Hi Punit,
On 14/10/2016 13:25, Punit Agrawal wrote:
> Hi Eric,
>
> One query and a comment below.
>
> Eric Auger <eric.auger@xxxxxxxxxx> writes:
>
>> We introduce the capability to (un)register MSI doorbells.
>>
>> A doorbell region is characterized by its physical address base, size,
>> and whether it its safe (ie. it implements IRQ remapping). A doorbell
>> can be per-cpu or global. We currently only care about global doorbells.
>>
>> A function returns whether all registered doorbells are safe.
>>
>> MSI controllers likely to work along with IOMMU that translate MSI
>> transaction must register their doorbells to allow device assignment
>> with MSI support. Otherwise the MSI transactions will cause IOMMU faults.
>>
>> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>>
>> ---
>>
>> v13 -> v14:
>> - previously in msi-doorbell.h/c
>> ---
>> drivers/iommu/dma-iommu.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/dma-iommu.h | 41 ++++++++++++++++++++++++++
>> 2 files changed, 116 insertions(+)
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index d45f9a0..d8a7d86 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -43,6 +43,38 @@ struct iommu_dma_cookie {
>> spinlock_t msi_lock;
>> };
>>
>> +/**
>> + * struct iommu_msi_doorbell_info - MSI doorbell region descriptor
>> + * @percpu_doorbells: per cpu doorbell base address
>> + * @global_doorbell: base address of the doorbell
>> + * @doorbell_is_percpu: is the doorbell per cpu or global?
>> + * @safe: true if irq remapping is implemented
>> + * @size: size of the doorbell
>> + */
>> +struct iommu_msi_doorbell_info {
>> + union {
>> + phys_addr_t __percpu *percpu_doorbells;
>
> Out of curiosity, have you come across systems that have per-cpu
> doorbells? I couldn't find a system that'd help solidify my
> understanding on it's usage.
This came out after a discussion With Marc. However at the moment I am
not aware of any MSI controller featuring per-cpu doorbell. Not sure
whether it stays relevant to keep this notion at that stage.
>
>> + phys_addr_t global_doorbell;
>> + };
>> + bool doorbell_is_percpu;
>> + bool safe;
>
> Although you've got the comment above, 'safe' doesn't quite convey it's
> purpose. Can this be renamed to something more descriptive -
> 'intr_remapping' or 'intr_isolation' perhaps?
Yes definitively
Thanks
Eric
>
> Thanks,
> Punit
>
>
> [...]
>
>
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