Re: [PATCH v13 22/24] virt: gunyah: Add irqfd interface

[Alex Elder]

On 5/9/23 3:47 PM, Elliot Berman wrote:
> Enable support for creating irqfds which can raise an interrupt on a
> Gunyah virtual machine. irqfds are exposed to userspace as a Gunyah VM
> function with the name "irqfd". If the VM devicetree is not configured
> to create a doorbell with the corresponding label, userspace will still
> be able to assert the eventfd but no interrupt will be raised on the
> guest.
>
> Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@xxxxxxxxxxx>
> Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@xxxxxxxxxxx>
> Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>

I have a minor suggestion.  I think I'd like to look at this
again, so:

Acked-by: Alex Elder <elder@xxxxxxxxxx>

> ---
>   Documentation/virt/gunyah/vm-manager.rst |   2 +-
>   drivers/virt/gunyah/Kconfig              |   9 ++
>   drivers/virt/gunyah/Makefile             |   1 +
>   drivers/virt/gunyah/gunyah_irqfd.c       | 180 +++++++++++++++++++++++
>   include/uapi/linux/gunyah.h              |  35 +++++
>   5 files changed, 226 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/virt/gunyah/gunyah_irqfd.c

. . .

> @@ -99,6 +102,38 @@ struct gh_fn_vcpu_arg {
>   	__u32 id;
>   };
>   
> +/**
> + * enum gh_irqfd_flags - flags for use in gh_fn_irqfd_arg
> + * @GH_IRQFD_FLAGS_LEVEL: make the interrupt operate like a level triggered
> + *                        interrupt on guest side. Triggering IRQFD before
> + *                        guest handles the interrupt causes interrupt to
> + *                        stay asserted.
> + */
> +enum gh_irqfd_flags {
> +	GH_IRQFD_FLAGS_LEVEL		= 1UL << 0,

	BIT(0),			/* ? */

> +};
> +
> +/**
> + * struct gh_fn_irqfd_arg - Arguments to create an irqfd function.
> + *
> + * Create this function with &GH_VM_ADD_FUNCTION using type &GH_FN_IRQFD.
> + *
> + * Allows setting an eventfd to directly trigger a guest interrupt.
> + * irqfd.fd specifies the file descriptor to use as the eventfd.
> + * irqfd.label corresponds to the doorbell label used in the guest VM's devicetree.
> + *
> + * @fd: an eventfd which when written to will raise a doorbell
> + * @label: Label of the doorbell created on the guest VM
> + * @flags: see &enum gh_irqfd_flags
> + * @padding: padding bytes
> + */
> +struct gh_fn_irqfd_arg {
> +	__u32 fd;
> +	__u32 label;
> +	__u32 flags;
> +	__u32 padding;
> +};
> +
>   /**
>    * struct gh_fn_desc - Arguments to create a VM function
>    * @type: Type of the function. See &enum gh_fn_type.