Re: [PATCH v5 3/4] x86/time: introduce command line option to select wallclock

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.09.2024 16:54, Roger Pau Monne wrote:
> Allow setting the used wallclock from the command line.  When the option is 
> set
> to a value different than `auto` the probing is bypassed and the selected
> implementation is used (as long as it's available).
> 
> The `xen` and `efi` options require being booted as a Xen guest (with Xen 
> guest
> supported built-in) or from UEFI firmware.

Perhaps add "respectively"?

> --- a/xen/arch/x86/time.c
> +++ b/xen/arch/x86/time.c
> @@ -1550,6 +1550,36 @@ static const char *__init 
> wallclock_type_to_string(void)
>      return "";
>  }
>  
> +static int __init cf_check parse_wallclock(const char *arg)
> +{
> +    if ( !arg )
> +        return -EINVAL;
> +
> +    if ( !strcmp("auto", arg) )
> +        wallclock_source = WALLCLOCK_UNSET;
> +    else if ( !strcmp("xen", arg) )
> +    {
> +        if ( !xen_guest )
> +            return -EINVAL;
> +
> +        wallclock_source = WALLCLOCK_XEN;
> +    }
> +    else if ( !strcmp("cmos", arg) )
> +        wallclock_source = WALLCLOCK_CMOS;
> +    else if ( !strcmp("efi", arg) )
> +    {
> +        if ( !efi_enabled(EFI_RS) )
> +            return -EINVAL;

I'm afraid there's a problem here, and I'm sorry for not paying attention
earlier: EFI_RS is possibly affected by "efi=" (and hence may change after
this code ran). (It can also be cleared if ->SetVirtualAddressMap() fails,
but I think that's strictly ahead of command line parsing.)

Jan