Re: [PATCH] mm/highmem: Align-down to page the address for kunmap_flush_on_unmap()

[Matthew Wilcox]

On Thu, Jan 26, 2023 at 12:38:58PM -0800, Andrew Morton wrote:
> On Thu, 26 Jan 2023 15:33:46 +0100 "Fabio M. De Francesco" <fmdefrancesco@xxxxxxxxx> wrote:
> 
> > If ARCH_HAS_FLUSH_ON_KUNMAP is defined (PA-RISC case), __kunmap_local()
> > calls kunmap_flush_on_unmap(). The latter currently flushes the wrong
> > address (as confirmed by Matthew Wilcox and Helge Deller). Al Viro
> > proposed to call kunmap_flush_on_unmap() on an aligned-down to page
> > address in order to fix this issue. Consensus has been reached on this
> > solution.
> 
> What are the user-visible runtime effects of this flaw?

The version of this patch I sent out includes this information,
as well as the missed alignment for kunmap_atomic().