Re: [PATCH v2 08/10] KVM: arm/arm64: vgic-its: free caches when GITS_BASER Valid bit is cleared

Christoffer Dall
2017-10-13T15:19:37Z

On Wed, Sep 27, 2017 at 03:28:38PM +0200, Eric Auger wrote:
> When the GITS_BASER<n>.Valid gets cleared, the data structures in
> guest RAM are not provisionned anymore. The device, collection

provisioned

(but did you really mean valid?)

> 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>
> ---
> virt/kvm/arm/vgic/vgic-its.c | 23 +++++++++++++++++++----
> 1 file changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 0df6d5f..eaefba2 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1471,8 +1471,9 @@ 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)
> @@ -1482,12 +1483,12 @@ 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:
> @@ -1499,10 +1500,24 @@ 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;
> reg = vgic_sanitise_its_baser(reg);
>
> *regptr = reg;
> +
> + if (reg & GITS_BASER_VALID)
> + return;
> +
> + 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;
> + }

This block deserves a comment:
/* Table no longer valid: clear cached data */

I would also inverse the logic and do it within an if-statement if
(!(reg & GITS_BASER_VALID)), but it's up to you.

> }
>
> static unsigned long vgic_mmio_read_its_ctlr(struct kvm *vcpu,
> --
> 2.5.5
>

Thanks,
-Christoffer