser: First, the write to the value itself is not guaranteed to be an atomic 64-bit write so two concurrent writes to the structure field could be intermixed. Second, because we do a read-modify-update operation without any synchronization, if we have two 32-bit accesses to separate parts of the register, we can loose one of them. By using the atomic cmpxchg64 we should cover both issues above. Reviewed-by: Andre Przywara <andre.przywara@arm.com> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Diffstat (limited to 'virt/kvm')
-rw-r--r--virt/kvm/arm/vgic/vgic-mmio-v3.c26
1 files changed, 16 insertions, 10 deletions
diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
index ff668e0dd586..90d81811fdda 100644
--- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
+++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
@@ -306,16 +306,19 @@ static void vgic_mmio_write_propbase(struct kvm_vcpu *vcpu,
{
struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
- u64 propbaser = dist->propbaser;
+ u64 old_propbaser, propbaser;
/* Storing a value with LPIs already enabled is undefined */
if (vgic_cpu->lpis_enabled)
return;
- propbaser = update_64bit_reg(propbaser, addr & 4, len, val);
- propbaser = vgic_sanitise_propbaser(propbaser);
-
- dist->propbaser = propbaser;
+ do {
+ old_propbaser = dist->propbaser;
+ propbaser = old_propbaser;
+ propbaser = update_64bit_reg(propbaser, addr & 4, len, val);
+ propbaser = vgic_sanitise_propbaser(propbaser);
+ } while (cmpxchg64(&dist->propbaser, old_propbaser,
+ propbaser) != old_propbaser);
}
static unsigned long vgic_mmio_read_pendbase(struct kvm_vcpu *vcpu,
@@ -331,16 +334,19 @@ static void vgic_mmio_write_pendbase(struct kvm_vcpu *vcpu,
unsigned long val)
{
struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
- u64 pendbaser = vgic_cpu->pendbaser;
+ u64 old_pendbaser, pendbaser;
/* Storing a value with LPIs already enabled is undefined */
if (vgic_cpu->lpis_enabled)
return;
- pendbaser = update_64bit_reg(pendbaser, addr & 4, len, val);
- pendbaser = vgic_sanitise_pendbaser(pendbaser);
-
- vgic_cpu->pendbaser = pendbaser;
+ do {
+ old_pendbaser = vgic_cpu->pendbaser;
+ pendbaser = old_pendbaser;
+ pendbaser = update_64bit_reg(pendbaser, addr & 4, len, val);
+ pendbaser = vgic_sanitise_pendbaser(pendbaser);
+ } while (cmpxchg64(&vgic_cpu->pendbaser, old_pendbaser,
+ pendbaser) != old_pendbaser);
}
/*