From mboxrd@z Thu Jan  1 00:00:00 1970
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [RFC v7 2/7] KVM: kvm_host: add devid in
 kvm_kernel_irq_routing_entry
Date: Thu, 21 Jul 2016 19:22:39 +0200
Message-ID: <20160721172239.GA9019@potion>
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Cc: Eric Auger <eric.auger@redhat.com>, eric.auger.pro@gmail.com,
	christoffer.dall@linaro.org, andre.przywara@arm.com,
	drjones@redhat.com, kvmarm@lists.cs.columbia.edu,
	kvm@vger.kernel.org, pbonzini@redhat.com
To: Marc Zyngier <marc.zyngier@arm.com>
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2016-07-21 17:54+0100, Marc Zyngier:
> On 21/07/16 17:13, Radim Kr=C4=8Dm=C3=A1=C5=99 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;
>>=20
>> I'd much rather see them as msi.flags and msi.devid.
>=20
> That's not really possible, as msi_msg is the core data structure for
> MSIs, and nobody really expects this tructure to change.
>=20
>> 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.
>=20
> I guess we could have an arm-specific one:
>=20
> 		struct arm_msi {
> 			struct msi_msg msg;
> 			u32 flags;
> 			u32 devid;
> 		};
>=20
> 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 namespac=
e
hierarchy, and no "." vs "_" mistakes at a good price of some code
duplication and concept separation.