On 07.09.2020 19:09, Roger Pau Monne wrote: > This reverts commit 81fd0d3ca4b2cd309403c6e8da662c325dd35750. > > Original commit only takes into account the APIC access page being a > 'special' page, but when running a PVH dom0 there are other pages that > also fulfill the 'special' page check but shouldn't have it's cache > type set to WB. > > For example the ACPI regions are identity mapped into the guest but > are also Xen heap pages, and forcing those to WB cache type is wrong.
Why is this wrong? Xen heap pages are RAM ones. Quite the opposite, _not_ forcing them to WB is going to cause cachability conflicts, unless their direct mapping entries also got changed to UC (which I think we want to avoid if at all possible). The cachability we select here is the one to be used by the hardware, not the one perceived by a domain (be it Dom0 or a DomU). > I've discovered this while trying to boot a PVH dom0, which fail to > boot with this commit applied. And what exactly is the deeper reason of the failure? Jan
