linux-kernel - [PATCH 12/23] KVM: MMU: remove ept

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Message-Id: <20220204115718.14934-13-pbonzini@redhat.com>
Date:   Fri,  4 Feb 2022 06:57:07 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     dmatlack@...gle.com, seanjc@...gle.com, vkuznets@...hat.com
Subject: [PATCH 12/23] KVM: MMU: remove ept_ad field

The similar field in the CPU role, ad_disabled, is initialized to the
opposite value for shadow EPT, and left zero for "normal" EPT because
guest page tables always have A/D bits.  So, read it from the CPU role,
like other page-format fields; it just has to be inverted to account
for the different polarity.

In the MMU role, instead, the ad_disabled bit is set according to
shadow_accessed_mask, so it would have been incorrect to replace
PT_HAVE_ACCESSED_DIRTY with just !mmu->mmu_role.base.ad_disabled.
However, with the separation of CPU and MMU roles, we might even get
rid of the PT_HAVE_ACCESSED_DIRTY macro altogether.  I am not doing this
because the macro has a small effect in terms of dead code elimination:

   text	   data	    bss	    dec	    hex
 103544	  16665	    112	 120321	  1d601    # as of this patch
 103746	  16665	    112	 120523	  1d6cb    # without PT_HAVE_ACCESSED_DIRTY

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/include/asm/kvm_host.h | 1 -
 arch/x86/kvm/mmu/mmu.c          | 1 -
 arch/x86/kvm/mmu/paging_tmpl.h  | 2 +-
 3 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 427ee486309c..795b345361c8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -436,7 +436,6 @@ struct kvm_mmu {
 	union kvm_mmu_role mmu_role;
 	u8 root_level;
 	u8 shadow_root_level;
-	u8 ept_ad;
 	bool direct_map;
 	struct kvm_mmu_root_info prev_roots[KVM_MMU_NUM_PREV_ROOTS];
 
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 74789295f922..d6b5d8c1c0dc 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4915,7 +4915,6 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
 
 		context->shadow_root_level = level;
 
-		context->ept_ad = accessed_dirty;
 		context->page_fault = ept_page_fault;
 		context->gva_to_gpa = ept_gva_to_gpa;
 		context->sync_page = ept_sync_page;
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index b9f472f27077..1b5c7d03f94b 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -64,7 +64,7 @@
 	#define PT_LEVEL_BITS PT64_LEVEL_BITS
 	#define PT_GUEST_DIRTY_SHIFT 9
 	#define PT_GUEST_ACCESSED_SHIFT 8
-	#define PT_HAVE_ACCESSED_DIRTY(mmu) ((mmu)->ept_ad)
+	#define PT_HAVE_ACCESSED_DIRTY(mmu) (!(mmu)->cpu_role.base.ad_disabled)
 	#define CMPXCHG cmpxchg64
 	#define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL
 #else
-- 
2.31.1