In order to allow multiple TDP MMU operations to proceed in parallel,
there must be an option to modify SPTEs atomically so that changes are
not lost. Add that option to __tdp_mmu_set_spte and
__handle_changed_spte.
Reviewed-by: Peter Feiner <pfei...@google.com>
Signed-off-by: Ben Gardon <bgar...@google.com>
---
arch/x86/kvm/mmu/tdp_mmu.c | 67 ++++++++++++++++++++++++++++++++------
1 file changed, 57 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 264594947c3b..1380ed313476 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -7,6 +7,7 @@
#include "tdp_mmu.h"
#include "spte.h"
+#include <asm/cmpxchg.h>
#include <trace/events/kvm.h>
#ifdef CONFIG_X86_64
@@ -226,7 +227,8 @@ static void tdp_mmu_free_sp_rcu_callback(struct rcu_head
*head)
}
static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
- u64 old_spte, u64 new_spte, int level);
+ u64 old_spte, u64 new_spte, int level,
+ bool atomic);
static int kvm_mmu_page_as_id(struct kvm_mmu_page *sp)
{
@@ -320,15 +322,19 @@ static void tdp_mmu_unlink_page(struct kvm *kvm, struct
kvm_mmu_page *sp,
*
* @kvm: kvm instance
* @pt: the page removed from the paging structure
+ * @atomic: Use atomic operations to clear the SPTEs in any disconnected
+ * pages of memory.
*
* Given a page table that has been removed from the TDP paging structure,
* iterates through the page table to clear SPTEs and free child page tables.
*/
-static void handle_disconnected_tdp_mmu_page(struct kvm *kvm, u64 *pt)
+static void handle_disconnected_tdp_mmu_page(struct kvm *kvm, u64 *pt,
+ bool atomic)
{
struct kvm_mmu_page *sp;
gfn_t gfn;
int level;
+ u64 *sptep;
u64 old_child_spte;
int i;
@@ -341,11 +347,17 @@ static void handle_disconnected_tdp_mmu_page(struct kvm
*kvm, u64 *pt)
tdp_mmu_unlink_page(kvm, sp, atomic);
for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
- old_child_spte = READ_ONCE(*(pt + i));
- WRITE_ONCE(*(pt + i), 0);
+ sptep = pt + i;
+
+ if (atomic) {
+ old_child_spte = xchg(sptep, 0);
+ } else {
+ old_child_spte = READ_ONCE(*sptep);
+ WRITE_ONCE(*sptep, 0);
+ }
handle_changed_spte(kvm, kvm_mmu_page_as_id(sp),
gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)),
- old_child_spte, 0, level - 1);
+ old_child_spte, 0, level - 1, atomic);
}
kvm_flush_remote_tlbs_with_address(kvm, gfn,
@@ -362,12 +374,15 @@ static void handle_disconnected_tdp_mmu_page(struct kvm
*kvm, u64 *pt)
* @old_spte: The value of the SPTE before the change
* @new_spte: The value of the SPTE after the change
* @level: the level of the PT the SPTE is part of in the paging structure
+ * @atomic: Use atomic operations to clear the SPTEs in any disconnected
+ * pages of memory.
*
* Handle bookkeeping that might result from the modification of a SPTE.
* This function must be called for all TDP SPTE modifications.
*/
static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
- u64 old_spte, u64 new_spte, int level)
+ u64 old_spte, u64 new_spte, int level,
+ bool atomic)
{
bool was_present = is_shadow_present_pte(old_spte);
bool is_present = is_shadow_present_pte(new_spte);
@@ -439,18 +454,50 @@ static void __handle_changed_spte(struct kvm *kvm, int
as_id, gfn_t gfn,
*/
if (was_present && !was_leaf && (pfn_changed || !is_present))
handle_disconnected_tdp_mmu_page(kvm,
- spte_to_child_pt(old_spte, level));
+ spte_to_child_pt(old_spte, level), atomic);
}
static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
- u64 old_spte, u64 new_spte, int level)
+ u64 old_spte, u64 new_spte, int level,
+ bool atomic)
{
- __handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level);
+ __handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level,
+ atomic);
handle_changed_spte_acc_track(old_spte, new_spte, level);
handle_changed_spte_dirty_log(kvm, as_id, gfn, old_spte,
new_spte, level);
}
+/*
+ * tdp_mmu_set_spte_atomic - Set a TDP MMU SPTE atomically and handle the
+ * associated bookkeeping
+ *
+ * @kvm: kvm instance
+ * @iter: a tdp_iter instance currently on the SPTE that should be set
+ * @new_spte: The value the SPTE should be set to
+ * Returns: true if the SPTE was set, false if it was not. If false is
returned,
+ * this function will have no side-effects.
+ */
+static inline bool tdp_mmu_set_spte_atomic(struct kvm *kvm,
+ struct tdp_iter *iter,
+ u64 new_spte)
+{
+ u64 *root_pt = tdp_iter_root_pt(iter);
+ struct kvm_mmu_page *root = sptep_to_sp(root_pt);
+ int as_id = kvm_mmu_page_as_id(root);
+
+ kvm_mmu_lock_assert_held_shared(kvm);
+
+ if (cmpxchg64(iter->sptep, iter->old_spte, new_spte) != iter->old_spte)
+ return false;
+
+ handle_changed_spte(kvm, as_id, iter->gfn, iter->old_spte, new_spte,
+ iter->level, true);
+
+ return true;
+}
+
+
/*
* __tdp_mmu_set_spte - Set a TDP MMU SPTE and handle the associated
bookkeeping
* @kvm: kvm instance
@@ -480,7 +527,7 @@ static inline void __tdp_mmu_set_spte(struct kvm *kvm,
struct tdp_iter *iter,
WRITE_ONCE(*iter->sptep, new_spte);
__handle_changed_spte(kvm, as_id, iter->gfn, iter->old_spte, new_spte,
- iter->level);
+ iter->level, false);
if (record_acc_track)
handle_changed_spte_acc_track(iter->old_spte, new_spte,
iter->level);
--
2.30.0.284.gd98b1dd5eaa7-goog
