Re: [PATCH v5 08/10] KVM: arm/arm64: vgic-its: Free caches when GITS_BASER Valid bit is cleared

Marc Zyngier
2017-10-25T10:22:01Z

On Mon, Oct 23 2017 at 4:08:27 pm BST, Eric Auger <eric.auger@redhat.com> wrote:
> When the GITS_BASER<n>.Valid gets cleared, the data structures in
> guest RAM are not valid anymore. The device, collection
> and LPI lists stored in the in-kernel ITS represent the same
> information in some form of cache. So let's void the cache.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
> v4 -> v5:
> - add comment about locking
>
> v2 -> v3:
> - add a comment and clear cache in if block
> ---
> virt/kvm/arm/vgic/vgic-its.c | 27 +++++++++++++++++++++++----
> 1 file changed, 23 insertions(+), 4 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 8098f91..bdfceb4 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1434,8 +1434,9 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
> unsigned long val)
> {
> const struct vgic_its_abi *abi = vgic_its_get_abi(its);
> - u64 entry_size, device_type;
> + u64 entry_size;
> u64 reg, *regptr, clearbits = 0;
> + int type;
>
> /* When GITS_CTLR.Enable is 1, we ignore write accesses. */
> if (its->enabled)
> @@ -1445,12 +1446,12 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
> case 0:
> regptr = &its->baser_device_table;
> entry_size = abi->dte_esz;
> - device_type = GITS_BASER_TYPE_DEVICE;
> + type = GITS_BASER_TYPE_DEVICE;
> break;
> case 1:
> regptr = &its->baser_coll_table;
> entry_size = abi->cte_esz;
> - device_type = GITS_BASER_TYPE_COLLECTION;
> + type = GITS_BASER_TYPE_COLLECTION;
> clearbits = GITS_BASER_INDIRECT;
> break;
> default:
> @@ -1462,10 +1463,28 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
> reg &= ~clearbits;
>
> reg |= (entry_size - 1) << GITS_BASER_ENTRY_SIZE_SHIFT;
> - reg |= device_type << GITS_BASER_TYPE_SHIFT;
> + reg |= (u64)type << GITS_BASER_TYPE_SHIFT;

Nit: Why having changed the type to being an int? The existing type (u64) was
perfectly sane, and avoids the ugly cast. Also, table_type would be more
explicit than the pretty generic "type".

> reg = vgic_sanitise_its_baser(reg);
>
> *regptr = reg;
> +
> + /*
> + * If the table is no longer valid, we clear the associated cached data.
> + * Note: there cannot be any race with save/restore code which locks
> + * all vcpus.
> + */
> + if (!(reg & GITS_BASER_VALID)) {
> + switch (type) {
> + case GITS_BASER_TYPE_DEVICE:
> + vgic_its_free_device_list(kvm, its);
> + break;
> + case GITS_BASER_TYPE_COLLECTION:
> + vgic_its_free_collection_list(kvm, its);
> + break;
> + default:
> + break;

Nit: this default clause is useless.

> + }
> + }
> }
>
> static unsigned long vgic_mmio_read_its_ctlr(struct kvm *vcpu,

Otherwise:

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

M.
--
Jazz is not dead. It just smells funny.