[PATCH 22/27] KVM: x86/mmu: Assert that correct locks are held for page write-tracking

Sean Christopherson
2022-12-23T01:00:44Z

When adding/removing gfns to/from write-tracking, assert that mmu_lock
is held for write, and that either slots_lock or kvm->srcu is held.
mmu_lock must be held for write to protect gfn_write_track's refcount,
and SRCU or slots_lock must be held to protect the memslot itself.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/mmu/page_track.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index 1eb516119fdb..209f6beba5ac 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -11,6 +11,7 @@
* Xiao Guangrong <guangrong.xiao@linux.intel.com>
*/

+#include <linux/lockdep.h>
#include <linux/kvm_host.h>
#include <linux/rculist.h>

@@ -76,9 +77,6 @@ static void update_gfn_write_track(struct kvm_memory_slot *slot, gfn_t gfn,
* add guest page to the tracking pool so that corresponding access on that
* page will be intercepted.
*
- * It should be called under the protection both of mmu-lock and kvm->srcu
- * or kvm->slots_lock.
- *
* @kvm: the guest instance we are interested in.
* @slot: the @gfn belongs to.
* @gfn: the guest page.
@@ -86,6 +84,11 @@ static void update_gfn_write_track(struct kvm_memory_slot *slot, gfn_t gfn,
void kvm_write_track_add_gfn(struct kvm *kvm, struct kvm_memory_slot *slot,
gfn_t gfn)
{
+ lockdep_assert_held_write(&kvm->mmu_lock);
+
+ lockdep_assert_once(lockdep_is_held(&kvm->slots_lock) ||
+ srcu_read_lock_held(&kvm->srcu));
+
if (WARN_ON(!kvm_page_track_write_tracking_enabled(kvm)))
return;

@@ -106,9 +109,6 @@ EXPORT_SYMBOL_GPL(kvm_write_track_add_gfn);
* remove the guest page from the tracking pool which stops the interception
* of corresponding access on that page.
*
- * It should be called under the protection both of mmu-lock and kvm->srcu
- * or kvm->slots_lock.
- *
* @kvm: the guest instance we are interested in.
* @slot: the @gfn belongs to.
* @gfn: the guest page.
@@ -116,6 +116,11 @@ EXPORT_SYMBOL_GPL(kvm_write_track_add_gfn);
void kvm_write_track_remove_gfn(struct kvm *kvm,
struct kvm_memory_slot *slot, gfn_t gfn)
{
+ lockdep_assert_held_write(&kvm->mmu_lock);
+
+ lockdep_assert_once(lockdep_is_held(&kvm->slots_lock) ||
+ srcu_read_lock_held(&kvm->srcu));
+
if (WARN_ON(!kvm_page_track_write_tracking_enabled(kvm)))
return;

--
2.39.0.314.g84b9a713c41-goog