aboutsummaryrefslogtreecommitdiff
path: root/arch/x86/kvm/mmu.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/kvm/mmu.c')
-rw-r--r--arch/x86/kvm/mmu.c345
1 files changed, 197 insertions, 148 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 4cb16426884..72102e0ab7c 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -135,8 +135,6 @@ module_param(dbg, bool, 0644);
#define PT64_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | PT_USER_MASK \
| PT64_NX_MASK)
-#define PTE_LIST_EXT 4
-
#define ACC_EXEC_MASK 1
#define ACC_WRITE_MASK PT_WRITABLE_MASK
#define ACC_USER_MASK PT_USER_MASK
@@ -151,6 +149,9 @@ module_param(dbg, bool, 0644);
#define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
+/* make pte_list_desc fit well in cache line */
+#define PTE_LIST_EXT 3
+
struct pte_list_desc {
u64 *sptes[PTE_LIST_EXT];
struct pte_list_desc *more;
@@ -550,19 +551,29 @@ static u64 mmu_spte_get_lockless(u64 *sptep)
static void walk_shadow_page_lockless_begin(struct kvm_vcpu *vcpu)
{
- rcu_read_lock();
- atomic_inc(&vcpu->kvm->arch.reader_counter);
-
- /* Increase the counter before walking shadow page table */
- smp_mb__after_atomic_inc();
+ /*
+ * Prevent page table teardown by making any free-er wait during
+ * kvm_flush_remote_tlbs() IPI to all active vcpus.
+ */
+ local_irq_disable();
+ vcpu->mode = READING_SHADOW_PAGE_TABLES;
+ /*
+ * Make sure a following spte read is not reordered ahead of the write
+ * to vcpu->mode.
+ */
+ smp_mb();
}
static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu)
{
- /* Decrease the counter after walking shadow page table finished */
- smp_mb__before_atomic_dec();
- atomic_dec(&vcpu->kvm->arch.reader_counter);
- rcu_read_unlock();
+ /*
+ * Make sure the write to vcpu->mode is not reordered in front of
+ * reads to sptes. If it does, kvm_commit_zap_page() can see us
+ * OUTSIDE_GUEST_MODE and proceed to free the shadow page table.
+ */
+ smp_mb();
+ vcpu->mode = OUTSIDE_GUEST_MODE;
+ local_irq_enable();
}
static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
@@ -841,32 +852,6 @@ static int pte_list_add(struct kvm_vcpu *vcpu, u64 *spte,
return count;
}
-static u64 *pte_list_next(unsigned long *pte_list, u64 *spte)
-{
- struct pte_list_desc *desc;
- u64 *prev_spte;
- int i;
-
- if (!*pte_list)
- return NULL;
- else if (!(*pte_list & 1)) {
- if (!spte)
- return (u64 *)*pte_list;
- return NULL;
- }
- desc = (struct pte_list_desc *)(*pte_list & ~1ul);
- prev_spte = NULL;
- while (desc) {
- for (i = 0; i < PTE_LIST_EXT && desc->sptes[i]; ++i) {
- if (prev_spte == spte)
- return desc->sptes[i];
- prev_spte = desc->sptes[i];
- }
- desc = desc->more;
- }
- return NULL;
-}
-
static void
pte_list_desc_remove_entry(unsigned long *pte_list, struct pte_list_desc *desc,
int i, struct pte_list_desc *prev_desc)
@@ -987,11 +972,6 @@ static int rmap_add(struct kvm_vcpu *vcpu, u64 *spte, gfn_t gfn)
return pte_list_add(vcpu, spte, rmapp);
}
-static u64 *rmap_next(unsigned long *rmapp, u64 *spte)
-{
- return pte_list_next(rmapp, spte);
-}
-
static void rmap_remove(struct kvm *kvm, u64 *spte)
{
struct kvm_mmu_page *sp;
@@ -1004,106 +984,201 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
pte_list_remove(spte, rmapp);
}
+/*
+ * Used by the following functions to iterate through the sptes linked by a
+ * rmap. All fields are private and not assumed to be used outside.
+ */
+struct rmap_iterator {
+ /* private fields */
+ struct pte_list_desc *desc; /* holds the sptep if not NULL */
+ int pos; /* index of the sptep */
+};
+
+/*
+ * Iteration must be started by this function. This should also be used after
+ * removing/dropping sptes from the rmap link because in such cases the
+ * information in the itererator may not be valid.
+ *
+ * Returns sptep if found, NULL otherwise.
+ */
+static u64 *rmap_get_first(unsigned long rmap, struct rmap_iterator *iter)
+{
+ if (!rmap)
+ return NULL;
+
+ if (!(rmap & 1)) {
+ iter->desc = NULL;
+ return (u64 *)rmap;
+ }
+
+ iter->desc = (struct pte_list_desc *)(rmap & ~1ul);
+ iter->pos = 0;
+ return iter->desc->sptes[iter->pos];
+}
+
+/*
+ * Must be used with a valid iterator: e.g. after rmap_get_first().
+ *
+ * Returns sptep if found, NULL otherwise.
+ */
+static u64 *rmap_get_next(struct rmap_iterator *iter)
+{
+ if (iter->desc) {
+ if (iter->pos < PTE_LIST_EXT - 1) {
+ u64 *sptep;
+
+ ++iter->pos;
+ sptep = iter->desc->sptes[iter->pos];
+ if (sptep)
+ return sptep;
+ }
+
+ iter->desc = iter->desc->more;
+
+ if (iter->desc) {
+ iter->pos = 0;
+ /* desc->sptes[0] cannot be NULL */
+ return iter->desc->sptes[iter->pos];
+ }
+ }
+
+ return NULL;
+}
+
static void drop_spte(struct kvm *kvm, u64 *sptep)
{
if (mmu_spte_clear_track_bits(sptep))
rmap_remove(kvm, sptep);
}
-int kvm_mmu_rmap_write_protect(struct kvm *kvm, u64 gfn,
- struct kvm_memory_slot *slot)
+static int __rmap_write_protect(struct kvm *kvm, unsigned long *rmapp, int level)
{
- unsigned long *rmapp;
- u64 *spte;
- int i, write_protected = 0;
-
- rmapp = __gfn_to_rmap(gfn, PT_PAGE_TABLE_LEVEL, slot);
- spte = rmap_next(rmapp, NULL);
- while (spte) {
- BUG_ON(!(*spte & PT_PRESENT_MASK));
- rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
- if (is_writable_pte(*spte)) {
- mmu_spte_update(spte, *spte & ~PT_WRITABLE_MASK);
- write_protected = 1;
+ u64 *sptep;
+ struct rmap_iterator iter;
+ int write_protected = 0;
+
+ for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
+ BUG_ON(!(*sptep & PT_PRESENT_MASK));
+ rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep);
+
+ if (!is_writable_pte(*sptep)) {
+ sptep = rmap_get_next(&iter);
+ continue;
}
- spte = rmap_next(rmapp, spte);
- }
- /* check for huge page mappings */
- for (i = PT_DIRECTORY_LEVEL;
- i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
- rmapp = __gfn_to_rmap(gfn, i, slot);
- spte = rmap_next(rmapp, NULL);
- while (spte) {
- BUG_ON(!(*spte & PT_PRESENT_MASK));
- BUG_ON(!is_large_pte(*spte));
- pgprintk("rmap_write_protect(large): spte %p %llx %lld\n", spte, *spte, gfn);
- if (is_writable_pte(*spte)) {
- drop_spte(kvm, spte);
- --kvm->stat.lpages;
- spte = NULL;
- write_protected = 1;
- }
- spte = rmap_next(rmapp, spte);
+ if (level == PT_PAGE_TABLE_LEVEL) {
+ mmu_spte_update(sptep, *sptep & ~PT_WRITABLE_MASK);
+ sptep = rmap_get_next(&iter);
+ } else {
+ BUG_ON(!is_large_pte(*sptep));
+ drop_spte(kvm, sptep);
+ --kvm->stat.lpages;
+ sptep = rmap_get_first(*rmapp, &iter);
}
+
+ write_protected = 1;
}
return write_protected;
}
+/**
+ * kvm_mmu_write_protect_pt_masked - write protect selected PT level pages
+ * @kvm: kvm instance
+ * @slot: slot to protect
+ * @gfn_offset: start of the BITS_PER_LONG pages we care about
+ * @mask: indicates which pages we should protect
+ *
+ * Used when we do not need to care about huge page mappings: e.g. during dirty
+ * logging we do not have any such mappings.
+ */
+void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
+ struct kvm_memory_slot *slot,
+ gfn_t gfn_offset, unsigned long mask)
+{
+ unsigned long *rmapp;
+
+ while (mask) {
+ rmapp = &slot->rmap[gfn_offset + __ffs(mask)];
+ __rmap_write_protect(kvm, rmapp, PT_PAGE_TABLE_LEVEL);
+
+ /* clear the first set bit */
+ mask &= mask - 1;
+ }
+}
+
static int rmap_write_protect(struct kvm *kvm, u64 gfn)
{
struct kvm_memory_slot *slot;
+ unsigned long *rmapp;
+ int i;
+ int write_protected = 0;
slot = gfn_to_memslot(kvm, gfn);
- return kvm_mmu_rmap_write_protect(kvm, gfn, slot);
+
+ for (i = PT_PAGE_TABLE_LEVEL;
+ i < PT_PAGE_TABLE_LEVEL + KVM_NR_PAGE_SIZES; ++i) {
+ rmapp = __gfn_to_rmap(gfn, i, slot);
+ write_protected |= __rmap_write_protect(kvm, rmapp, i);
+ }
+
+ return write_protected;
}
static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long data)
{
- u64 *spte;
+ u64 *sptep;
+ struct rmap_iterator iter;
int need_tlb_flush = 0;
- while ((spte = rmap_next(rmapp, NULL))) {
- BUG_ON(!(*spte & PT_PRESENT_MASK));
- rmap_printk("kvm_rmap_unmap_hva: spte %p %llx\n", spte, *spte);
- drop_spte(kvm, spte);
+ while ((sptep = rmap_get_first(*rmapp, &iter))) {
+ BUG_ON(!(*sptep & PT_PRESENT_MASK));
+ rmap_printk("kvm_rmap_unmap_hva: spte %p %llx\n", sptep, *sptep);
+
+ drop_spte(kvm, sptep);
need_tlb_flush = 1;
}
+
return need_tlb_flush;
}
static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long data)
{
+ u64 *sptep;
+ struct rmap_iterator iter;
int need_flush = 0;
- u64 *spte, new_spte;
+ u64 new_spte;
pte_t *ptep = (pte_t *)data;
pfn_t new_pfn;
WARN_ON(pte_huge(*ptep));
new_pfn = pte_pfn(*ptep);
- spte = rmap_next(rmapp, NULL);
- while (spte) {
- BUG_ON(!is_shadow_present_pte(*spte));
- rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n", spte, *spte);
+
+ for (sptep = rmap_get_first(*rmapp, &iter); sptep;) {
+ BUG_ON(!is_shadow_present_pte(*sptep));
+ rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n", sptep, *sptep);
+
need_flush = 1;
+
if (pte_write(*ptep)) {
- drop_spte(kvm, spte);
- spte = rmap_next(rmapp, NULL);
+ drop_spte(kvm, sptep);
+ sptep = rmap_get_first(*rmapp, &iter);
} else {
- new_spte = *spte &~ (PT64_BASE_ADDR_MASK);
+ new_spte = *sptep & ~PT64_BASE_ADDR_MASK;
new_spte |= (u64)new_pfn << PAGE_SHIFT;
new_spte &= ~PT_WRITABLE_MASK;
new_spte &= ~SPTE_HOST_WRITEABLE;
new_spte &= ~shadow_accessed_mask;
- mmu_spte_clear_track_bits(spte);
- mmu_spte_set(spte, new_spte);
- spte = rmap_next(rmapp, spte);
+
+ mmu_spte_clear_track_bits(sptep);
+ mmu_spte_set(sptep, new_spte);
+ sptep = rmap_get_next(&iter);
}
}
+
if (need_flush)
kvm_flush_remote_tlbs(kvm);
@@ -1162,7 +1237,8 @@ void kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long data)
{
- u64 *spte;
+ u64 *sptep;
+ struct rmap_iterator iter;
int young = 0;
/*
@@ -1175,25 +1251,24 @@ static int kvm_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
if (!shadow_accessed_mask)
return kvm_unmap_rmapp(kvm, rmapp, data);
- spte = rmap_next(rmapp, NULL);
- while (spte) {
- int _young;
- u64 _spte = *spte;
- BUG_ON(!(_spte & PT_PRESENT_MASK));
- _young = _spte & PT_ACCESSED_MASK;
- if (_young) {
+ for (sptep = rmap_get_first(*rmapp, &iter); sptep;
+ sptep = rmap_get_next(&iter)) {
+ BUG_ON(!(*sptep & PT_PRESENT_MASK));
+
+ if (*sptep & PT_ACCESSED_MASK) {
young = 1;
- clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte);
+ clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)sptep);
}
- spte = rmap_next(rmapp, spte);
}
+
return young;
}
static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
unsigned long data)
{
- u64 *spte;
+ u64 *sptep;
+ struct rmap_iterator iter;
int young = 0;
/*
@@ -1204,16 +1279,14 @@ static int kvm_test_age_rmapp(struct kvm *kvm, unsigned long *rmapp,
if (!shadow_accessed_mask)
goto out;
- spte = rmap_next(rmapp, NULL);
- while (spte) {
- u64 _spte = *spte;
- BUG_ON(!(_spte & PT_PRESENT_MASK));
- young = _spte & PT_ACCESSED_MASK;
- if (young) {
+ for (sptep = rmap_get_first(*rmapp, &iter); sptep;
+ sptep = rmap_get_next(&iter)) {
+ BUG_ON(!(*sptep & PT_PRESENT_MASK));
+
+ if (*sptep & PT_ACCESSED_MASK) {
young = 1;
break;
}
- spte = rmap_next(rmapp, spte);
}
out:
return young;
@@ -1865,10 +1938,11 @@ static void kvm_mmu_put_page(struct kvm_mmu_page *sp, u64 *parent_pte)
static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
{
- u64 *parent_pte;
+ u64 *sptep;
+ struct rmap_iterator iter;
- while ((parent_pte = pte_list_next(&sp->parent_ptes, NULL)))
- drop_parent_pte(sp, parent_pte);
+ while ((sptep = rmap_get_first(sp->parent_ptes, &iter)))
+ drop_parent_pte(sp, sptep);
}
static int mmu_zap_unsync_children(struct kvm *kvm,
@@ -1925,30 +1999,6 @@ static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
return ret;
}
-static void kvm_mmu_isolate_pages(struct list_head *invalid_list)
-{
- struct kvm_mmu_page *sp;
-
- list_for_each_entry(sp, invalid_list, link)
- kvm_mmu_isolate_page(sp);
-}
-
-static void free_pages_rcu(struct rcu_head *head)
-{
- struct kvm_mmu_page *next, *sp;
-
- sp = container_of(head, struct kvm_mmu_page, rcu);
- while (sp) {
- if (!list_empty(&sp->link))
- next = list_first_entry(&sp->link,
- struct kvm_mmu_page, link);
- else
- next = NULL;
- kvm_mmu_free_page(sp);
- sp = next;
- }
-}
-
static void kvm_mmu_commit_zap_page(struct kvm *kvm,
struct list_head *invalid_list)
{
@@ -1957,17 +2007,17 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
if (list_empty(invalid_list))
return;
- kvm_flush_remote_tlbs(kvm);
-
- if (atomic_read(&kvm->arch.reader_counter)) {
- kvm_mmu_isolate_pages(invalid_list);
- sp = list_first_entry(invalid_list, struct kvm_mmu_page, link);
- list_del_init(invalid_list);
+ /*
+ * wmb: make sure everyone sees our modifications to the page tables
+ * rmb: make sure we see changes to vcpu->mode
+ */
+ smp_mb();
- trace_kvm_mmu_delay_free_pages(sp);
- call_rcu(&sp->rcu, free_pages_rcu);
- return;
- }
+ /*
+ * Wait for all vcpus to exit guest mode and/or lockless shadow
+ * page table walks.
+ */
+ kvm_flush_remote_tlbs(kvm);
do {
sp = list_first_entry(invalid_list, struct kvm_mmu_page, link);
@@ -1975,7 +2025,6 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
kvm_mmu_isolate_page(sp);
kvm_mmu_free_page(sp);
} while (!list_empty(invalid_list));
-
}
/*
@@ -3554,7 +3603,7 @@ static bool detect_write_flooding(struct kvm_mmu_page *sp)
* Skip write-flooding detected for the sp whose level is 1, because
* it can become unsync, then the guest page is not write-protected.
*/
- if (sp->role.level == 1)
+ if (sp->role.level == PT_PAGE_TABLE_LEVEL)
return false;
return ++sp->write_flooding_count >= 3;