Introduce a common API for walking the shadow page tables locklessly
that abstracts away whether the TDP MMU is enabled or not. This will be
used in a follow-up patch to support the TDP MMU in fast_page_fault.
The API can be used as follows:
struct shadow_page_walk walk;
walk_shadow_page_lockless_begin(vcpu);
if (!walk_shadow_page_lockless(vcpu, addr, &walk))
goto out;
... use `walk` ...
out:
walk_shadow_page_lockless_end(vcpu);
Note: Separating walk_shadow_page_lockless_begin() from
walk_shadow_page_lockless() seems superfluous at first glance but is
needed to support fast_page_fault() since it performs multiple walks
under the same begin/end block.
No functional change intended.
Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 96 ++++++++++++++++++++-------------
arch/x86/kvm/mmu/mmu_internal.h | 15 ++++++
arch/x86/kvm/mmu/tdp_mmu.c | 34 ++++++------
arch/x86/kvm/mmu/tdp_mmu.h | 6 ++-
4 files changed, 96 insertions(+), 55 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 1d0fe1445e04..8140c262f4d3 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -623,6 +623,11 @@ static bool mmu_spte_age(u64 *sptep)
static void walk_shadow_page_lockless_begin(struct kvm_vcpu *vcpu)
{
+ if (is_vcpu_using_tdp_mmu(vcpu)) {
+ kvm_tdp_mmu_walk_lockless_begin();
+ return;
+ }
+
/*
* Prevent page table teardown by making any free-er wait during
* kvm_flush_remote_tlbs() IPI to all active vcpus.
@@ -638,6 +643,11 @@ static void walk_shadow_page_lockless_begin(struct kvm_vcpu *vcpu)
static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu)
{
+ if (is_vcpu_using_tdp_mmu(vcpu)) {
+ kvm_tdp_mmu_walk_lockless_end();
+ return;
+ }
+
/*
* Make sure the write to vcpu->mode is not reordered in front of
* reads to sptes. If it does, kvm_mmu_commit_zap_page() can see us
@@ -3501,59 +3511,61 @@ static bool mmio_info_in_cache(struct kvm_vcpu *vcpu, u64 addr, bool direct)
}
/*
- * Return the level of the lowest level SPTE added to sptes.
- * That SPTE may be non-present.
+ * Walks the shadow page table for the given address until a leaf or non-present
+ * spte is encountered.
+ *
+ * Returns false if no walk could be performed, in which case `walk` does not
+ * contain any valid data.
+ *
+ * Must be called between walk_shadow_page_lockless_{begin,end}.
*/
-static int get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, int *root_level)
+static bool walk_shadow_page_lockless(struct kvm_vcpu *vcpu, u64 addr,
+ struct shadow_page_walk *walk)
{
- struct kvm_shadow_walk_iterator iterator;
- int leaf = -1;
+ struct kvm_shadow_walk_iterator it;
+ bool walk_ok = false;
u64 spte;
- walk_shadow_page_lockless_begin(vcpu);
+ if (is_vcpu_using_tdp_mmu(vcpu))
+ return kvm_tdp_mmu_walk_lockless(vcpu, addr, walk);
- for (shadow_walk_init(&iterator, vcpu, addr),
- *root_level = iterator.level;
- shadow_walk_okay(&iterator);
- __shadow_walk_next(&iterator, spte)) {
- leaf = iterator.level;
- spte = mmu_spte_get_lockless(iterator.sptep);
+ shadow_walk_init(&it, vcpu, addr);
+ walk->root_level = it.level;
- sptes[leaf] = spte;
+ for (; shadow_walk_okay(&it); __shadow_walk_next(&it, spte)) {
+ walk_ok = true;
+
+ spte = mmu_spte_get_lockless(it.sptep);
+ walk->last_level = it.level;
+ walk->sptes[it.level] = spte;
if (!is_shadow_present_pte(spte))
break;
}
- walk_shadow_page_lockless_end(vcpu);
-
- return leaf;
+ return walk_ok;
}
/* return true if reserved bit(s) are detected on a valid, non-MMIO SPTE. */
static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
{
- u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
+ struct shadow_page_walk walk;
struct rsvd_bits_validate *rsvd_check;
- int root, leaf, level;
+ int last_level, level;
bool reserved = false;
- if (!VALID_PAGE(vcpu->arch.mmu->root_hpa)) {
- *sptep = 0ull;
+ *sptep = 0ull;
+
+ if (!VALID_PAGE(vcpu->arch.mmu->root_hpa))
return reserved;
- }
- if (is_vcpu_using_tdp_mmu(vcpu))
- leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, &root);
- else
- leaf = get_walk(vcpu, addr, sptes, &root);
+ walk_shadow_page_lockless_begin(vcpu);
- if (unlikely(leaf < 0)) {
- *sptep = 0ull;
- return reserved;
- }
+ if (!walk_shadow_page_lockless(vcpu, addr, &walk))
+ goto out;
- *sptep = sptes[leaf];
+ last_level = walk.last_level;
+ *sptep = walk.sptes[last_level];
/*
* Skip reserved bits checks on the terminal leaf if it's not a valid
@@ -3561,29 +3573,37 @@ static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
* design, always have reserved bits set. The purpose of the checks is
* to detect reserved bits on non-MMIO SPTEs. i.e. buggy SPTEs.
*/
- if (!is_shadow_present_pte(sptes[leaf]))
- leaf++;
+ if (!is_shadow_present_pte(walk.sptes[last_level]))
+ last_level++;
rsvd_check = &vcpu->arch.mmu->shadow_zero_check;
- for (level = root; level >= leaf; level--)
+ for (level = walk.root_level; level >= last_level; level--) {
+ u64 spte = walk.sptes[level];
+
/*
* Use a bitwise-OR instead of a logical-OR to aggregate the
* reserved bit and EPT's invalid memtype/XWR checks to avoid
* adding a Jcc in the loop.
*/
- reserved |= __is_bad_mt_xwr(rsvd_check, sptes[level]) |
- __is_rsvd_bits_set(rsvd_check, sptes[level], level);
+ reserved |= __is_bad_mt_xwr(rsvd_check, spte) |
+ __is_rsvd_bits_set(rsvd_check, spte, level);
+ }
if (reserved) {
pr_err("%s: reserved bits set on MMU-present spte, addr 0x%llx, hierarchy:\n",
__func__, addr);
- for (level = root; level >= leaf; level--)
+ for (level = walk.root_level; level >= last_level; level--) {
+ u64 spte = walk.sptes[level];
+
pr_err("------ spte = 0x%llx level = %d, rsvd bits = 0x%llx",
- sptes[level], level,
- rsvd_check->rsvd_bits_mask[(sptes[level] >> 7) & 1][level-1]);
+ spte, level,
+ rsvd_check->rsvd_bits_mask[(spte >> 7) & 1][level-1]);
+ }
}
+out:
+ walk_shadow_page_lockless_end(vcpu);
return reserved;
}
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index d64ccb417c60..26da6ca30fbf 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -165,4 +165,19 @@ void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp);
void unaccount_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp);
+struct shadow_page_walk {
+ /* The level of the root spte in the walk. */
+ int root_level;
+
+ /*
+ * The level of the last spte in the walk. The last spte is either the
+ * leaf of the walk (which may or may not be present) or the first
+ * non-present spte encountered during the walk.
+ */
+ int last_level;
+
+ /* The spte value at each level. */
+ u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
+};
+
#endif /* __KVM_X86_MMU_INTERNAL_H */
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index f4cc79dabeae..36f4844a5f95 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1504,28 +1504,32 @@ bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm,
return spte_set;
}
-/*
- * Return the level of the lowest level SPTE added to sptes.
- * That SPTE may be non-present.
- */
-int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
- int *root_level)
+void kvm_tdp_mmu_walk_lockless_begin(void)
+{
+ rcu_read_lock();
+}
+
+void kvm_tdp_mmu_walk_lockless_end(void)
+{
+ rcu_read_unlock();
+}
+
+bool kvm_tdp_mmu_walk_lockless(struct kvm_vcpu *vcpu, u64 addr,
+ struct shadow_page_walk *walk)
{
struct tdp_iter iter;
struct kvm_mmu *mmu = vcpu->arch.mmu;
gfn_t gfn = addr >> PAGE_SHIFT;
- int leaf = -1;
+ bool walk_ok = false;
- *root_level = vcpu->arch.mmu->shadow_root_level;
-
- rcu_read_lock();
+ walk->root_level = vcpu->arch.mmu->shadow_root_level;
tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
- leaf = iter.level;
- sptes[leaf] = iter.old_spte;
- }
+ walk_ok = true;
- rcu_read_unlock();
+ walk->last_level = iter.level;
+ walk->sptes[iter.level] = iter.old_spte;
+ }
- return leaf;
+ return walk_ok;
}
diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index c8cf12809fcf..772d11bbb92a 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -76,8 +76,10 @@ bool kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm,
struct kvm_memory_slot *slot, gfn_t gfn);
-int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
- int *root_level);
+void kvm_tdp_mmu_walk_lockless_begin(void);
+void kvm_tdp_mmu_walk_lockless_end(void);
+bool kvm_tdp_mmu_walk_lockless(struct kvm_vcpu *vcpu, u64 addr,
+ struct shadow_page_walk *walk);
#ifdef CONFIG_X86_64
void kvm_mmu_init_tdp_mmu(struct kvm *kvm);
--
2.32.0.272.g935e593368-goog
