Re: [Qemu-devel] [PATCH v2 15/16] postcopy: Check for userfault+hugepage feature

[Laurent Vivier]

On 06/02/2017 18:33, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> We need extra Linux kernel support (~4.11) to support userfaults
> on hugetlbfs; check for them.
> 
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> Reviewed-by: Juan Quintela <address@hidden>
> ---
>  migration/postcopy-ram.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 6b30b43..102fb61 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -81,6 +81,17 @@ static bool ufd_version_check(int ufd)
>          return false;
>      }
>  
> +    if (getpagesize() != ram_pagesize_summary()) {
> +        bool have_hp = false;
> +        /* We've got a huge page */
> +#ifdef UFFD_FEATURE_MISSING_HUGETLBFS
> +        have_hp = api_struct.features & UFFD_FEATURE_MISSING_HUGETLBFS;
> +#endif
> +        if (!have_hp) {
> +            error_report("Userfault on this host does not support huge 
> pages");
> +            return false;
> +        }
> +    }
>      return true;
>  }
>  
> @@ -115,7 +126,6 @@ bool postcopy_ram_supported_by_host(void)
>      if (!ufd_version_check(ufd)) {
>          goto out;
>      }
> -    /* TODO: Only allow huge pages if the kernel supports it */
>  
>      /*
>       * userfault and mlock don't go together; we'll put it back later if
> 
Reviewed-by: Laurent Vivier <address@hidden>