Re: [PATCH v4 18/22] KVM: arm64: ITS: Collection table save/restore

Marc Zyngier
2017-04-10T09:55:40Z

On 27/03/17 10:31, Eric Auger wrote:
> The flush path copies the collection entries into guest RAM
> at the GPA specified in the BASER register. This obviously
> requires the BASER to be set. The last written element
> is a dummy collection table entry.
>
> We do not index by collection ID as the collection entry
> can fit into 8 bytes while containing the collection ID.
>
> On restore path we re-allocate the collection objects.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
>
> v3 -> v4:
> - replaced u64 *ptr by gpa_t gpa
> - check the collection does not exist before allocating it
>
> v1 -> v2:
> - reword commit message and directly use 8 as entry size
> - no kvm parameter anymore
> - add helper for flush/restore cte
> - table size computed here
> - add le64/cpu conversions
> ---
> virt/kvm/arm/vgic/vgic-its.c | 99 +++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 97 insertions(+), 2 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 8eaeba4..df984b6 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1828,13 +1828,89 @@ static int vgic_its_restore_device_tables(struct vgic_its *its)
> return -ENXIO;
> }
>
> +static int vgic_its_flush_cte(struct vgic_its *its,
> + struct its_collection *collection, gpa_t gpa)

Given that the pendent of this function is name ..._restore_..., should
this be called ..._save_... ?

> +{
> + u64 val;
> + int ret;
> +
> + val = ((u64)1 << 63 | ((u64)collection->target_addr << 16) |
> + collection->collection_id);

Please provide some #defines that describe the encoding. This will be
specially useful if we need to export this to userspace (KVM/TCG
interoperability?).

> + val = cpu_to_le64(val);
> + ret = kvm_write_guest(its->dev->kvm, gpa, &val, 8);
> + return ret;
> +}
> +
> +static int vgic_its_restore_cte(struct vgic_its *its, gpa_t gpa, bool *valid)
> +{
> + struct its_collection *collection;
> + u32 target_addr;
> + u32 coll_id;
> + u64 val;
> + int ret;
> +
> + *valid = false;
> +
> + ret = kvm_read_guest(its->dev->kvm, gpa, &val, 8);
> + if (ret)
> + return ret;
> + val = le64_to_cpu(val);
> + *valid = val & BIT_ULL(63);
> +
> + if (!*valid)
> + return 0;
> +
> + target_addr = (u32)(val >> 16);

u32?

> + coll_id = val & 0xFFFF;

Same comment about the various shifts/masks.

> +
> + collection = find_collection(its, coll_id);
> + if (collection)
> + return -EEXIST;
> + ret = vgic_its_alloc_collection(its, &collection, coll_id);
> + if (ret)
> + return ret;
> + collection->target_addr = target_addr;
> + return 0;
> +}
> +
> /**
> * vgic_its_flush_collection_table - flush the collection table into
> * guest RAM
> */
> static int vgic_its_flush_collection_table(struct vgic_its *its)
> {
> - return -ENXIO;
> + struct its_collection *collection;
> + u64 val;
> + gpa_t gpa;
> + size_t max_size, filled = 0;
> + int ret;
> +
> + gpa = BASER_ADDRESS(its->baser_coll_table);
> + if (!gpa)
> + return 0;
> +
> + max_size = GITS_BASER_NR_PAGES(its->baser_coll_table) * SZ_64K;
> +
> + list_for_each_entry(collection, &its->collection_list, coll_list) {
> + if (filled == max_size)
> + return -ENOSPC;
> + ret = vgic_its_flush_cte(its, collection, gpa);
> + if (ret)
> + return ret;
> + gpa += 8;
> + filled += 8;

This "8" should be extracted from the BASER register itself (Entry_Size).

> + }
> +
> + if (filled == max_size)
> + return 0;
> +
> + /*
> + * table is not fully filled, add a last dummy element
> + * with valid bit unset
> + */
> + val = 0;
> + ret = kvm_write_guest(its->dev->kvm, gpa, &val, 8);
> + return ret;
> }
>
> /**
> @@ -1844,7 +1920,26 @@ static int vgic_its_flush_collection_table(struct vgic_its *its)
> */
> static int vgic_its_restore_collection_table(struct vgic_its *its)
> {
> - return -ENXIO;
> + size_t max_size, read = 0;
> + gpa_t gpa;
> + int ret;
> +
> + gpa = BASER_ADDRESS(its->baser_coll_table);
> + if (!gpa)
> + return 0;
> +
> + max_size = GITS_BASER_NR_PAGES(its->baser_coll_table) * SZ_64K;
> +
> + while (read < max_size) {
> + bool valid;
> +
> + ret = vgic_its_restore_cte(its, gpa, &valid);
> + if (!valid || ret)
> + break;
> + gpa += 8;
> + read += 8;
> + }
> + return ret;
> }
>
> /**
>

Thanks,

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