linux-kernel - [PATCH v6 22/22] KVM: x86/mmu: Consolidate open coded variants of memslot TLB flushes

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Date:   Tue, 18 Feb 2020 13:07:36 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        Christoffer Dall <christoffer.dall@....com>,
        Peter Xu <peterx@...hat.com>,
        Philippe Mathieu-Daudé <f4bug@...at.org>
Subject: [PATCH v6 22/22] KVM: x86/mmu: Consolidate open coded variants of memslot TLB flushes

Replace open coded instances of kvm_arch_flush_remote_tlbs_memslot()'s
functionality with calls to the aforementioned function.  Update the
comment in kvm_arch_flush_remote_tlbs_memslot() to elaborate on how it
is used and why it asserts that slots_lock is held.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/mmu/mmu.c | 34 +++++++++-------------------------
 1 file changed, 9 insertions(+), 25 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 8a6516ce2983..1eb8654cc9d0 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5870,13 +5870,6 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
 				      false);
 	spin_unlock(&kvm->mmu_lock);
 
-	/*
-	 * kvm_mmu_slot_remove_write_access() and kvm_vm_ioctl_get_dirty_log()
-	 * which do tlb flush out of mmu-lock should be serialized by
-	 * kvm->slots_lock otherwise tlb flush would be missed.
-	 */
-	lockdep_assert_held(&kvm->slots_lock);
-
 	/*
 	 * We can flush all the TLBs out of the mmu lock without TLB
 	 * corruption since we just change the spte from writable to
@@ -5889,8 +5882,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
 	 * on PT_WRITABLE_MASK anymore.
 	 */
 	if (flush)
-		kvm_flush_remote_tlbs_with_address(kvm, memslot->base_gfn,
-			memslot->npages);
+		kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);
 }
 
 static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
@@ -5946,8 +5938,11 @@ void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
 					struct kvm_memory_slot *memslot)
 {
 	/*
-	 * All the TLBs can be flushed out of mmu lock, see the comments in
-	 * kvm_mmu_slot_remove_write_access().
+	 * All current use cases for flushing the TLBs for a specific memslot
+	 * are related to dirty logging, and do the TLB flush out of mmu_lock.
+	 * The interaction between the various operations on memslot must be
+	 * serialized by slots_locks to ensure the TLB flush from one operation
+	 * is observed by any other operation on the same memslot.
 	 */
 	lockdep_assert_held(&kvm->slots_lock);
 	kvm_flush_remote_tlbs_with_address(kvm, memslot->base_gfn,
@@ -5963,8 +5958,6 @@ void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
 	flush = slot_handle_leaf(kvm, memslot, __rmap_clear_dirty, false);
 	spin_unlock(&kvm->mmu_lock);
 
-	lockdep_assert_held(&kvm->slots_lock);
-
 	/*
 	 * It's also safe to flush TLBs out of mmu lock here as currently this
 	 * function is only used for dirty logging, in which case flushing TLB
@@ -5972,8 +5965,7 @@ void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
 	 * dirty_bitmap.
 	 */
 	if (flush)
-		kvm_flush_remote_tlbs_with_address(kvm, memslot->base_gfn,
-				memslot->npages);
+		kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_slot_leaf_clear_dirty);
 
@@ -5987,12 +5979,8 @@ void kvm_mmu_slot_largepage_remove_write_access(struct kvm *kvm,
 					false);
 	spin_unlock(&kvm->mmu_lock);
 
-	/* see kvm_mmu_slot_remove_write_access */
-	lockdep_assert_held(&kvm->slots_lock);
-
 	if (flush)
-		kvm_flush_remote_tlbs_with_address(kvm, memslot->base_gfn,
-				memslot->npages);
+		kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_slot_largepage_remove_write_access);
 
@@ -6005,12 +5993,8 @@ void kvm_mmu_slot_set_dirty(struct kvm *kvm,
 	flush = slot_handle_all_level(kvm, memslot, __rmap_set_dirty, false);
 	spin_unlock(&kvm->mmu_lock);
 
-	lockdep_assert_held(&kvm->slots_lock);
-
-	/* see kvm_mmu_slot_leaf_clear_dirty */
 	if (flush)
-		kvm_flush_remote_tlbs_with_address(kvm, memslot->base_gfn,
-				memslot->npages);
+		kvm_arch_flush_remote_tlbs_memslot(kvm, memslot);
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_slot_set_dirty);
 
-- 
2.24.1