Re: [PATCH v2 4/4] x86/vmalloc: Add TLB efficient x86 arch_vunmap

Nadav Amit
2018-12-12T06:31:03Z

> On Dec 11, 2018, at 4:03 PM, Rick Edgecombe <rick.p.edgecombe@intel.com> wrote:
>
> This adds a more efficient x86 architecture specific implementation of
> arch_vunmap, that can free any type of special permission memory with only 1 TLB
> flush.
>
> In order to enable this, _set_pages_p and _set_pages_np are made non-static and
> renamed set_pages_p_noflush and set_pages_np_noflush to better communicate
> their different (non-flushing) behavior from the rest of the set_pages_*
> functions.
>
> The method for doing this with only 1 TLB flush was suggested by Andy
> Lutomirski.
>

[snip]

> + /*
> + * If the vm being freed has security sensitive capabilities such as
> + * executable we need to make sure there is no W window on the directmap
> + * before removing the X in the TLB. So we set not present first so we
> + * can flush without any other CPU picking up the mapping. Then we reset
> + * RW+P without a flush, since NP prevented it from being cached by
> + * other cpus.
> + */
> + set_area_direct_np(area);
> + vm_unmap_aliases();

Does vm_unmap_aliases() flush in the TLB the direct mapping range as well? I
can only find the flush of the vmalloc range.