>>> On 07.02.19 at 17:44, <wei.l...@citrix.com> wrote:
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -4752,13 +4752,13 @@ static l3_pgentry_t *virt_to_xen_l3e(unsigned long v)
>
> if ( !pl3e )
> return NULL;
> - clear_page(pl3e);
> if ( locking )
> spin_lock(&map_pgdir_lock);
> if ( !(l4e_get_flags(*pl4e) & _PAGE_PRESENT) )
> {
> l4_pgentry_t l4e = l4e_from_paddr(__pa(pl3e), __PAGE_HYPERVISOR);
>
> + clear_page(pl3e);
Is this really an optimization? You treat avoiding to clear the page
in a hopefully infrequent case of a race for holding the spin lock
for quite a bit longer.
Jan
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