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

[Elliot Berman]

On 6/5/2023 12:50 PM, Alex Elder wrote:
> 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),            /* ? */

The BIT macro isn't a standard C macro and isn't defined by Linux, so it 
causes compile errors at least for me when I use it in userspace.

> > +};
> > +
> > +/**
> > + * 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.