On 19.02.2021 17:45, Jan Beulich wrote: > The address of this page is used by the CPU only to recognize when to > access the virtual APIC page instead. No accesses would ever go to this > page. It only needs to be present in the (CPU) page tables so that > address translation will produce its address as result for respective > accesses. > > By making this page global, we also eliminate the need to refcount it, > or to assign it to any domain in the first place. > > Signed-off-by: Jan Beulich <jbeul...@suse.com> > --- > v2: Avoid insertion when !has_vlapic(). Split off change to > p2m_get_iommu_flags(). > --- > Hooking p2m insertion onto arch_domain_creation_finished() isn't very > nice, but I couldn't find any better hook (nor a good place where to > introduce a new one). In particular there look to be no hvm_funcs hooks > being used on a domain-wide basis (except for init/destroy of course). > I did consider connecting this to the setting of HVM_PARAM_IDENT_PT, but > considered this no better, the more that the tool stack could be smarter > and avoid setting that param when not needed.
While this patch was triggered not just by Julien's observation of the early p2m insertion being a problem, but also many earlier times of running into this odd code, it is - especially at this stage - perhaps a possible option to split the change into just the movement of the set_mmio_p2m_entry() invocation and all the rest, in order to defer that rest until after 4.15. Jan
