linux-kernel - [PATCH 16/22] KVM: x86/mmu: remove redundant bits from extended role

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Date:   Thu, 14 Apr 2022 03:39:54 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     seanjc@...gle.com
Subject: [PATCH 16/22] KVM: x86/mmu: remove redundant bits from extended role

Before the separation of the CPU and the MMU role, CR0.PG was not
available in the base MMU role, because two-dimensional paging always
used direct=1 in the MMU role.  However, now that the raw role is
snapshotted in mmu->cpu_role, CR0.PG *can* be found (though inverted)
as !cpu_role.base.direct.  There is no need to store it again in union
kvm_mmu_extended_role; instead, write an is_cr0_pg accessor by hand that
takes care of the inversion.

Likewise, CR4.PAE is now always present in the CPU role as
!cpu_role.base.has_4_byte_gpte.  The inversion makes certain tests on
the MMU role easier, and is easily hidden by the is_cr4_pae accessor
when operating on the CPU role.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/include/asm/kvm_host.h |  2 --
 arch/x86/kvm/mmu/mmu.c          | 14 ++++++++++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6bc5550ae530..52ceeadbed28 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -367,8 +367,6 @@ union kvm_mmu_extended_role {
 	struct {
 		unsigned int valid:1;
 		unsigned int execonly:1;
-		unsigned int cr0_pg:1;
-		unsigned int cr4_pae:1;
 		unsigned int cr4_pse:1;
 		unsigned int cr4_pke:1;
 		unsigned int cr4_smap:1;
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 483a3761db81..cf8a41675a79 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -224,16 +224,24 @@ static inline bool __maybe_unused is_##reg##_##name(struct kvm_mmu *mmu)	\
 {								\
 	return !!(mmu->cpu_role. base_or_ext . reg##_##name);	\
 }
-BUILD_MMU_ROLE_ACCESSOR(ext,  cr0, pg);
 BUILD_MMU_ROLE_ACCESSOR(base, cr0, wp);
 BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pse);
-BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pae);
 BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, smep);
 BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, smap);
 BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pke);
 BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, la57);
 BUILD_MMU_ROLE_ACCESSOR(base, efer, nx);
 
+static inline bool is_cr0_pg(struct kvm_mmu *mmu)
+{
+        return !mmu->cpu_role.base.direct;
+}
+
+static inline bool is_cr4_pae(struct kvm_mmu *mmu)
+{
+        return !mmu->cpu_role.base.has_4_byte_gpte;
+}
+
 static struct kvm_mmu_role_regs vcpu_to_role_regs(struct kvm_vcpu *vcpu)
 {
 	struct kvm_mmu_role_regs regs = {
@@ -4712,8 +4720,6 @@ kvm_calc_cpu_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs)
 	else
 		role.base.level = PT32_ROOT_LEVEL;
 
-	role.ext.cr0_pg = 1;
-	role.ext.cr4_pae = ____is_cr4_pae(regs);
 	role.ext.cr4_smep = ____is_cr4_smep(regs);
 	role.ext.cr4_smap = ____is_cr4_smap(regs);
 	role.ext.cr4_pse = ____is_cr4_pse(regs);
-- 
2.31.1