At some call sites of rmap_get_first() and rmap_get_next(), BUG_ON is
placed right after the call to detect unrelated sptes which must not be
found in the reverse-mapping list.
Move this check in rmap_get_first/next() so that all call sites, not
just the users of the for_each_rmap_spte() macro, will be checked the
same way. In addition, change the BUG_ON to WARN_ON since killing the
whole host is the last thing that KVM should try.
One thing to keep in mind is that kvm_mmu_unlink_parents() also uses
rmap_get_first() to handle parent sptes. The change will not break it
because parent sptes are present, at least until drop_parent_pte()
actually unlinks them, and not mmio-sptes.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@xxxxxxxxxxxxx>
---
Documentation/virtual/kvm/mmu.txt | 4 ++--
arch/x86/kvm/mmu.c | 26 +++++++++++++++++---------
2 files changed, 19 insertions(+), 11 deletions(-)
diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
index 3a4d681..daf9c0f 100644
--- a/Documentation/virtual/kvm/mmu.txt
+++ b/Documentation/virtual/kvm/mmu.txt
@@ -203,10 +203,10 @@ Shadow pages contain the following information:
page cannot be destroyed. See role.invalid.
parent_ptes:
The reverse mapping for the pte/ptes pointing at this page's spt. If
- parent_ptes bit 0 is zero, only one spte points at this pages and
+ parent_ptes bit 0 is zero, only one spte points at this page and
parent_ptes points at this single spte, otherwise, there exists multiple
sptes pointing at this page and (parent_ptes & ~0x1) points at a data
- structure with a list of parent_ptes.
+ structure with a list of parent sptes.
unsync:
If true, then the translations in this page may not match the guest's
translation. This is equivalent to the state of the tlb when a pte is
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 1691171..ee7b101 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1079,17 +1079,23 @@ struct rmap_iterator {
*/
static u64 *rmap_get_first(unsigned long rmap, struct rmap_iterator *iter)
{
+ u64 *sptep;
+
if (!rmap)
return NULL;
if (!(rmap & 1)) {
iter->desc = NULL;
- return (u64 *)rmap;
+ sptep = (u64 *)rmap;
+ goto out;
}
iter->desc = (struct pte_list_desc *)(rmap & ~1ul);
iter->pos = 0;
- return iter->desc->sptes[iter->pos];
+ sptep = iter->desc->sptes[iter->pos];
+out:
+ WARN_ON(!is_shadow_present_pte(*sptep));
+ return sptep;
}
/*
@@ -1099,14 +1105,14 @@ static u64 *rmap_get_first(unsigned long rmap, struct rmap_iterator *iter)
*/
static u64 *rmap_get_next(struct rmap_iterator *iter)
{
+ u64 *sptep;
+
if (iter->desc) {
if (iter->pos < PTE_LIST_EXT - 1) {
- u64 *sptep;
-
++iter->pos;
sptep = iter->desc->sptes[iter->pos];
if (sptep)
- return sptep;
+ goto out;
}
iter->desc = iter->desc->more;
@@ -1114,17 +1120,20 @@ static u64 *rmap_get_next(struct rmap_iterator *iter)
if (iter->desc) {
iter->pos = 0;
/* desc->sptes[0] cannot be NULL */
- return iter->desc->sptes[iter->pos];
+ sptep = iter->desc->sptes[iter->pos];
+ goto out;
}
}
return NULL;
+out:
+ WARN_ON(!is_shadow_present_pte(*sptep));
+ return sptep;
}
#define for_each_rmap_spte(_rmap_, _iter_, _spte_) \
for (_spte_ = rmap_get_first(*_rmap_, _iter_); \
- _spte_ && ({BUG_ON(!is_shadow_present_pte(*_spte_)); 1;}); \
- _spte_ = rmap_get_next(_iter_))
+ _spte_; _spte_ = rmap_get_next(_iter_))
static void drop_spte(struct kvm *kvm, u64 *sptep)
{
@@ -1338,7 +1347,6 @@ static bool kvm_zap_rmapp(struct kvm *kvm, unsigned long *rmapp)
bool flush = false;
while ((sptep = rmap_get_first(*rmapp, &iter))) {
- BUG_ON(!(*sptep & PT_PRESENT_MASK));
rmap_printk("%s: spte %p %llx.\n", __func__, sptep, *sptep);
drop_spte(kvm, sptep);
--
2.1.0
--
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