Re: [Xen-devel] [PATCH v2] Rationalize max_grant_frames and max_maptrack_frames handling

[Jan Beulich <jbeulich@xxxxxxxx>]

On 27.11.2019 15:37, Paul Durrant wrote:
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -789,7 +789,7 @@ void __init start_xen(unsigned long boot_phys_offset,
>          .flags = XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap,
>          .max_evtchn_port = -1,
>          .max_grant_frames = gnttab_dom0_frames(),
> -        .max_maptrack_frames = opt_max_maptrack_frames,
> +        .max_maptrack_frames = -1,
>      };
>      int rc;
>  
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -697,8 +697,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
>      struct xen_domctl_createdomain dom0_cfg = {
>          .flags = IS_ENABLED(CONFIG_TBOOT) ? XEN_DOMCTL_CDF_s3_integrity : 0,
>          .max_evtchn_port = -1,
> -        .max_grant_frames = opt_max_grant_frames,
> -        .max_maptrack_frames = opt_max_maptrack_frames,
> +        .max_grant_frames = -1,
> +        .max_maptrack_frames = -1,
>      };

With these there's no need anymore for opt_max_maptrack_frames to
be non-static. Sadly Arm still wants opt_max_grant_frames
accessible in gnttab_dom0_frames().

> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -1837,12 +1837,18 @@ active_alloc_failed:
>      return -ENOMEM;
>  }
>  
> -int grant_table_init(struct domain *d, unsigned int max_grant_frames,
> -                     unsigned int max_maptrack_frames)
> +int grant_table_init(struct domain *d, int max_grant_frames,
> +                     int max_maptrack_frames)
>  {
>      struct grant_table *gt;
>      int ret = -ENOMEM;
>  
> +    /* Default to maximum value if no value was specified */
> +    if ( max_grant_frames < 0 )
> +        max_grant_frames = opt_max_grant_frames;
> +    if ( max_maptrack_frames < 0 )
> +        max_maptrack_frames = opt_max_maptrack_frames;
> +
>      if ( max_grant_frames < INITIAL_NR_GRANT_FRAMES ||

I take it we don't expect people to specify 2^^31 or more
frames for either option. It looks like almost everything
here would cope, except for this very comparison. Nevertheless
I wonder whether you wouldn't better confine both values to
[0, INT_MAX] now, including when adjusted at runtime.

Jan

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