[PATCH] KVM: x86/mmu: Refactor slot null check in kvm_mmu_hugepage_adjust

From: David Matlack <dmatlack@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, Ben Gardon <bgardon@google.com>,
	Joerg Roedel <joro@8bytes.org>, Jim Mattson <jmattson@google.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	David Matlack <dmatlack@google.com>
Subject: [PATCH] KVM: x86/mmu: Refactor slot null check in kvm_mmu_hugepage_adjust
Date: Tue, 24 Aug 2021 23:34:07 +0000	[thread overview]
Message-ID: <20210824233407.1845924-1-dmatlack@google.com> (raw)

The current code is correct but relies on is_error_noslot_pfn() to
ensure slot is not null. The only reason is_error_noslot_pfn() was
checked instead is because we did not have the slot before
commit 6574422f913e ("KVM: x86/mmu: Pass the memslot around via struct
kvm_page_fault") and looking up the memslot is expensive.

Now that the slot is available, explicitly check if it's null and
get rid of the redundant is_error_noslot_pfn() check.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4853c033e6ce..9b5424bcb173 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2925,10 +2925,10 @@ void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
 	if (unlikely(fault->max_level == PG_LEVEL_4K))
 		return;
 
-	if (is_error_noslot_pfn(fault->pfn) || kvm_is_reserved_pfn(fault->pfn))
+	if (!slot || kvm_slot_dirty_track_enabled(slot))
 		return;
 
-	if (kvm_slot_dirty_track_enabled(slot))
+	if (kvm_is_reserved_pfn(fault->pfn))
 		return;
 
 	/*
-- 
2.33.0.rc2.250.ged5fa647cd-goog

