Re: [PATCH] x86/mm: Don't try to change poison pages to uncacheable in a guest

[Dan Williams]

On Mon, May 18, 2020 at 11:26 AM Luck, Tony <tony.luck@xxxxxxxxx> wrote:
[..]
> N.B. Linux wants to switch the page to uncacheable so that in the
> persistant memory case the filesytem code can continue to access
> the other "blocks" in the page, rather than lose all of them. That's
> futile in the case where the VMM took the whole 4K away. Maybe Dan
> needs to think about the guest case too.

I think increasing the blast-radius to 4K is the best we can do
without a paravirt mechanism to coordinate errors. There's also the
existing problem that set_mce_nospec() fails on pmem due to the
memtype lookup.