Re: [RFC 1/6] KVM: api: add kvm_irq_routing_extended_msi

[Eric Auger <eric.auger@linaro.org>]

Hi André,
On 06/22/2015 06:32 PM, Andre Przywara wrote:
> Hi Eric,
> 
> On 18/06/15 18:40, Eric Auger wrote:
>> On ARM, the MSI msg (address and data) comes along with
>> out-of-band device ID information. The device ID encodes the device
>> that composes the MSI msg. Let's create a new routing entry structure
>> that enables to encode that information on top of standard MSI
>> message
>>
>> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>> ---
>>  Documentation/virtual/kvm/api.txt | 9 +++++++++
>>  include/uapi/linux/kvm.h          | 9 +++++++++
>>  2 files changed, 18 insertions(+)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index d20fd94..bcec91e 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -1419,6 +1419,7 @@ struct kvm_irq_routing_entry {
>>  		struct kvm_irq_routing_irqchip irqchip;
>>  		struct kvm_irq_routing_msi msi;
>>  		struct kvm_irq_routing_s390_adapter adapter;
>> +		struct kvm_irq_routing_extended_msi ext_msi;
>>  		__u32 pad[8];
>>  	} u;
>>  };
>> @@ -1427,6 +1428,7 @@ struct kvm_irq_routing_entry {
>>  #define KVM_IRQ_ROUTING_IRQCHIP 1
>>  #define KVM_IRQ_ROUTING_MSI 2
>>  #define KVM_IRQ_ROUTING_S390_ADAPTER 3
>> +#define KVM_IRQ_ROUTING_EXTENDED_MSI 4
>>  
>>  No flags are specified so far, the corresponding field must be set to zero.
>>  
>> @@ -1442,6 +1444,13 @@ struct kvm_irq_routing_msi {
>>  	__u32 pad;
>>  };
>>  
>> +struct kvm_irq_routing_extended_msi {
>> +	__u32 address_lo;
>> +	__u32 address_hi;
>> +	__u32 data;
>> +	__u32 devid;
>> +};
>> +
> 
> I wonder if we could re-use the existing struct kvm_irq_routing_msi,
> which has an u32 pad field already. Since we use a different type
> number, this should not break. Admittedly not the nicest thing, but
> reduces interface bloat:
> 
> struct kvm_irq_routing_msi {
> 	__u32 address_lo;
> 	__u32 address_hi;
> 	__u32 data;
> 	union {
> 		__u32 pad;
> 		__u32 devid;
> 	};
> };
> 
> to maintain backward compatibility on the userland source level.
I also envisioned that solution. I eventually chose adding a new struct,
for sake of homogeneity since the fellow kvm struct does not have such a
padding field: struct kvm_kernel_irq_routing_entry (kvm_host.h).

But I don't have a strong preference so if it is a general preference I
will follow, of course.

Thanks

Eric


> 
> Cheers,
> Andre.
> 
>>  struct kvm_irq_routing_s390_adapter {
>>  	__u64 ind_addr;
>>  	__u64 summary_addr;
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 2a23705..e3f65a0 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -829,6 +829,13 @@ struct kvm_irq_routing_msi {
>>  	__u32 pad;
>>  };
>>  
>> +struct kvm_irq_routing_extended_msi {
>> +	__u32 address_lo;
>> +	__u32 address_hi;
>> +	__u32 data;
>> +	__u32 devid;
>> +};
>> +
>>  struct kvm_irq_routing_s390_adapter {
>>  	__u64 ind_addr;
>>  	__u64 summary_addr;
>> @@ -841,6 +848,7 @@ struct kvm_irq_routing_s390_adapter {
>>  #define KVM_IRQ_ROUTING_IRQCHIP 1
>>  #define KVM_IRQ_ROUTING_MSI 2
>>  #define KVM_IRQ_ROUTING_S390_ADAPTER 3
>> +#define KVM_IRQ_ROUTING_EXTENDED_MSI 4
>>  
>>  struct kvm_irq_routing_entry {
>>  	__u32 gsi;
>> @@ -851,6 +859,7 @@ struct kvm_irq_routing_entry {
>>  		struct kvm_irq_routing_irqchip irqchip;
>>  		struct kvm_irq_routing_msi msi;
>>  		struct kvm_irq_routing_s390_adapter adapter;
>> +		struct kvm_irq_routing_extended_msi ext_msi;
>>  		__u32 pad[8];
>>  	} u;
>>  };
>>

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