Messages in this thread | | | Date | Tue, 16 Jun 2015 15:15:48 +0100 | From | David Vrabel <> | Subject | Re: [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code |
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On 15/06/15 21:35, Ingo Molnar wrote: > > * David Vrabel <david.vrabel@citrix.com> wrote: > >> On 15/06/15 10:05, Ian Campbell wrote: >>> On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote: > >>>> xen_mm_pin_all()/unpin_all() are used to implement full guest instance >>>> suspend/restore. It's a stop-all method that needs to iterate through all >>>> allocated pgds in the system to fix them up for Xen's use. >>>> >>>> This code uses pgd_list, probably because it was an easy interface. >>>> >>>> But we want to remove the pgd_list, so convert the code over to walk all >>>> tasks in the system. This is an equivalent method. >> >> It is not equivalent because pgd_alloc() now populates entries in pgds that are >> not visible to xen_mm_pin_all() (note how the original code adds the pgd to the >> pgd_list in pgd_ctor() before calling pgd_prepopulate_pmd()). These newly >> allocated page tables won't be correctly converted on suspend/resume and the new >> process will die after resume. > > So how should the Xen logic be fixed for the new scheme? I can't say I can see > through the paravirt complexity here.
Actually, since we freeze_processes() before trying to pin page tables, I think it should be ok as-is.
I'll put the patch through some tests.
David
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