[PATCH v2 2/7] KVM: arm64: MTE: Update code comments

Aneesh Kumar K.V (Arm)
2025-01-10T11:00:44Z

commit d77e59a8fccd ("arm64: mte: Lock a page for MTE tag
initialisation") updated the locking such the kernel now allows
VM_SHARED mapping with MTE. Update the code comment to reflect this.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
arch/arm64/kvm/mmu.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index c9d46ad57e52..eb8220a409e1 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1391,11 +1391,11 @@ static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva)
* able to see the page's tags and therefore they must be initialised first. If
* PG_mte_tagged is set, tags have already been initialised.
*
- * The race in the test/set of the PG_mte_tagged flag is handled by:
- * - preventing VM_SHARED mappings in a memslot with MTE preventing two VMs
- * racing to santise the same page
- * - mmap_lock protects between a VM faulting a page in and the VMM performing
- * an mprotect() to add VM_MTE
+ * The race in the test/set of the PG_mte_tagged flag is handled by using
+ * PG_mte_lock and PG_mte_tagged together. if PG_mte_lock is found unset, we can
+ * go ahead and clear the page tags. if PG_mte_lock is found set, then the page
+ * tags are already cleared or there is a parallel tag clearing is going on. We
+ * wait for the parallel tag clear to finish by waiting on PG_mte_tagged bit.
*/
static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
unsigned long size)
--
2.43.0