Re: [PATCH] x86/mm: do not mark IO regions as Xen heap

[Jan Beulich <jbeulich@xxxxxxxx>]

On 10.09.2020 15:35, Roger Pau Monne wrote:
> arch_init_memory will treat all the gaps on the physical memory map
> between RAM regions as MMIO and use share_xen_page_with_guest in order
> to assign them to dom_io. This has the side effect of setting the Xen
> heap flag on such pages, and thus is_special_page would then return
> true which is an issue in epte_get_entry_emt because such pages will
> be forced to use write-back cache attributes.
> 
> Fix this by introducing a new helper to assign the MMIO regions to
> dom_io without setting the Xen heap flag on the pages, so that
> is_special_page will return false and the pages won't be forced to use
> write-back cache attributes.
> 
> Fixes: 81fd0d3ca4b2cd ('x86/hvm: simplify 'mmio_direct' check in 
> epte_get_entry_emt()')

Is this really the correct commit? I had this queued for backport,
and ended up discarding it from the queue based on this tag, just
to then noticing that I remembered correctly that I did backport
ca24b2ffdbd9 ("x86/hvm: set 'ipat' in EPT for special pages") to
the stable trees already. Isn't it _this_ commit which the change
here fixes?

Jan