Re: [PATCH v2 03/15] xen: harmonize return types of hypercall handlers

[Jan Beulich <jbeulich@xxxxxxxx>]

On 01.11.2021 16:20, Juergen Gross wrote:
> Today most hypercall handlers have a return type of long, while the
> compat ones return an int. There are a few exceptions from that rule,
> however.
> 
> Get rid of the exceptions by letting compat handlers always return int
> and others always return long.
> 
> For the compat hvm case use eax instead of rax for the stored result as
> it should have been from the beginning.
> 
> Additionally move some prototypes to include/asm-x86/hypercall.h
> as they are x86 specific. Move the do_physdev_op() prototype from both
> architecture dependant headers to the common one. Move the
> compat_platform_op() prototype to the common header.
> 
> Switch some non style compliant types (u32, s32, s64) to style compliant
> ones.
> 
> Rename paging_domctl_continuation() to do_paging_domctl_cont() and add
> a matching define for the associated hypercall.
> 
> Make do_callback_op() and compat_callback_op() more similar by adding
> the const attribute to compat_callback_op()'s 2nd parameter.
> 
> Change the type of the cmd parameter for [do|compat]_kexec_op() to
> unsigned int, as this is more appropriate for the compat case.

I continue to have reservations here, but I'll leave ack-ing of this
to the kexec maintainer.

> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one further nit:

> --- a/xen/arch/x86/x86_64/platform_hypercall.c
> +++ b/xen/arch/x86/x86_64/platform_hypercall.c
> @@ -4,10 +4,11 @@
>  
>  EMIT_FILE;
>  
> +#include <xen/hypercall.h>
> +#include <xen/types.h>
>  #include <xen/lib.h>
>  #include <compat/platform.h>

Would have been nice if the addition was done such that the result
was properly sorted; one way to do that would be to simply omit
xen/types.h which already gets included by xen/lib.h (and very
likely always will be).

Also I'm not convinced the do_get_debugreg() hoops are really
useful to retain if one way or another we need to rely on
implementation defined behavior anyway.

Jan