Re: [PATCH v4 1/3] x86/vmemmap: Drop handling of 4K unaligned vmemmap range

Oscar Salvador
2021-03-08T18:21:26Z

On Thu, Mar 04, 2021 at 07:50:10AM -0800, Dave Hansen wrote:
> On 3/1/21 12:32 AM, Oscar Salvador wrote:
> > remove_pte_table() is prepared to handle the case where either the
> > start or the end of the range is not PAGE aligned.
> > This cannot actually happen:
> >
> > __populate_section_memmap enforces the range to be PMD aligned,
> > so as long as the size of the struct page remains multiple of 8,
> > the vmemmap range will be aligned to PAGE_SIZE.
> >
> > Drop the dead code and place a VM_BUG_ON in vmemmap_{populate,free}
> > to catch nasty cases.
>
> I was wondering why the VM_BUG_ON()s went in vmemmap_free() instead of
> closer to the code that you modified in remove_pte_table(). I assume
> this was because vmemmap_free() is the only (indirect) caller of
> remove_pte_table().

Yes, that was pretty much the reason.
It seemed reasonable to me to fence it off at the "gate", and not further
deep.

Does it make sense to you? May I keep your Ack?

Thanks Dave!

>
> Otherwise, this looks fine to me:
>
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
>

--
Oscar Salvador
SUSE L3