On 06/06/2010 04:06 PM, Avi Kivity wrote:
When we call rmap_remove(), we (almost) always immediately follow it by
an __set_spte() to a nonpresent pte. Since we need to perform the two
operations atomically, to avoid losing the dirty and accessed bits, introduce
a helper drop_spte() and convert all call sites.
The operation is still nonatomic at this point.
@@ -1498,13 +1502,14 @@ static void kvm_mmu_page_unlink_children(struct kvm *kvm,
ent&= PT64_BASE_ADDR_MASK;
mmu_page_remove_parent_pte(page_header(ent),
&pt[i]);
+ pt[i] = shadow_trap_nonpresent_pte;
} else {
if (is_large_pte(ent))
--kvm->stat.lpages;
- rmap_remove(kvm,&pt[i]);
+ drop_spte(kvm,&pt[i],
+ shadow_trap_nonpresent_pte);
}
}
- pt[i] = shadow_trap_nonpresent_pte;
}
}
Autotest points out that this transformation (and an identical one in
zap_pte) does not preserve the semantics; if the outer if () fails, the
new code does not update pt[i].
With the original line after the if () retained, autotest is happier.
--
error compiling committee.c: too many arguments to function
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