linux-kernel - [PATCH v7 03/18] KVM: x86/mmu: Factor out spte atomic bit clearing routine

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Message-ID: <20240926013506.860253-4-jthoughton@google.com>
Date: Thu, 26 Sep 2024 01:34:51 +0000
From: James Houghton <jthoughton@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, David Matlack <dmatlack@...gle.com>, 
	David Rientjes <rientjes@...gle.com>, James Houghton <jthoughton@...gle.com>, 
	Jason Gunthorpe <jgg@...pe.ca>, Jonathan Corbet <corbet@....net>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Wei Xu <weixugc@...gle.com>, Yu Zhao <yuzhao@...gle.com>, 
	Axel Rasmussen <axelrasmussen@...gle.com>, kvm@...r.kernel.org, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v7 03/18] KVM: x86/mmu: Factor out spte atomic bit clearing routine

This new function, tdp_mmu_clear_spte_bits_atomic(), will be used in a
follow-up patch to enable lockless Accessed and R/W/X bit clearing.

Signed-off-by: James Houghton <jthoughton@...gle.com>
---
 arch/x86/kvm/mmu/tdp_iter.h | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h
index 2880fd392e0c..ec171568487c 100644
--- a/arch/x86/kvm/mmu/tdp_iter.h
+++ b/arch/x86/kvm/mmu/tdp_iter.h
@@ -25,6 +25,13 @@ static inline u64 kvm_tdp_mmu_write_spte_atomic(tdp_ptep_t sptep, u64 new_spte)
 	return xchg(rcu_dereference(sptep), new_spte);
 }
 
+static inline u64 tdp_mmu_clear_spte_bits_atomic(tdp_ptep_t sptep, u64 mask)
+{
+	atomic64_t *sptep_atomic = (atomic64_t *)rcu_dereference(sptep);
+
+	return (u64)atomic64_fetch_and(~mask, sptep_atomic);
+}
+
 static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte)
 {
 	KVM_MMU_WARN_ON(is_ept_ve_possible(new_spte));
@@ -65,10 +72,8 @@ static inline u64 tdp_mmu_clear_spte_bits(tdp_ptep_t sptep, u64 old_spte,
 {
 	atomic64_t *sptep_atomic;
 
-	if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level)) {
-		sptep_atomic = (atomic64_t *)rcu_dereference(sptep);
-		return (u64)atomic64_fetch_and(~mask, sptep_atomic);
-	}
+	if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level))
+		return tdp_mmu_clear_spte_bits_atomic(sptep, mask);
 
 	__kvm_tdp_mmu_write_spte(sptep, old_spte & ~mask);
 	return old_spte;
-- 
2.46.0.792.g87dc391469-goog