[PATCH] KVM: cleanup allocation of rmaps and page tracking data
From: Paolo Bonzini
Date: Mon Oct 18 2021 - 13:53:44 EST
From: David Stevens <stevensd@xxxxxxxxxxxx>
Unify the flags for rmaps and page tracking data, using a
single flag in struct kvm_arch and a single loop to go
over all the address spaces and memslots. This avoids
code duplication between alloc_all_memslots_rmaps and
kvm_page_track_enable_mmu_write_tracking.
Signed-off-by: David Stevens <stevensd@xxxxxxxxxxxx>
[This patch is the delta between David's v2 and v3, with conflicts
fixed and my own commit message. - Paolo]
Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 17 ++----
arch/x86/include/asm/kvm_page_track.h | 3 +-
arch/x86/kvm/mmu.h | 16 ++++--
arch/x86/kvm/mmu/mmu.c | 78 +++++++++++++++++++++------
arch/x86/kvm/mmu/page_track.c | 59 ++++++--------------
arch/x86/kvm/x86.c | 47 +---------------
6 files changed, 97 insertions(+), 123 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 88f0326c184a..80f4b8a9233c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1212,18 +1212,11 @@ struct kvm_arch {
#endif /* CONFIG_X86_64 */
/*
- * If set, rmaps have been allocated for all memslots and should be
- * allocated for any newly created or modified memslots.
+ * If set, at least one shadow root has been allocated. This flag
+ * is used as one input when determining whether certain memslot
+ * related allocations are necessary.
*/
- bool memslots_have_rmaps;
-
- /*
- * Set when the KVM mmu needs guest write access page tracking. If
- * set, the necessary gfn_track arrays have been allocated for
- * all memslots and should be allocated for any newly created or
- * modified memslots.
- */
- bool memslots_mmu_write_tracking;
+ bool shadow_root_alloced;
#if IS_ENABLED(CONFIG_HYPERV)
hpa_t hv_root_tdp;
@@ -1946,7 +1939,7 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
int kvm_cpu_dirty_log_size(void);
-int alloc_all_memslots_rmaps(struct kvm *kvm);
+int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages);
#define KVM_CLOCK_VALID_FLAGS \
(KVM_CLOCK_TSC_STABLE | KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC)
diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
index 79d84a94f8eb..9d4a3b1b25b9 100644
--- a/arch/x86/include/asm/kvm_page_track.h
+++ b/arch/x86/include/asm/kvm_page_track.h
@@ -49,7 +49,8 @@ struct kvm_page_track_notifier_node {
int kvm_page_track_init(struct kvm *kvm);
void kvm_page_track_cleanup(struct kvm *kvm);
-int kvm_page_track_enable_mmu_write_tracking(struct kvm *kvm);
+bool kvm_page_track_write_tracking_enabled(struct kvm *kvm);
+int kvm_page_track_write_tracking_alloc(struct kvm_memory_slot *slot);
void kvm_page_track_free_memslot(struct kvm_memory_slot *slot);
int kvm_page_track_create_memslot(struct kvm *kvm,
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index e53ef2ae958f..1ae70efedcf4 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -303,14 +303,20 @@ int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu);
int kvm_mmu_post_init_vm(struct kvm *kvm);
void kvm_mmu_pre_destroy_vm(struct kvm *kvm);
-static inline bool kvm_memslots_have_rmaps(struct kvm *kvm)
+static inline bool kvm_shadow_root_alloced(struct kvm *kvm)
{
/*
- * Read memslot_have_rmaps before rmap pointers. Hence, threads reading
- * memslots_have_rmaps in any lock context are guaranteed to see the
- * pointers. Pairs with smp_store_release in alloc_all_memslots_rmaps.
+ * Read shadow_root_alloced before related pointers. Hence, threads
+ * reading shadow_root_alloced in any lock context are guaranteed to
+ * see the pointers. Pairs with smp_store_release in
+ * mmu_first_shadow_root_alloc.
*/
- return smp_load_acquire(&kvm->arch.memslots_have_rmaps);
+ return smp_load_acquire(&kvm->arch.shadow_root_alloced);
+}
+
+static inline bool kvm_memslots_have_rmaps(struct kvm *kvm)
+{
+ return !kvm->arch.tdp_mmu_enabled || kvm_shadow_root_alloced(kvm);
}
static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 29e7a4bb26e9..757e2a1ed149 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3397,6 +3397,67 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
return r;
}
+static int mmu_first_shadow_root_alloc(struct kvm *kvm)
+{
+ struct kvm_memslots *slots;
+ struct kvm_memory_slot *slot;
+ int r = 0, i;
+
+ /*
+ * Check if this is the first shadow root being allocated before
+ * taking the lock.
+ */
+ if (kvm_shadow_root_alloced(kvm))
+ return 0;
+
+ mutex_lock(&kvm->slots_arch_lock);
+
+ /* Recheck, under the lock, whether this is the first shadow root. */
+ if (kvm_shadow_root_alloced(kvm))
+ goto out_unlock;
+
+ /*
+ * Check if anything actually needs to be allocated, e.g. all metadata
+ * will be allocated upfront if TDP is disabled.
+ */
+ if (kvm_memslots_have_rmaps(kvm) &&
+ kvm_page_track_write_tracking_enabled(kvm))
+ goto out_success;
+
+ for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
+ slots = __kvm_memslots(kvm, i);
+ kvm_for_each_memslot(slot, slots) {
+ /*
+ * Both of these functions are no-ops if the target is
+ * already allocated, so unconditionally calling both
+ * is safe. Intentionally do NOT free allocations on
+ * failure to avoid having to track which allocations
+ * were made now versus when the memslot was created.
+ * The metadata is guaranteed to be freed when the slot
+ * is freed, and will be kept/used if userspace retries
+ * KVM_RUN instead of killing the VM.
+ */
+ r = memslot_rmap_alloc(slot, slot->npages);
+ if (r)
+ goto out_unlock;
+ r = kvm_page_track_write_tracking_alloc(slot);
+ if (r)
+ goto out_unlock;
+ }
+ }
+
+ /*
+ * Ensure that shadow_root_alloced becomes true strictly after
+ * all the related pointers are set.
+ */
+out_success:
+ smp_store_release(&kvm->arch.shadow_root_alloced, true);
+
+out_unlock:
+ mutex_unlock(&kvm->slots_arch_lock);
+ return r;
+}
+
static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
@@ -3427,11 +3488,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
}
}
- r = alloc_all_memslots_rmaps(vcpu->kvm);
- if (r)
- return r;
-
- r = kvm_page_track_enable_mmu_write_tracking(vcpu->kvm);
+ r = mmu_first_shadow_root_alloc(vcpu->kvm);
if (r)
return r;
@@ -5604,16 +5661,7 @@ void kvm_mmu_init_vm(struct kvm *kvm)
spin_lock_init(&kvm->arch.mmu_unsync_pages_lock);
- if (!kvm_mmu_init_tdp_mmu(kvm))
- /*
- * No smp_load/store wrappers needed here as we are in
- * VM init and there cannot be any memslots / other threads
- * accessing this struct kvm yet.
- */
- kvm->arch.memslots_have_rmaps = true;
-
- if (!tdp_enabled)
- kvm->arch.memslots_mmu_write_tracking = true;
+ kvm_mmu_init_tdp_mmu(kvm);
node->track_write = kvm_mmu_pte_write;
node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index 357605809825..5e0684460930 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -19,14 +19,10 @@
#include "mmu.h"
#include "mmu_internal.h"
-static bool write_tracking_enabled(struct kvm *kvm)
+bool kvm_page_track_write_tracking_enabled(struct kvm *kvm)
{
- /*
- * Read memslots_mmu_write_tracking before gfn_track pointers. Pairs
- * with smp_store_release in kvm_page_track_enable_mmu_write_tracking.
- */
return IS_ENABLED(CONFIG_KVM_EXTERNAL_WRITE_TRACKING) ||
- smp_load_acquire(&kvm->arch.memslots_mmu_write_tracking);
+ !tdp_enabled || kvm_shadow_root_alloced(kvm);
}
void kvm_page_track_free_memslot(struct kvm_memory_slot *slot)
@@ -46,7 +42,8 @@ int kvm_page_track_create_memslot(struct kvm *kvm,
int i;
for (i = 0; i < KVM_PAGE_TRACK_MAX; i++) {
- if (i == KVM_PAGE_TRACK_WRITE && !write_tracking_enabled(kvm))
+ if (i == KVM_PAGE_TRACK_WRITE &&
+ !kvm_page_track_write_tracking_enabled(kvm))
continue;
slot->arch.gfn_track[i] =
@@ -70,45 +67,18 @@ static inline bool page_track_mode_is_valid(enum kvm_page_track_mode mode)
return true;
}
-int kvm_page_track_enable_mmu_write_tracking(struct kvm *kvm)
+int kvm_page_track_write_tracking_alloc(struct kvm_memory_slot *slot)
{
- struct kvm_memslots *slots;
- struct kvm_memory_slot *slot;
- unsigned short **gfn_track;
- int i;
+ unsigned short *gfn_track;
- if (write_tracking_enabled(kvm))
+ if (slot->arch.gfn_track[KVM_PAGE_TRACK_WRITE])
return 0;
- mutex_lock(&kvm->slots_arch_lock);
-
- if (write_tracking_enabled(kvm)) {
- mutex_unlock(&kvm->slots_arch_lock);
- return 0;
- }
-
- for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
- slots = __kvm_memslots(kvm, i);
- kvm_for_each_memslot(slot, slots) {
- gfn_track = slot->arch.gfn_track + KVM_PAGE_TRACK_WRITE;
- if (*gfn_track)
- continue;
-
- *gfn_track = vcalloc(slot->npages, sizeof(**gfn_track));
- if (*gfn_track == NULL) {
- mutex_unlock(&kvm->slots_arch_lock);
- return -ENOMEM;
- }
- }
- }
-
- /*
- * Ensure that memslots_mmu_write_tracking becomes true strictly
- * after all the pointers are set.
- */
- smp_store_release(&kvm->arch.memslots_mmu_write_tracking, true);
- mutex_unlock(&kvm->slots_arch_lock);
+ gfn_track = vcalloc(slot->npages, sizeof(*gfn_track));
+ if (gfn_track == NULL)
+ return -ENOMEM;
+ slot->arch.gfn_track[KVM_PAGE_TRACK_WRITE] = gfn_track;
return 0;
}
@@ -148,7 +118,7 @@ void kvm_slot_page_track_add_page(struct kvm *kvm,
return;
if (WARN_ON(mode == KVM_PAGE_TRACK_WRITE &&
- !write_tracking_enabled(kvm)))
+ !kvm_page_track_write_tracking_enabled(kvm)))
return;
update_gfn_track(slot, gfn, mode, 1);
@@ -186,7 +156,7 @@ void kvm_slot_page_track_remove_page(struct kvm *kvm,
return;
if (WARN_ON(mode == KVM_PAGE_TRACK_WRITE &&
- !write_tracking_enabled(kvm)))
+ !kvm_page_track_write_tracking_enabled(kvm)))
return;
update_gfn_track(slot, gfn, mode, -1);
@@ -214,7 +184,8 @@ bool kvm_slot_page_track_is_active(struct kvm_vcpu *vcpu,
if (!slot)
return false;
- if (mode == KVM_PAGE_TRACK_WRITE && !write_tracking_enabled(vcpu->kvm))
+ if (mode == KVM_PAGE_TRACK_WRITE &&
+ !kvm_page_track_write_tracking_enabled(vcpu->kvm))
return false;
index = gfn_to_index(gfn, slot->base_gfn, PG_LEVEL_4K);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fce4d2eb69e6..b515a3d85a46 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11516,8 +11516,7 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
kvm_page_track_free_memslot(slot);
}
-static int memslot_rmap_alloc(struct kvm_memory_slot *slot,
- unsigned long npages)
+int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages)
{
const int sz = sizeof(*slot->arch.rmap[0]);
int i;
@@ -11539,50 +11538,6 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot,
return 0;
}
-int alloc_all_memslots_rmaps(struct kvm *kvm)
-{
- struct kvm_memslots *slots;
- struct kvm_memory_slot *slot;
- int r, i;
-
- /*
- * Check if memslots alreday have rmaps early before acquiring
- * the slots_arch_lock below.
- */
- if (kvm_memslots_have_rmaps(kvm))
- return 0;
-
- mutex_lock(&kvm->slots_arch_lock);
-
- /*
- * Read memslots_have_rmaps again, under the slots arch lock,
- * before allocating the rmaps
- */
- if (kvm_memslots_have_rmaps(kvm)) {
- mutex_unlock(&kvm->slots_arch_lock);
- return 0;
- }
-
- for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
- slots = __kvm_memslots(kvm, i);
- kvm_for_each_memslot(slot, slots) {
- r = memslot_rmap_alloc(slot, slot->npages);
- if (r) {
- mutex_unlock(&kvm->slots_arch_lock);
- return r;
- }
- }
- }
-
- /*
- * Ensure that memslots_have_rmaps becomes true strictly after
- * all the rmap pointers are set.
- */
- smp_store_release(&kvm->arch.memslots_have_rmaps, true);
- mutex_unlock(&kvm->slots_arch_lock);
- return 0;
-}
-
static int kvm_alloc_memslot_metadata(struct kvm *kvm,
struct kvm_memory_slot *slot,
unsigned long npages)
--
2.27.0