On 03/07/2017 01:26 PM, Andrew Cooper wrote: > On 07/03/17 18:18, Boris Ostrovsky wrote: >>>> Don't we need to pass vaddr down to all routines so that they select >>>> appropriate tables? You seem to always be choosing the first one. >>> IIUC, we clear whole page table subtree covered by one pgd entry. >>> So, no, there's no need to pass vaddr down. Just pointer to page table >>> entry is enough. >>> >>> But I know virtually nothing about Xen. Please re-check my reasoning. >> Yes, we effectively remove the whole page table for vaddr so I guess >> it's OK. >> >>> I would also appreciate help with getting x86 Xen code work with 5-level >>> paging enabled. For now I make CONFIG_XEN dependent on !CONFIG_X86_5LEVEL. >> Hmmm... that's a problem since this requires changes in the hypervisor >> and even if/when these changes are made older version of hypervisor >> still will not be able to run those guests. >> >> This affects only PV guests and there is a series under review that >> provides clean code separation with CONFIG_XEN_PV but because, for >> example, dom0 (Xen control domain) is PV this will significantly limit >> availability of dom0-capable kernels (because I assume distros will want >> to have CONFIG_X86_5LEVEL). > Wasn't the plan to be able to automatically detect 4 vs 5 level support, > and cope either way, so distros didn't have to ship two different builds > of Linux? > > If so, all we need to do git things to compile sensibly, and have the PV > entry code in Linux configure the rest of the kernel appropriately. I am not aware of any plans but this would obviously be the preferred route. -boris
