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Subject[PATCH 17/22] kvm: mmu: Support dirty logging for the TDP MMU
From
Dirty logging is a key feature of the KVM MMU and must be supported by
the TDP MMU. Add support for both the write protection and PML dirty
logging modes.

Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.

This series can be viewed in Gerrit at:
https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538

Signed-off-by: Ben Gardon <bgardon@google.com>
---
arch/x86/kvm/mmu/mmu.c | 19 +-
arch/x86/kvm/mmu/mmu_internal.h | 2 +
arch/x86/kvm/mmu/tdp_iter.c | 18 ++
arch/x86/kvm/mmu/tdp_iter.h | 1 +
arch/x86/kvm/mmu/tdp_mmu.c | 295 ++++++++++++++++++++++++++++++++
arch/x86/kvm/mmu/tdp_mmu.h | 10 ++
6 files changed, 343 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 0d80abe82ca93..b9074603f9df1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -201,7 +201,7 @@ static u64 __read_mostly shadow_nx_mask;
static u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
u64 __read_mostly shadow_user_mask;
u64 __read_mostly shadow_accessed_mask;
-static u64 __read_mostly shadow_dirty_mask;
+u64 __read_mostly shadow_dirty_mask;
static u64 __read_mostly shadow_mmio_value;
static u64 __read_mostly shadow_mmio_access_mask;
u64 __read_mostly shadow_present_mask;
@@ -324,7 +324,7 @@ inline bool spte_ad_enabled(u64 spte)
return (spte & SPTE_SPECIAL_MASK) != SPTE_AD_DISABLED_MASK;
}

-static inline bool spte_ad_need_write_protect(u64 spte)
+inline bool spte_ad_need_write_protect(u64 spte)
{
MMU_WARN_ON(is_mmio_spte(spte));
return (spte & SPTE_SPECIAL_MASK) != SPTE_AD_ENABLED_MASK;
@@ -1591,6 +1591,9 @@ static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
{
struct kvm_rmap_head *rmap_head;

+ if (kvm->arch.tdp_mmu_enabled)
+ kvm_tdp_mmu_clear_dirty_pt_masked(kvm, slot,
+ slot->base_gfn + gfn_offset, mask, true);
while (mask) {
rmap_head = __gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
PG_LEVEL_4K, slot);
@@ -1617,6 +1620,9 @@ void kvm_mmu_clear_dirty_pt_masked(struct kvm *kvm,
{
struct kvm_rmap_head *rmap_head;

+ if (kvm->arch.tdp_mmu_enabled)
+ kvm_tdp_mmu_clear_dirty_pt_masked(kvm, slot,
+ slot->base_gfn + gfn_offset, mask, false);
while (mask) {
rmap_head = __gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
PG_LEVEL_4K, slot);
@@ -5954,6 +5960,8 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
spin_lock(&kvm->mmu_lock);
flush = slot_handle_level(kvm, memslot, slot_rmap_write_protect,
start_level, KVM_MAX_HUGEPAGE_LEVEL, false);
+ if (kvm->arch.tdp_mmu_enabled)
+ flush = kvm_tdp_mmu_wrprot_slot(kvm, memslot, false) || flush;
spin_unlock(&kvm->mmu_lock);

/*
@@ -6034,6 +6042,7 @@ void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
kvm_flush_remote_tlbs_with_address(kvm, memslot->base_gfn,
memslot->npages);
}
+EXPORT_SYMBOL_GPL(kvm_arch_flush_remote_tlbs_memslot);

void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
struct kvm_memory_slot *memslot)
@@ -6042,6 +6051,8 @@ void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,

spin_lock(&kvm->mmu_lock);
flush = slot_handle_leaf(kvm, memslot, __rmap_clear_dirty, false);
+ if (kvm->arch.tdp_mmu_enabled)
+ flush = kvm_tdp_mmu_clear_dirty_slot(kvm, memslot) || flush;
spin_unlock(&kvm->mmu_lock);

/*
@@ -6063,6 +6074,8 @@ void kvm_mmu_slot_largepage_remove_write_access(struct kvm *kvm,
spin_lock(&kvm->mmu_lock);
flush = slot_handle_large_level(kvm, memslot, slot_rmap_write_protect,
false);
+ if (kvm->arch.tdp_mmu_enabled)
+ flush = kvm_tdp_mmu_wrprot_slot(kvm, memslot, true) || flush;
spin_unlock(&kvm->mmu_lock);

if (flush)
@@ -6077,6 +6090,8 @@ void kvm_mmu_slot_set_dirty(struct kvm *kvm,

spin_lock(&kvm->mmu_lock);
flush = slot_handle_all_level(kvm, memslot, __rmap_set_dirty, false);
+ if (kvm->arch.tdp_mmu_enabled)
+ flush = kvm_tdp_mmu_slot_set_dirty(kvm, memslot) || flush;
spin_unlock(&kvm->mmu_lock);

if (flush)
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 8eaa6e4764bce..1a777ccfde44e 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -89,6 +89,7 @@ bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
extern u64 shadow_user_mask;
extern u64 shadow_accessed_mask;
extern u64 shadow_present_mask;
+extern u64 shadow_dirty_mask;

#define ACC_EXEC_MASK 1
#define ACC_WRITE_MASK PT_WRITABLE_MASK
@@ -112,6 +113,7 @@ bool is_access_track_spte(u64 spte);
bool is_accessed_spte(u64 spte);
bool spte_ad_enabled(u64 spte);
bool is_executable_pte(u64 spte);
+bool spte_ad_need_write_protect(u64 spte);

void kvm_flush_remote_tlbs_with_address(struct kvm *kvm, u64 start_gfn,
u64 pages);
diff --git a/arch/x86/kvm/mmu/tdp_iter.c b/arch/x86/kvm/mmu/tdp_iter.c
index 6c1a38429c81a..132e286150856 100644
--- a/arch/x86/kvm/mmu/tdp_iter.c
+++ b/arch/x86/kvm/mmu/tdp_iter.c
@@ -178,3 +178,21 @@ void tdp_iter_refresh_walk(struct tdp_iter *iter)
tdp_iter_start(iter, iter->pt_path[iter->root_level - 1],
iter->root_level, goal_gfn);
}
+
+/*
+ * Move on to the next SPTE, but do not move down into a child page table even
+ * if the current SPTE leads to one.
+ */
+void tdp_iter_next_no_step_down(struct tdp_iter *iter)
+{
+ bool done;
+
+ done = try_step_side(iter);
+ while (!done) {
+ if (!try_step_up(iter)) {
+ iter->valid = false;
+ break;
+ }
+ done = try_step_side(iter);
+ }
+}
diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h
index 34da3bdada436..d0e65a62ea7d9 100644
--- a/arch/x86/kvm/mmu/tdp_iter.h
+++ b/arch/x86/kvm/mmu/tdp_iter.h
@@ -50,5 +50,6 @@ void tdp_iter_start(struct tdp_iter *iter, u64 *root_pt, int root_level,
gfn_t goal_gfn);
void tdp_iter_next(struct tdp_iter *iter);
void tdp_iter_refresh_walk(struct tdp_iter *iter);
+void tdp_iter_next_no_step_down(struct tdp_iter *iter);

#endif /* __KVM_X86_MMU_TDP_ITER_H */
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index bbe973d3f8084..e5cb7f0ec23e8 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -700,6 +700,7 @@ static int age_gfn_range(struct kvm *kvm, struct kvm_memory_slot *slot,

new_spte = mark_spte_for_access_track(new_spte);
}
+ new_spte &= ~shadow_dirty_mask;

*iter.sptep = new_spte;
__handle_changed_spte(kvm, as_id, iter.gfn, iter.old_spte,
@@ -804,3 +805,297 @@ int kvm_tdp_mmu_set_spte_hva(struct kvm *kvm, unsigned long address,
set_tdp_spte);
}

+/*
+ * Remove write access from all the SPTEs mapping GFNs [start, end). If
+ * skip_4k is set, SPTEs that map 4k pages, will not be write-protected.
+ * Returns true if an SPTE has been changed and the TLBs need to be flushed.
+ */
+static bool wrprot_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
+ gfn_t start, gfn_t end, bool skip_4k)
+{
+ struct tdp_iter iter;
+ u64 new_spte;
+ bool spte_set = false;
+ int as_id = kvm_mmu_page_as_id(root);
+
+ for_each_tdp_pte_root(iter, root, start, end) {
+iteration_start:
+ if (!is_shadow_present_pte(iter.old_spte))
+ continue;
+
+ /*
+ * If this entry points to a page of 4K entries, and 4k entries
+ * should be skipped, skip the whole page. If the non-leaf
+ * entry is at a higher level, move on to the next,
+ * (lower level) entry.
+ */
+ if (!is_last_spte(iter.old_spte, iter.level)) {
+ if (skip_4k && iter.level == PG_LEVEL_2M) {
+ tdp_iter_next_no_step_down(&iter);
+ if (iter.valid && iter.gfn >= end)
+ goto iteration_start;
+ else
+ break;
+ } else {
+ continue;
+ }
+ }
+
+ WARN_ON(skip_4k && iter.level == PG_LEVEL_4K);
+
+ new_spte = iter.old_spte & ~PT_WRITABLE_MASK;
+
+ *iter.sptep = new_spte;
+ __handle_changed_spte(kvm, as_id, iter.gfn, iter.old_spte,
+ new_spte, iter.level);
+ handle_changed_spte_acc_track(iter.old_spte, new_spte,
+ iter.level);
+ spte_set = true;
+
+ tdp_mmu_iter_cond_resched(kvm, &iter);
+ }
+ return spte_set;
+}
+
+/*
+ * Remove write access from all the SPTEs mapping GFNs in the memslot. If
+ * skip_4k is set, SPTEs that map 4k pages, will not be write-protected.
+ * Returns true if an SPTE has been changed and the TLBs need to be flushed.
+ */
+bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm, struct kvm_memory_slot *slot,
+ bool skip_4k)
+{
+ struct kvm_mmu_page *root;
+ int root_as_id;
+ bool spte_set = false;
+
+ for_each_tdp_mmu_root(kvm, root) {
+ root_as_id = kvm_mmu_page_as_id(root);
+ if (root_as_id != slot->as_id)
+ continue;
+
+ /*
+ * Take a reference on the root so that it cannot be freed if
+ * this thread releases the MMU lock and yields in this loop.
+ */
+ get_tdp_mmu_root(kvm, root);
+
+ spte_set = wrprot_gfn_range(kvm, root, slot->base_gfn,
+ slot->base_gfn + slot->npages, skip_4k) ||
+ spte_set;
+
+ put_tdp_mmu_root(kvm, root);
+ }
+
+ return spte_set;
+}
+
+/*
+ * Clear the dirty status of all the SPTEs mapping GFNs in the memslot. If
+ * AD bits are enabled, this will involve clearing the dirty bit on each SPTE.
+ * If AD bits are not enabled, this will require clearing the writable bit on
+ * each SPTE. Returns true if an SPTE has been changed and the TLBs need to
+ * be flushed.
+ */
+static bool clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
+ gfn_t start, gfn_t end)
+{
+ struct tdp_iter iter;
+ u64 new_spte;
+ bool spte_set = false;
+ int as_id = kvm_mmu_page_as_id(root);
+
+ for_each_tdp_pte_root(iter, root, start, end) {
+ if (!is_shadow_present_pte(iter.old_spte) ||
+ !is_last_spte(iter.old_spte, iter.level))
+ continue;
+
+ if (spte_ad_need_write_protect(iter.old_spte)) {
+ if (is_writable_pte(iter.old_spte))
+ new_spte = iter.old_spte & ~PT_WRITABLE_MASK;
+ else
+ continue;
+ } else {
+ if (iter.old_spte & shadow_dirty_mask)
+ new_spte = iter.old_spte & ~shadow_dirty_mask;
+ else
+ continue;
+ }
+
+ *iter.sptep = new_spte;
+ __handle_changed_spte(kvm, as_id, iter.gfn, iter.old_spte,
+ new_spte, iter.level);
+ handle_changed_spte_acc_track(iter.old_spte, new_spte,
+ iter.level);
+ spte_set = true;
+
+ tdp_mmu_iter_cond_resched(kvm, &iter);
+ }
+ return spte_set;
+}
+
+/*
+ * Clear the dirty status of all the SPTEs mapping GFNs in the memslot. If
+ * AD bits are enabled, this will involve clearing the dirty bit on each SPTE.
+ * If AD bits are not enabled, this will require clearing the writable bit on
+ * each SPTE. Returns true if an SPTE has been changed and the TLBs need to
+ * be flushed.
+ */
+bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ struct kvm_mmu_page *root;
+ int root_as_id;
+ bool spte_set = false;
+
+ for_each_tdp_mmu_root(kvm, root) {
+ root_as_id = kvm_mmu_page_as_id(root);
+ if (root_as_id != slot->as_id)
+ continue;
+
+ /*
+ * Take a reference on the root so that it cannot be freed if
+ * this thread releases the MMU lock and yields in this loop.
+ */
+ get_tdp_mmu_root(kvm, root);
+
+ spte_set = clear_dirty_gfn_range(kvm, root, slot->base_gfn,
+ slot->base_gfn + slot->npages) || spte_set;
+
+ put_tdp_mmu_root(kvm, root);
+ }
+
+ return spte_set;
+}
+
+/*
+ * Clears the dirty status of all the 4k SPTEs mapping GFNs for which a bit is
+ * set in mask, starting at gfn. The given memslot is expected to contain all
+ * the GFNs represented by set bits in the mask. If AD bits are enabled,
+ * clearing the dirty status will involve clearing the dirty bit on each SPTE
+ * or, if AD bits are not enabled, clearing the writable bit on each SPTE.
+ */
+static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root,
+ gfn_t gfn, unsigned long mask, bool wrprot)
+{
+ struct tdp_iter iter;
+ u64 new_spte;
+ int as_id = kvm_mmu_page_as_id(root);
+
+ for_each_tdp_pte_root(iter, root, gfn + __ffs(mask),
+ gfn + BITS_PER_LONG) {
+ if (!mask)
+ break;
+
+ if (!is_shadow_present_pte(iter.old_spte) ||
+ !is_last_spte(iter.old_spte, iter.level) ||
+ iter.level > PG_LEVEL_4K ||
+ !(mask & (1UL << (iter.gfn - gfn))))
+ continue;
+
+ if (wrprot || spte_ad_need_write_protect(iter.old_spte)) {
+ if (is_writable_pte(iter.old_spte))
+ new_spte = iter.old_spte & ~PT_WRITABLE_MASK;
+ else
+ continue;
+ } else {
+ if (iter.old_spte & shadow_dirty_mask)
+ new_spte = iter.old_spte & ~shadow_dirty_mask;
+ else
+ continue;
+ }
+
+ *iter.sptep = new_spte;
+ __handle_changed_spte(kvm, as_id, iter.gfn, iter.old_spte,
+ new_spte, iter.level);
+ handle_changed_spte_acc_track(iter.old_spte, new_spte,
+ iter.level);
+
+ mask &= ~(1UL << (iter.gfn - gfn));
+ }
+}
+
+/*
+ * Clears the dirty status of all the 4k SPTEs mapping GFNs for which a bit is
+ * set in mask, starting at gfn. The given memslot is expected to contain all
+ * the GFNs represented by set bits in the mask. If AD bits are enabled,
+ * clearing the dirty status will involve clearing the dirty bit on each SPTE
+ * or, if AD bits are not enabled, clearing the writable bit on each SPTE.
+ */
+void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm,
+ struct kvm_memory_slot *slot,
+ gfn_t gfn, unsigned long mask,
+ bool wrprot)
+{
+ struct kvm_mmu_page *root;
+ int root_as_id;
+
+ lockdep_assert_held(&kvm->mmu_lock);
+ for_each_tdp_mmu_root(kvm, root) {
+ root_as_id = kvm_mmu_page_as_id(root);
+ if (root_as_id != slot->as_id)
+ continue;
+
+ clear_dirty_pt_masked(kvm, root, gfn, mask, wrprot);
+ }
+}
+
+/*
+ * Set the dirty status of all the SPTEs mapping GFNs in the memslot. This is
+ * only used for PML, and so will involve setting the dirty bit on each SPTE.
+ * Returns true if an SPTE has been changed and the TLBs need to be flushed.
+ */
+static bool set_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
+ gfn_t start, gfn_t end)
+{
+ struct tdp_iter iter;
+ u64 new_spte;
+ bool spte_set = false;
+ int as_id = kvm_mmu_page_as_id(root);
+
+ for_each_tdp_pte_root(iter, root, start, end) {
+ if (!is_shadow_present_pte(iter.old_spte))
+ continue;
+
+ new_spte = iter.old_spte | shadow_dirty_mask;
+
+ *iter.sptep = new_spte;
+ handle_changed_spte(kvm, as_id, iter.gfn, iter.old_spte,
+ new_spte, iter.level);
+ spte_set = true;
+
+ tdp_mmu_iter_cond_resched(kvm, &iter);
+ }
+
+ return spte_set;
+}
+
+/*
+ * Set the dirty status of all the SPTEs mapping GFNs in the memslot. This is
+ * only used for PML, and so will involve setting the dirty bit on each SPTE.
+ * Returns true if an SPTE has been changed and the TLBs need to be flushed.
+ */
+bool kvm_tdp_mmu_slot_set_dirty(struct kvm *kvm, struct kvm_memory_slot *slot)
+{
+ struct kvm_mmu_page *root;
+ int root_as_id;
+ bool spte_set = false;
+
+ for_each_tdp_mmu_root(kvm, root) {
+ root_as_id = kvm_mmu_page_as_id(root);
+ if (root_as_id != slot->as_id)
+ continue;
+
+ /*
+ * Take a reference on the root so that it cannot be freed if
+ * this thread releases the MMU lock and yields in this loop.
+ */
+ get_tdp_mmu_root(kvm, root);
+
+ spte_set = set_dirty_gfn_range(kvm, root, slot->base_gfn,
+ slot->base_gfn + slot->npages) || spte_set;
+
+ put_tdp_mmu_root(kvm, root);
+ }
+ return spte_set;
+}
+
diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
index 5a399aa60b8d8..2c9322ba3462b 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.h
+++ b/arch/x86/kvm/mmu/tdp_mmu.h
@@ -28,4 +28,14 @@ int kvm_tdp_mmu_test_age_hva(struct kvm *kvm, unsigned long hva);

int kvm_tdp_mmu_set_spte_hva(struct kvm *kvm, unsigned long address,
pte_t *host_ptep);
+
+bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm, struct kvm_memory_slot *slot,
+ bool skip_4k);
+bool kvm_tdp_mmu_clear_dirty_slot(struct kvm *kvm,
+ struct kvm_memory_slot *slot);
+void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm,
+ struct kvm_memory_slot *slot,
+ gfn_t gfn, unsigned long mask,
+ bool wrprot);
+bool kvm_tdp_mmu_slot_set_dirty(struct kvm *kvm, struct kvm_memory_slot *slot);
#endif /* __KVM_X86_MMU_TDP_MMU_H */
--
2.28.0.709.gb0816b6eb0-goog
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