Linux Virtualization - May 2019 - [PATCH 08/10] virtio/s390: add indirection to indicators access

On 08/05/2019 16:31, Pierre Morel wrote:
> On 26/04/2019 20:32, Halil Pasic wrote:
>> This will come in handy soon when we pull out the indicators from
>> virtio_ccw_device to a memory area that is shared with the hypervisor
>> (in particular for protected virtualization guests).
>>
>> Signed-off-by: Halil Pasic <pasic at linux.ibm.com>
>> ---
>> ? drivers/s390/virtio/virtio_ccw.c | 40 
>> +++++++++++++++++++++++++---------------
>> ? 1 file changed, 25 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/s390/virtio/virtio_ccw.c 
>> b/drivers/s390/virtio/virtio_ccw.c
>> index bb7a92316fc8..1f3e7d56924f 100644
>> --- a/drivers/s390/virtio/virtio_ccw.c
>> +++ b/drivers/s390/virtio/virtio_ccw.c
>> @@ -68,6 +68,16 @@ struct virtio_ccw_device {
>> ????? void *airq_info;
>> ? };
>> +static inline unsigned long *indicators(struct virtio_ccw_device
*vcdev)
>> +{
>> +??? return &vcdev->indicators;
>> +}
>> +
>> +static inline unsigned long *indicators2(struct virtio_ccw_device 
>> *vcdev)
>> +{
>> +??? return &vcdev->indicators2;
>> +}
>> +
>> ? struct vq_info_block_legacy {
>> ????? __u64 queue;
>> ????? __u32 align;
>> @@ -337,17 +347,17 @@ static void virtio_ccw_drop_indicator(struct 
>> virtio_ccw_device *vcdev,
>> ????????? ccw->cda = (__u32)(unsigned long) thinint_area;
>> ????? } else {
>> ????????? /* payload is the address of the indicators */
>> -??????? indicatorp = kmalloc(sizeof(&vcdev->indicators),
>> +??????? indicatorp = kmalloc(sizeof(indicators(vcdev)),
>> ?????????????????????? GFP_DMA | GFP_KERNEL);
>> ????????? if (!indicatorp)
>> ????????????? return;
>> ????????? *indicatorp = 0;
>> ????????? ccw->cmd_code = CCW_CMD_SET_IND;
>> -??????? ccw->count = sizeof(&vcdev->indicators);
>> +??????? ccw->count = sizeof(indicators(vcdev));
> 
> This looks strange to me. Was already weird before.
> Lucky we are indicators are long...
> may be just sizeof(long)

AFAIK the size of the indicators (AIV/AIS) is not restricted by the 
architecture.
However we never use more than 64 bits, do we ever have an adapter 
having more than 64 different interrupts?

May be we can state than we use a maximal number of AISB of 64 and 
therefor use indicators with a size of unsigned long, or __u64 or 
whatever is appropriate. Please clear this.

With this cleared:
Reviewed-by: Pierre Morel<pmorel at linux.ibm.com>


Regards,
Pierre


-- 
Pierre Morel
Linux/KVM/QEMU in B?blingen - Germany

On 09/05/2019 20:26, Halil Pasic wrote:
> On Thu, 9 May 2019 14:01:01 +0200
> Pierre Morel <pmorel at linux.ibm.com> wrote:
> 
>> On 08/05/2019 16:31, Pierre Morel wrote:
>>> On 26/04/2019 20:32, Halil Pasic wrote:
>>>> This will come in handy soon when we pull out the indicators
from
>>>> virtio_ccw_device to a memory area that is shared with the
hypervisor
>>>> (in particular for protected virtualization guests).
>>>>
>>>> Signed-off-by: Halil Pasic <pasic at linux.ibm.com>
>>>> ---
>>>>  ? drivers/s390/virtio/virtio_ccw.c | 40
>>>> +++++++++++++++++++++++++---------------
>>>>  ? 1 file changed, 25 insertions(+), 15 deletions(-)
>>>>
>>>> diff --git a/drivers/s390/virtio/virtio_ccw.c
>>>> b/drivers/s390/virtio/virtio_ccw.c
>>>> index bb7a92316fc8..1f3e7d56924f 100644
>>>> --- a/drivers/s390/virtio/virtio_ccw.c
>>>> +++ b/drivers/s390/virtio/virtio_ccw.c
>>>> @@ -68,6 +68,16 @@ struct virtio_ccw_device {
>>>>  ????? void *airq_info;
>>>>  ? };
>>>> +static inline unsigned long *indicators(struct
virtio_ccw_device *vcdev)
>>>> +{
>>>> +??? return &vcdev->indicators;
>>>> +}
>>>> +
>>>> +static inline unsigned long *indicators2(struct
virtio_ccw_device
>>>> *vcdev)
>>>> +{
>>>> +??? return &vcdev->indicators2;
>>>> +}
>>>> +
>>>>  ? struct vq_info_block_legacy {
>>>>  ????? __u64 queue;
>>>>  ????? __u32 align;
>>>> @@ -337,17 +347,17 @@ static void
virtio_ccw_drop_indicator(struct
>>>> virtio_ccw_device *vcdev,
>>>>  ????????? ccw->cda = (__u32)(unsigned long) thinint_area;
>>>>  ????? } else {
>>>>  ????????? /* payload is the address of the indicators */
>>>> -??????? indicatorp =
kmalloc(sizeof(&vcdev->indicators),
>>>> +??????? indicatorp = kmalloc(sizeof(indicators(vcdev)),
>>>>  ?????????????????????? GFP_DMA | GFP_KERNEL);
>>>>  ????????? if (!indicatorp)
>>>>  ????????????? return;
>>>>  ????????? *indicatorp = 0;
>>>>  ????????? ccw->cmd_code = CCW_CMD_SET_IND;
>>>> -??????? ccw->count = sizeof(&vcdev->indicators);
>>>> +??????? ccw->count = sizeof(indicators(vcdev));
>>>
>>> This looks strange to me. Was already weird before.
>>> Lucky we are indicators are long...
>>> may be just sizeof(long)
>>
> 
> I'm not sure I understand where are you coming from...
> 
> With CCW_CMD_SET_IND we tell the hypervisor the guest physical address
> at which the so called classic indicators. There is a comment that
> makes this obvious. The argument of the sizeof was and remained a
> pointer type. AFAIU this is what bothers you.
>>
>> AFAIK the size of the indicators (AIV/AIS) is not restricted by the
>> architecture.
> 
> The size of vcdev->indicators is restricted or defined by the virtio
> specification. Please have a look at '4.3.2.6.1 Setting Up Classic
Queue
> Indicators' here:
>
https://docs.oasis-open.org/virtio/virtio/v1.1/cs01/virtio-v1.1-cs01.html#x1-1630002
> 
> Since with Linux on s390 only 64 bit is supported, both the sizes are in
> line with the specification. Using u64 would semantically match the spec
> better, modulo pre virtio 1.0 which ain't specified. I did not want to
> do changes that are not necessary for what I'm trying to accomplish. If
> we want we can change these to u64 with a patch on top.
I mean you are changing these line already, so why not doing it right 
while at it?

Pierre

-- 
Pierre Morel
Linux/KVM/QEMU in B?blingen - Germany