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

[Marc Zyngier <marc.zyngier@arm.com>]

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...