Merge branch 'v6.0-rc7'

Merge upstream to get RAPTORLAKE_S

Signed-off-by: Peter Zijlstra <peterz@infradead.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index f3744eea45f5..7670c13ce251 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -343,7 +343,7 @@ static __always_inline bool is_rsvd_spte(struct rsvd_bits_validate *rsvd_check,
 }
 
 /*
- * An shadow-present leaf SPTE may be non-writable for 3 possible reasons:
+ * A shadow-present leaf SPTE may be non-writable for 4 possible reasons:
  *
  *  1. To intercept writes for dirty logging. KVM write-protects huge pages
  *     so that they can be split be split down into the dirty logging
@@ -361,8 +361,13 @@ static __always_inline bool is_rsvd_spte(struct rsvd_bits_validate *rsvd_check,
  *     read-only memslot or guest memory backed by a read-only VMA. Writes to
  *     such pages are disallowed entirely.
  *
- * To keep track of why a given SPTE is write-protected, KVM uses 2
- * software-only bits in the SPTE:
+ *  4. To emulate the Accessed bit for SPTEs without A/D bits.  Note, in this
+ *     case, the SPTE is access-protected, not just write-protected!
+ *
+ * For cases #1 and #4, KVM can safely make such SPTEs writable without taking
+ * mmu_lock as capturing the Accessed/Dirty state doesn't require taking it.
+ * To differentiate #1 and #4 from #2 and #3, KVM uses two software-only bits
+ * in the SPTE:
  *
  *  shadow_mmu_writable_mask, aka MMU-writable -
  *    Cleared on SPTEs that KVM is currently write-protecting for shadow paging
@@ -391,7 +396,8 @@ static __always_inline bool is_rsvd_spte(struct rsvd_bits_validate *rsvd_check,
  * shadow page tables between vCPUs. Write-protecting an SPTE for dirty logging
  * (which does not clear the MMU-writable bit), does not flush TLBs before
  * dropping the lock, as it only needs to synchronize guest writes with the
- * dirty bitmap.
+ * dirty bitmap. Similarly, making the SPTE inaccessible (and non-writable) for
+ * access-tracking via the clear_young() MMU notifier also does not flush TLBs.
  *
  * So, there is the problem: clearing the MMU-writable bit can encounter a
  * write-protected SPTE while CPUs still have writable mappings for that SPTE