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| author | Christoffer Dall <christoffer.dall@linaro.org> | 2016-08-03 18:03:44 +0200 |
|---|---|---|
| committer | Christoffer Dall <christoffer.dall@linaro.org> | 2016-08-15 23:00:20 +0200 |
| commit | d9ae449b3d14d7c55f69af329972f175d180e68d (patch) | |
| tree | c9b04b65130b96654d275cb550568748a4087f08 /virt | |
| parent | 2cccbb368a2bf27d98cf36bb424fbbf5572c0fab (diff) | |
| download | linux-0-day-d9ae449b3d14d7c55f69af329972f175d180e68d.tar.gz linux-0-day-d9ae449b3d14d7c55f69af329972f175d180e68d.tar.xz | |
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')
| -rw-r--r-- | virt/kvm/arm/vgic/vgic-mmio-v3.c | 26 |
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 ff668e0dd586d..90d81811fdda0 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); } /* |