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

[Christoffer Dall <christoffer.dall@linaro.org>]

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/

> +- 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?

> +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
>