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

Auger Eric
2017-04-11T09:57:46Z

Hi Marc,

On 10/04/2017 11:55, Marc Zyngier wrote:
> 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?
At the moment its_collection.target_addr is u32 and corresponds to the
PE number. Only GITS_TYPER.PTA = 0 is supported.

Or do I miss something?

Thanks

Eric
>
>> + 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.
>