Re: [RFC v6 1/6] KVM: api: pass the devid in the msi routing entry

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Hi Eric,

On 06/07/16 09:47, 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@xxxxxxxxxx>

Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>

Cheers,
Andre.

> 
> ---
> v4 -> v5:
> - some rephrasing in api.txt according to Christoffer's comments
> 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 | 19 +++++++++++++++++--
>  include/uapi/linux/kvm.h          |  5 ++++-
>  2 files changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index f60b137..0065c8e 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -1468,7 +1468,11 @@ 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, specifies that the devid field contains
> +  a valid value.
> +- zero otherwise
>  
>  struct kvm_irq_routing_irqchip {
>  	__u32 irqchip;
> @@ -1479,9 +1483,20 @@ 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 requirement to
> +provide 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 d8c4c32..eb22208 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -879,7 +879,10 @@ 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 {
> 
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