From: Paolo Bonzini <pbonzini@redhat.com>
Date: Sun, 12 May 2024 07:18:30 +0000 (-0400)
Subject: Merge tag 'kvm-x86-mmu-6.10' of https://github.com/kvm-x86/linux into HEAD
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=5a1c72e07e830dda424f2929332a1435c9736da3;p=linux.git

Merge tag 'kvm-x86-mmu-6.10' of https://github.com/kvm-x86/linux into HEAD

KVM x86 MMU changes for 6.10:

 - Process TDP MMU SPTEs that are are zapped while holding mmu_lock for read
   after replacing REMOVED_SPTE with '0' and flushing remote TLBs, which allows
   vCPU tasks to repopulate the zapped region while the zapper finishes tearing
   down the old, defunct page tables.

 - Fix a longstanding, likely benign-in-practice race where KVM could fail to
   detect a write from kvm_mmu_track_write() to a shadowed GPTE if the GPTE is
   first page table being shadowed.
---

5a1c72e07e830dda424f2929332a1435c9736da3
diff --cc arch/x86/kvm/mmu/tdp_mmu.c
index b5be7e949bd8c,afd00f79e741b..1259dd63defc8
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@@ -599,12 -614,20 +614,20 @@@ static inline int tdp_mmu_zap_spte_atom
  	/*
  	 * No other thread can overwrite the removed SPTE as they must either
  	 * wait on the MMU lock or use tdp_mmu_set_spte_atomic() which will not
- 	 * overwrite the special removed SPTE value. No bookkeeping is needed
- 	 * here since the SPTE is going from non-present to non-present.  Use
- 	 * the raw write helper to avoid an unnecessary check on volatile bits.
+ 	 * overwrite the special removed SPTE value. Use the raw write helper to
+ 	 * avoid an unnecessary check on volatile bits.
  	 */
 -	__kvm_tdp_mmu_write_spte(iter->sptep, 0);
 +	__kvm_tdp_mmu_write_spte(iter->sptep, SHADOW_NONPRESENT_VALUE);
  
+ 	/*
+ 	 * Process the zapped SPTE after flushing TLBs, and after replacing
+ 	 * REMOVED_SPTE with 0. This minimizes the amount of time vCPUs are
+ 	 * blocked by the REMOVED_SPTE and reduces contention on the child
+ 	 * SPTEs.
+ 	 */
+ 	handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
+ 			    0, iter->level, true);
+ 
  	return 0;
  }