Re: [Xen-devel] [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code

[Ingo Molnar <mingo@xxxxxxxxxx>]

* David Vrabel <david.vrabel@xxxxxxxxxx> 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.

Thanks,

        Ingo

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