linux-kernel - [PATCH 06/16] KVM: x86/mmu: Refactor the per-slot level calculation in mapping

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Message-Id: <20191206235729.29263-7-sean.j.christopherson@intel.com>
Date:   Fri,  6 Dec 2019 15:57:19 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Cc:     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>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 06/16] KVM: x86/mmu: Refactor the per-slot level calculation in mapping_level()

Invert the loop which adjusts the allowed page level based on what's
compatible with the associated memslot to use a largest-to-smallest
page size walk.  This paves the way for passing around a "max level"
variable instead of having redundant checks and/or multiple booleans.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/mmu/mmu.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index e4a96236aa14..bd1711201181 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1326,7 +1326,7 @@ gfn_to_memslot_dirty_bitmap(struct kvm_vcpu *vcpu, gfn_t gfn,
 static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn,
 			 bool *force_pt_level)
 {
-	int host_level, level, max_level;
+	int host_level, max_level;
 	struct kvm_memory_slot *slot;
 
 	if (unlikely(*force_pt_level))
@@ -1343,12 +1343,12 @@ static int mapping_level(struct kvm_vcpu *vcpu, gfn_t large_gfn,
 		return host_level;
 
 	max_level = min(kvm_x86_ops->get_lpage_level(), host_level);
-
-	for (level = PT_DIRECTORY_LEVEL; level <= max_level; ++level)
-		if (__mmu_gfn_lpage_is_disallowed(large_gfn, level, slot))
+	for ( ; max_level > PT_PAGE_TABLE_LEVEL; max_level--) {
+		if (!__mmu_gfn_lpage_is_disallowed(large_gfn, max_level, slot))
 			break;
+	}
 
-	return level - 1;
+	return max_level;
 }
 
 /*
-- 
2.24.0