linux-kernel - [PATCH 2/3] KVM: x86/mmu: Relocate kvm_mmu_page.tdp_mmu

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Message-Id: <20210901221023.1303578-3-seanjc@google.com>
Date:   Wed,  1 Sep 2021 15:10:22 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.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, Jia He <justin.he@....com>
Subject: [PATCH 2/3] KVM: x86/mmu: Relocate kvm_mmu_page.tdp_mmu_page for
 better cache locality

Move "tdp_mmu_page" into the 1-byte void left by the recently removed
"mmio_cached" so that it resides in the first 64 bytes of kvm_mmu_page,
i.e. in the same cache line as the most commonly accessed fields.

Don't bother wrapping tdp_mmu_page in CONFIG_X86_64, including the field in
32-bit builds doesn't affect the size of kvm_mmu_page, and a future patch
can always wrap the field in the unlikely event KVM gains a 1-byte flag
that is 32-bit specific.

Note, the size of kvm_mmu_page is also unchanged on CONFIG_X86_64=y due
to it previously sharing an 8-byte chunk with write_flooding_count.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu_internal.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 9bfa46b35201..4b06e6040e90 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -35,6 +35,7 @@ struct kvm_mmu_page {
 	struct hlist_node hash_link;
 	struct list_head lpage_disallowed_link;
 
+	bool tdp_mmu_page;
 	bool unsync;
 	u8 mmu_valid_gen;
 	bool lpage_disallowed; /* Can't be replaced by an equiv large page */
@@ -70,8 +71,6 @@ struct kvm_mmu_page {
 	atomic_t write_flooding_count;
 
 #ifdef CONFIG_X86_64
-	bool tdp_mmu_page;
-
 	/* Used for freeing the page asynchronously if it is a TDP MMU page. */
 	struct rcu_head rcu_head;
 #endif
-- 
2.33.0.153.gba50c8fa24-goog