[PATCH v5 16/22] KVM: arm64: vgic-its: Add infrastructure for table lookup

[Auger Eric]

Hi Christoffer,

On 30/04/2017 21:35, Christoffer Dall wrote:
> On Fri, Apr 14, 2017 at 12:15:28PM +0200, Eric Auger wrote:
>> Add a generic lookup_table() helper whose role consists in
>> scanning a contiguous table located in guest RAM and applying
>> a callback on each entry. Entries can be handled as linked lists
>> since the callback may return an offset to the next entry and
>> also tell that an entry is the last one.
>>
>> Helper functions also are added to compute the device/event ID
>> offset to the next DTE/ITE.
>>
>> compute_next_devid_offset, compute_next_eventid_offset and
>> lookup_table will become static in subsequent patches
>>
>> Signed-off-by: Eric Auger <eric.auger at redhat.com>
>>
>> ---
>> v4 -> v5:
>> - use kvm_read_guest
>>
>> v3 -> v4:
>> - remove static to avoid compilation warning
>> - correct size computation in looup_table()
>> - defines now encode the number of bits used for devid and eventid offsets
>> - use BIT() - 1 to encode the max offets
>> ---
>>  virt/kvm/arm/vgic/vgic-its.c | 93 ++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 93 insertions(+)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>> index 56c5123..c22b35d 100644
>> --- a/virt/kvm/arm/vgic/vgic-its.c
>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>> @@ -195,6 +195,8 @@ static struct its_ite *find_ite(struct vgic_its *its, u32 device_id,
>>  
>>  #define VITS_TYPER_IDBITS 16
>>  #define VITS_TYPER_DEVBITS 16
>> +#define VITS_DTE_MAX_DEVID_OFFSET	(BIT(14) - 1)
>> +#define VITS_ITE_MAX_EVENTID_OFFSET	(BIT(16) - 1)
>>  
>>  /*
>>   * Finds and returns a collection in the ITS collection table.
>> @@ -1674,6 +1676,97 @@ int vgic_its_attr_regs_access(struct kvm_device *dev,
>>  	return ret;
>>  }
>>  
>> +u32 compute_next_devid_offset(struct list_head *h, struct its_device *dev)
>> +{
>> +	struct list_head *e = &dev->dev_list;
>> +	struct its_device *next;
>> +	u32 next_offset;
>> +
>> +	if (e->next == h)
>> +		return 0;
>> +	next = list_entry(e->next, struct its_device, dev_list);
>> +	next_offset = next->device_id - dev->device_id;
>> +
>> +	return min_t(u32, next_offset, VITS_DTE_MAX_DEVID_OFFSET);
>> +}
>> +
>> +u32 compute_next_eventid_offset(struct list_head *h, struct its_ite *ite)
>> +{
>> +	struct list_head *e = &ite->ite_list;
>> +	struct its_ite *next;
>> +	u32 next_offset;
>> +
>> +	if (e->next == h)
>> +		return 0;
>> +	next = list_entry(e->next, struct its_ite, ite_list);
>> +	next_offset = next->event_id - ite->event_id;
>> +
>> +	return min_t(u32, next_offset, VITS_ITE_MAX_EVENTID_OFFSET);
>> +}
>> +
>> +/**
>> + * entry_fn_t - Callback called on a table entry restore path
>> + * @its: its handle
>> + * @id: id of the entry
>> + * @entry: pointer to the entry
>> + * @opaque: pointer to an opaque data
>> + * @next_offset: minimal ID offset to the next entry. 0 if this
>> + * entry is the last one, 1 if the entry is invalid, >= 1 if an
> 
> eh, also, did you mean -1 if the entry is invalid?
no in case the entry is invalid, we tell the caller that it must inspect
the next entry, hence the next_offset = +1.

Thanks

Eric
> 
> Thanks,
> -Christoffer
>