Hi Pavel,
On 07/02/2015 09:26 AM, Pavel Fedin wrote:
> Hello!
>
>> -----Original Message-----
>> From: [email protected] [mailto:[email protected]] On Behalf
>> Of Eric Auger
>> Sent: Monday, June 29, 2015 6:37 PM
>> To: [email protected]; [email protected];
>> [email protected];
>> [email protected]; [email protected]; [email protected];
>> [email protected]; [email protected]
>> Cc: [email protected]; [email protected]; [email protected];
>> [email protected]
>> Subject: [PATCH 1/7] KVM: api: add kvm_irq_routing_extended_msi
>>
>> 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 type,
>> dubbed KVM_IRQ_ROUTING_EXTENDED_MSI and use the __u32 pad space
>> to convey the device ID.
>>
>> Signed-off-by: Eric Auger <[email protected]>
>>
>> ---
>>
>> RFC -> PATCH
>> - remove kvm_irq_routing_extended_msi and use union instead
>> ---
>> Documentation/virtual/kvm/api.txt | 9 ++++++++-
>> include/uapi/linux/kvm.h | 6 +++++-
>> 2 files changed, 13 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt
>> b/Documentation/virtual/kvm/api.txt
>> index d20fd94..6426ae9 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -1414,7 +1414,10 @@ struct kvm_irq_routing_entry {
>> __u32 gsi;
>> __u32 type;
>> __u32 flags;
>> - __u32 pad;
>> + union {
>> + __u32 pad;
>> + __u32 devid;
>> + };
>> union {
>> struct kvm_irq_routing_irqchip irqchip;
>> struct kvm_irq_routing_msi msi;
>
> devid is actually a part of MSI bunch. Shouldn't it be a part of struct
> kvm_irq_routing_msi then?
> It also has reserved pad.
Well this makes sense to me to associate the devid to the msi and put
devid in the pad field of struct kvm_irq_routing_msi.
André, Christoffer, would you agree on this change? - I would like to
avoid doing/undoing things ;-) -
>
>> @@ -1427,6 +1430,10 @@ 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
>> +
>> +In case of KVM_IRQ_ROUTING_EXTENDED_MSI routing type, devid is used to
>> convey
>> +the device ID.
>>
>> No flags are specified so far, the corresponding field must be set to zero.
>
> What if we use KVM_MSI_VALID_DEVID flag instead of new
> KVM_IRQ_ROUTING_EXTENDED_MSI definition? I
> believe this would make an API more consistent and introduce less new
> definitions.
do you mean using type == KVM_IRQ_ROUTING_MSI and flag ==
KVM_MSI_VALID_DEVID? Not sure this is simpler/clearer. s390 paved the
way for new routing entry types. I add a new one here.
Another solution may be to use new KVM_IRQ_ROUTING_EXTENDED_MSI type and
add struct kvm_msi ext_msi in kvm_irq_routing_entry union. It is 8 words
as well. But most probably this is even uglier.
Let's see if this thread is heading to a consensus...
Best Regards
Eric
>
>>
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 2a23705..8484681 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -841,12 +841,16 @@ 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;
>> __u32 type;
>> __u32 flags;
>> - __u32 pad;
>> + union {
>> + __u32 pad;
>> + __u32 devid;
>> + };
>> union {
>> struct kvm_irq_routing_irqchip irqchip;
>> struct kvm_irq_routing_msi msi;
>> --
>> 1.9.1
>>
>> --
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>
> Kind regards,
> Pavel Fedin
> Expert Engineer
> Samsung Electronics Research center Russia
>
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