[Intel-gfx] [PATCH v3 24/28] KVM: x86/mmu: Assert that correct locks are held for page write-tracking

Sean Christopherson
2023-05-13T00:36:59Z

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.

Tested-by: Yan Zhao <yan.y.zhao@intel.com>
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 b835ba7f325c..29ae61f1e303 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -12,6 +12,7 @@
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

@@ -77,9 +78,6 @@ 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.
@@ -87,6 +85,11 @@ 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;

@@ -107,9 +110,6 @@ 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.
@@ -117,6 +117,11 @@ 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;

--
2.40.1.606.ga4b1b128d6-goog