Subject: [PATCH 02/13] KVM: extend struct kvm_msi to hold a 32-bit device ID

From: [email-masked] (Christoffer Dall)
Date: Sun, 28 Jun 2015 21:12:34 +0200

On Fri, May 29, 2015 at 10:53:18AM +0100, Andre Przywara wrote:
> The ARM GICv3 ITS MSI controller requires a device ID to be able to
> assign the proper interrupt vector. On real hardware, this ID is
> sampled from the bus. To be able to emulate an ITS controller, extend
> the KVM MSI interface to let userspace provide such a device ID. For
> PCI devices, the device ID is simply the 16-bit bus-device-function
> triplet, which should be easily available to the userland tool.
> 
> Signed-off-by: Andre Przywara <[email-masked]>
> ---
>  Documentation/virtual/kvm/api.txt | 8 ++++++--
>  include/uapi/linux/kvm.h          | 4 +++-
>  2 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 9fa2bf8..891d64a 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2121,10 +2121,14 @@ struct kvm_msi {
>  	__u32 address_hi;
>  	__u32 data;
>  	__u32 flags;
> -	__u8  pad[16];
> +	__u32 devid;
> +	__u8  pad[12];
>  };
>  
> -No flags are defined so far. The corresponding field must be 0.
> +flags: KVM_MSI_VALID_DEVID: devid is valid, otherwise ignored.

I don't see what the 'otherwise ignored' part of the sentence here is
meant to say, that the flags field is otherwise ignored for other value?
That's not what the current API doc specifies, it specifies that the
remainder of the field must be 0.

> +devid: If KVM_MSI_VALID_DEVID is set, contains a value to identify the device
> +       that wrote the MSI message. For PCI, this is usually a BFD
> +       identifier in the lower 16 bits.

I assume plus something else that uniquely identifies the PCI
controller?

-Christoffer

>  
>  
>  4.71 KVM_CREATE_PIT2
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 4b60056..2a23705 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -965,12 +965,14 @@ struct kvm_one_reg {
>  	__u64 addr;
>  };
>  
> +#define KVM_MSI_VALID_DEVID	(1U << 0)
>  struct kvm_msi {
>  	__u32 address_lo;
>  	__u32 address_hi;
>  	__u32 data;
>  	__u32 flags;
> -	__u8  pad[16];
> +	__u32 devid;
> +	__u8  pad[12];
>  };
>  
>  struct kvm_arm_device_addr {
> -- 
> 2.3.5
>