Marcelo Tosatti wrote:
What i'm saying is with shadow and NPT (i believe) you can mark a spte
writable but not dirty, which gives you the ability to know whether
certain pages have been dirtied.
Isnt this what this patch is doing?
Should be ok todo that with shadow, as long as the gpte is already
dirty, right? So:
- guest create writable pte
- guest write fault on that pte
- vmexit
- write dirty bit to gpte
- create writable spte
->
from this point on, you can create a writable spte which is not dirtied,
and use the dirty bit to know whether a page has been written to?
And unless i'm mistaken NPT gives you that for free since the hw updates
the spte with accessed/dirty bits.
Yes
Maybe this is a stupid idea.
I dont sure if i am missing it, or if this what i tried to do with this
patch.
* EPT violations do no transfer fault information to the page fault
handler, but its available (there's a vm-exit field).
EPT in this patch, run as before, (using page faults with
mark_page_dirty() inside set_spte())
Right, i was talking about gup(write=0) when guest fault is read-only to
relief KSM of wrprotecting host ptes, but that is quite different.
r = -ENOMEM;
@@ -1279,6 +1282,7 @@ int kvm_get_dirty_log(struct kvm *kvm,
if (!memslot->dirty_bitmap)
goto out;
+ kvm_arch_get_dirty_log(kvm, memslot);
n = ALIGN(memslot->npages, BITS_PER_LONG) / 8;
for (i = 0; !any && i < n/sizeof(long); ++i)
--
1.5.6.5
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Thanks :).
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