Marcelo Tosatti wrote:
Under testing, count_writable_mappings returns a value that is 2 integers
larger than what count_rmaps returns.
Suspicion is that either of the two functions is counting a duplicate (either
positively or negatively).
Modifying check_writable_mappings_rmap to check for rmap existance on
all present MMU pages fails to trigger an error, which should keep Avi
happy.
Also introduce mmu_spte_walk to invoke a callback on all present sptes visible
to the current vcpu, might be useful in the future.
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Index: kvm/arch/x86/kvm/mmu.c
===================================================================
--- kvm.orig/arch/x86/kvm/mmu.c
+++ kvm/arch/x86/kvm/mmu.c
@@ -3017,6 +3017,55 @@ static gva_t canonicalize(gva_t gva)
return gva;
}
+
+typedef void (*inspect_spte_fn) (struct kvm *kvm, struct kvm_mmu_page *sp,
+ u64 *sptep);
+
+static void __mmu_spte_walk(struct kvm *kvm, struct kvm_mmu_page *sp,
+ inspect_spte_fn fn)
+{
+ int i;
+
+ for (i = 0; i < PT64_ENT_PER_PAGE; ++i) {
+ u64 ent = sp->spt[i];
+
+ if (is_shadow_present_pte(ent)) {
+ if (sp->role.level > 1) {
I think this is broken wrt large pages. We should recurse if role.level
> 1 or the G bit is set.
+ if (*sptep & PT_WRITABLE_MASK) {
+ rev_sp = page_header(__pa(sptep));
+ gfn = rev_sp->gfns[sptep - rev_sp->spt];
+
+ if (!gfn_to_memslot(kvm, gfn)) {
+ printk(KERN_ERR "%s: no memslot for gfn %ld\n",
+ audit_msg, gfn);
+ printk(KERN_ERR "%s: index %ld of sp (gfn=%lx)\n",
+ audit_msg, sptep - rev_sp->spt,
+ rev_sp->gfn);
+ dump_stack();
+ return;
+ }
+
+ rmapp = gfn_to_rmap(kvm, rev_sp->gfns[sptep - rev_sp->spt], 0);
+ if (!*rmapp) {
+ printk(KERN_ERR "%s: no rmap for writable spte %llx\n",
+ audit_msg, *sptep);
+ dump_stack();
+ }
+ }
Semi-related: we should set up a new exit code to halt the VM so it can
be inspected, otherwise all those printks and dump_stack()s will quickly
overwhelm the logging facilities.
--
error compiling committee.c: too many arguments to function
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