Re: [RFC v7 2/7] KVM: kvm_host: add devid in kvm_kernel_irq_routing_entry

[Marc Zyngier <marc.zyngier@arm.com>]

On 21/07/16 18:22, Radim Krčmář wrote:
> 2016-07-21 17:54+0100, Marc Zyngier:
>> On 21/07/16 17:13, Radim Krčmář wrote:
>>> 2016-07-18 13:25+0000, Eric Auger:
>>>> Extend kvm_kernel_irq_routing_entry to transport the device id
>>>> field, devid. A new flags field makes possible to indicate the
>>>> devid is valid. Those additions are used for ARM GICv3 ITS MSI
>>>> injection.
>>>>
>>>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>>> Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
>>>>
>>>> ---
>>>> v6 -> v7:
>>>> - added msi_ prefix to flags and dev_id fields
>>>>
>>>> v4 -> v5:
>>>> - add Christoffer's R-b
>>>>
>>>> v2 -> v3:
>>>> - add flags
>>>>
>>>> v1 -> v2:
>>>> - replace msi_msg field by a struct composed of msi_msg and devid
>>>>
>>>> RFC -> PATCH:
>>>> - reword the commit message after change in first patch (uapi)
>>>> ---
>>>>  include/linux/kvm_host.h | 6 +++++-
>>>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>>>> index c87fe6f..3d2cbb4 100644
>>>> --- a/include/linux/kvm_host.h
>>>> +++ b/include/linux/kvm_host.h
>>>> @@ -317,7 +317,11 @@ struct kvm_kernel_irq_routing_entry {
>>>>  			unsigned irqchip;
>>>>  			unsigned pin;
>>>>  		} irqchip;
>>>> -		struct msi_msg msi;
>>>> +		struct {
>>>> +			struct msi_msg msi;
>>>> +			u32 msi_flags;
>>>> +			u32 msi_devid;
>>>
>>> I'd much rather see them as msi.flags and msi.devid.
>>
>> That's not really possible, as msi_msg is the core data structure for
>> MSIs, and nobody really expects this tructure to change.
>>
>>> I didn't notice a code that passes struct msi_msg anywhere, so using an
>>> ad-hoc struct like irqchip or defining a new one would work fine.
>>
>> I guess we could have an arm-specific one:
>>
>> 		struct arm_msi {
>> 			struct msi_msg msg;
>> 			u32 flags;
>> 			u32 devid;
>> 		};
>>
>> and use that. Would that be OK with you?
> 
> The feature wants to be arch-neutral, so I would rather ignore struct
> msi_msg.  kvm_kernel_irq_routing_entry practically mirrors routing
> entries from KVM API and there we have:
> 
>   struct kvm_msi {
>   	__u32 address_lo;
>   	__u32 address_hi;
>   	__u32 data;
>   	__u32 flags;
>   	__u32 devid;
>   	__u8  pad[12];
>   };
> 
> I think that something like
> 
>   struct {
>   	u32 address_lo;
>   	u32 address_hi;
>   	u32 data;
>   	u32 flags;
>   	u32 devid;
>   } msi;
> 
> would get us consistency, minimal changes to existing code, no namespace
> hierarchy, and no "." vs "_" mistakes at a good price of some code
> duplication and concept separation.

Fair enough. Eric, can you give this a try?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...