linux-kernel - [PATCH v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level

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Date:   Sun,  8 Aug 2021 14:26:56 -0500
From:   Wei Huang <wei.huang2@....com>
To:     kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, pbonzini@...hat.com,
        seanjc@...gle.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com
Subject: [PATCH v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level

AMD future CPUs will require a 5-level NPT if host CR4.LA57 is set.
To prevent kvm_mmu_get_tdp_level() from incorrectly changing NPT level
on behalf of CPUs, add a new parameter in kvm_configure_mmu() to force
a fixed TDP level.

Signed-off-by: Wei Huang <wei.huang2@....com>
---
 arch/x86/include/asm/kvm_host.h |  5 ++---
 arch/x86/kvm/mmu/mmu.c          | 10 ++++++++--
 arch/x86/kvm/svm/svm.c          |  4 +++-
 arch/x86/kvm/vmx/vmx.c          |  3 ++-
 4 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 974cbfb1eefe..6d16f75cc8da 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -723,7 +723,6 @@ struct kvm_vcpu_arch {
 
 	u64 reserved_gpa_bits;
 	int maxphyaddr;
-	int max_tdp_level;
 
 	/* emulate context */
 
@@ -1747,8 +1746,8 @@ void kvm_mmu_invalidate_gva(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid);
 void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd);
 
-void kvm_configure_mmu(bool enable_tdp, int tdp_max_root_level,
-		       int tdp_huge_page_level);
+void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
+		       int tdp_max_root_level, int tdp_huge_page_level);
 
 static inline u16 kvm_read_ldt(void)
 {
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 66f7f5bc3482..c11ee4531f6d 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -97,6 +97,7 @@ module_param_named(flush_on_reuse, force_flush_and_sync_on_reuse, bool, 0644);
 bool tdp_enabled = false;
 
 static int max_huge_page_level __read_mostly;
+static int tdp_root_level __read_mostly;
 static int max_tdp_level __read_mostly;
 
 enum {
@@ -4562,6 +4563,10 @@ static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,
 
 static inline int kvm_mmu_get_tdp_level(struct kvm_vcpu *vcpu)
 {
+	/* tdp_root_level is architecture forced level, use it if nonzero */
+	if (tdp_root_level)
+		return tdp_root_level;
+
 	/* Use 5-level TDP if and only if it's useful/necessary. */
 	if (max_tdp_level == 5 && cpuid_maxphyaddr(vcpu) <= 48)
 		return 4;
@@ -5253,10 +5258,11 @@ void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid)
 	 */
 }
 
-void kvm_configure_mmu(bool enable_tdp, int tdp_max_root_level,
-		       int tdp_huge_page_level)
+void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
+		       int tdp_max_root_level, int tdp_huge_page_level)
 {
 	tdp_enabled = enable_tdp;
+	tdp_root_level = tdp_forced_root_level;
 	max_tdp_level = tdp_max_root_level;
 
 	/*
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e8ccab50ebf6..f361d466e18e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1015,7 +1015,9 @@ static __init int svm_hardware_setup(void)
 	if (!boot_cpu_has(X86_FEATURE_NPT))
 		npt_enabled = false;
 
-	kvm_configure_mmu(npt_enabled, get_max_npt_level(), PG_LEVEL_1G);
+	/* Force VM NPT level equal to the host's max NPT level */
+	kvm_configure_mmu(npt_enabled, get_max_npt_level(),
+			  get_max_npt_level(), PG_LEVEL_1G);
 	pr_info("kvm: Nested Paging %sabled\n", npt_enabled ? "en" : "dis");
 
 	/* Note, SEV setup consumes npt_enabled. */
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 927a552393b9..034e1397c7d5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7803,7 +7803,8 @@ static __init int hardware_setup(void)
 		ept_lpage_level = PG_LEVEL_2M;
 	else
 		ept_lpage_level = PG_LEVEL_4K;
-	kvm_configure_mmu(enable_ept, vmx_get_max_tdp_level(), ept_lpage_level);
+	kvm_configure_mmu(enable_ept, 0, vmx_get_max_tdp_level(),
+			  ept_lpage_level);
 
 	/*
 	 * Only enable PML when hardware supports PML feature, and both EPT
-- 
2.31.1