Re: [PATCH v4 1/7] KVM: api: pass the devid in the msi routing entry

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

Christoffer,
On 04/14/2016 02:04 PM, Christoffer Dall wrote:
> On Mon, Apr 04, 2016 at 10:47:31AM +0200, 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 writes the MSI msg. Let's convey the device id in
>> kvm_irq_routing_msi and use KVM_MSI_VALID_DEVID flag value in
>> kvm_irq_routing_entry to indicate the msi devid is populated.
>>
>> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>>
>> ---
>> v2 -> v3:
>> - replace usage of KVM_IRQ_ROUTING_EXTENDED_MSI type by
>>   usage of KVM_MSI_VALID_DEVID flag
>> - add note about KVM_CAP_MSI_DEVID capability
>>
>> v1 -> v2:
>> - devid id passed in kvm_irq_routing_msi instead of in
>>   kvm_irq_routing_entry
>>
>> RFC -> PATCH
>> - remove kvm_irq_routing_extended_msi and use union instead
>> ---
>>  Documentation/virtual/kvm/api.txt | 18 ++++++++++++++++--
>>  include/uapi/linux/kvm.h          |  5 ++++-
>>  2 files changed, 20 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index 536f19b..c436bb6 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -1462,7 +1462,10 @@ struct kvm_irq_routing_entry {
>>  #define KVM_IRQ_ROUTING_S390_ADAPTER 3
>>  #define KVM_IRQ_ROUTING_HV_SINT 4
>>  
>> -No flags are specified so far, the corresponding field must be set to zero.
>> +flags:
>> +- KVM_MSI_VALID_DEVID: used along with KVM_IRQ_ROUTING_MSI
>> +  routing entry type, it tells the msi devid contains a valid value.
> 
> s/it tells the msi devid/specifies that the devid field/
ok
> 
>> +- zero otherwise
>>  
>>  struct kvm_irq_routing_irqchip {
>>  	__u32 irqchip;
>> @@ -1473,9 +1476,20 @@ struct kvm_irq_routing_msi {
>>  	__u32 address_lo;
>>  	__u32 address_hi;
>>  	__u32 data;
>> -	__u32 pad;
>> +	union {
>> +		__u32 pad;
>> +		__u32 devid;
>> +	};
>>  };
>>  
>> +devid: If KVM_MSI_VALID_DEVID is set, contains a unique device identifier
>> +       for the device that wrote the MSI message.
>> +       For PCI, this is usually a BFD identifier in the lower 16 bits.
>> +
>> +The per-VM KVM_CAP_MSI_DEVID capability advertises the need to provide
> 
> "the need to" or "the possibility to"?  Is there ever a situation where
> KVM_CAP_MSI_DEVID is set but you don't need to provide a device ID and
> set the flag?
I could replace by "requirement":
if it is not requested to pass a devid, we don't set the flag. If it is
we pass it.

if the user fails passing the devid and this ends up in the in-kernel
ITS emul, injection will fail.

Thanks

Eric
> 
>> +the device ID. If this capability is not set, userland cannot rely on
>> +the kernel to allow the KVM_MSI_VALID_DEVID flag being set.
>> +
>>  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 6a02871..52a973f 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -865,7 +865,10 @@ struct kvm_irq_routing_msi {
>>  	__u32 address_lo;
>>  	__u32 address_hi;
>>  	__u32 data;
>> -	__u32 pad;
>> +	union {
>> +		__u32 pad;
>> +		__u32 devid;
>> +	};
>>  };
>>  
>>  struct kvm_irq_routing_s390_adapter {
>> -- 
>> 1.9.1
>>