Re: [Xen-devel] [PATCH 0/4] xen: map foreign pages for shared rings by updating the PTEs directly

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.09.11 at 17:53, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
> [Resend as requested by Konrad.]
> 
> This series of patches allows the vmalloc_sync_all() to be removed
> from alloc_vm_area() by getting the hypervisor to update the PTEs (in
> init_mm) directly rather than having the hypervisor look in the
> current page tables to find the PTEs.
> 
> Once the hypervisor has updated the PTEs, the normal mechanism of
> syncing the page tables after a fault works as expected.

Did you actually test that, and namely the case where alloc_vm_area()
would result in a new top level page directory entry to get populated?
I cannot see how this new entry would propagate into other mm-s, and
hence I cannot see how you can do away with calling vmalloc_sync_all()
just by changing how leaf page table entries get populated.

Jan

> This mechanism doesn't currently work on the ia64 port as that does
> not support the GNTMAP_contains_pte flag.
> 
> David
> 
> 
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