Re: [Xen-devel] [PATCH RFC 13/55] x86/mm: rewrite virt_to_xen_l3e

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.02.19 at 17:44, <wei.liu2@xxxxxxxxxx> wrote:
> @@ -4769,45 +4769,70 @@ void free_xen_pagetable_new(mfn_t mfn)
>  
>  static DEFINE_SPINLOCK(map_pgdir_lock);
>  
> +/*
> + * Given a virtual address, return a pointer to xen's L3 entry. Caller
> + * needs to unmap the pointer.
> + */
>  static l3_pgentry_t *virt_to_xen_l3e(unsigned long v)
>  {
>      l4_pgentry_t *pl4e;
> +    l3_pgentry_t *pl3e = NULL;
>  
>      pl4e = &idle_pg_table[l4_table_offset(v)];
>      if ( !(l4e_get_flags(*pl4e) & _PAGE_PRESENT) )
>      {
>          bool locking = system_state > SYS_STATE_boot;
> -        l3_pgentry_t *l3t = alloc_xen_pagetable();
> +        l3_pgentry_t *l3t;
> +        mfn_t mfn;
> +
> +        mfn = alloc_xen_pagetable_new();
> +        if ( mfn_eq(mfn, INVALID_MFN) )
> +            goto out;

Any reason not to use "return NULL" here, avoiding the goto
and label altogether in tis function?

>  static l2_pgentry_t *virt_to_xen_l2e(unsigned long v)
>  {
>      l3_pgentry_t *pl3e;
> +    l2_pgentry_t *pl2e = NULL;
>  
>      pl3e = virt_to_xen_l3e(v);
>      if ( !pl3e )
> -        return NULL;
> +        goto out;

Why not keep this one the way it is?

Jan



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