linux-kernel - [PATCH v9 03/19] KVM: selftests: Expose functions to get default sregs values

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Message-ID: <20250821042915.3712925-4-sagis@google.com>
Date: Wed, 20 Aug 2025 21:28:56 -0700
From: Sagi Shahar <sagis@...gle.com>
To: linux-kselftest@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>, 
	Shuah Khan <shuah@...nel.org>, Sean Christopherson <seanjc@...gle.com>, 
	Ackerley Tng <ackerleytng@...gle.com>, Ryan Afranji <afranji@...gle.com>, 
	Andrew Jones <ajones@...tanamicro.com>, Isaku Yamahata <isaku.yamahata@...el.com>, 
	Erdem Aktas <erdemaktas@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Sagi Shahar <sagis@...gle.com>, Roger Wang <runanwang@...gle.com>, 
	Binbin Wu <binbin.wu@...ux.intel.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	"Pratik R. Sampat" <pratikrajesh.sampat@....com>, Reinette Chatre <reinette.chatre@...el.com>, 
	Ira Weiny <ira.weiny@...el.com>, Chao Gao <chao.gao@...el.com>, 
	Chenyi Qiang <chenyi.qiang@...el.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v9 03/19] KVM: selftests: Expose functions to get default
 sregs values

TDX can't set sregs values directly using KVM_SET_SREGS. Expose the
default values of certain sregs used by TDX VMs so they can be set
manually.

Signed-off-by: Sagi Shahar <sagis@...gle.com>
---
 .../selftests/kvm/include/x86/processor.h     |  6 +++
 .../testing/selftests/kvm/lib/x86/processor.c | 41 +++++++++++++++----
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
index 2efb05c2f2fb..5c16507f9b2d 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -1026,6 +1026,12 @@ static inline struct kvm_cpuid2 *allocate_kvm_cpuid2(int nr_entries)
 
 void vcpu_init_cpuid(struct kvm_vcpu *vcpu, const struct kvm_cpuid2 *cpuid);
 
+uint16_t kvm_get_default_idt_limit(void);
+uint16_t kvm_get_default_gdt_limit(void);
+uint64_t kvm_get_default_cr0(void);
+uint64_t kvm_get_default_cr4(void);
+uint64_t kvm_get_default_efer(void);
+
 static inline void vcpu_get_cpuid(struct kvm_vcpu *vcpu)
 {
 	vcpu_ioctl(vcpu, KVM_GET_CPUID2, vcpu->cpuid);
diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
index d4c19ac885a9..b2a4b11ac8c0 100644
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -488,6 +488,35 @@ static void kvm_seg_set_tss_64bit(vm_vaddr_t base, struct kvm_segment *segp)
 	segp->present = 1;
 }
 
+uint16_t kvm_get_default_idt_limit(void)
+{
+	return NUM_INTERRUPTS * sizeof(struct idt_entry) - 1;
+}
+
+uint16_t kvm_get_default_gdt_limit(void)
+{
+	return getpagesize() - 1;
+}
+
+uint64_t kvm_get_default_cr0(void)
+{
+	return X86_CR0_PE | X86_CR0_NE | X86_CR0_PG;
+}
+
+uint64_t kvm_get_default_cr4(void)
+{
+	uint64_t cr4 = X86_CR4_PAE | X86_CR4_OSFXSR;
+
+	if (kvm_cpu_has(X86_FEATURE_XSAVE))
+		cr4 |= X86_CR4_OSXSAVE;
+	return cr4;
+}
+
+uint64_t kvm_get_default_efer(void)
+{
+	return EFER_LME | EFER_LMA | EFER_NX;
+}
+
 static void vcpu_init_sregs(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
 {
 	struct kvm_sregs sregs;
@@ -498,15 +527,13 @@ static void vcpu_init_sregs(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
 	vcpu_sregs_get(vcpu, &sregs);
 
 	sregs.idt.base = vm->arch.idt;
-	sregs.idt.limit = NUM_INTERRUPTS * sizeof(struct idt_entry) - 1;
+	sregs.idt.limit = kvm_get_default_idt_limit();
 	sregs.gdt.base = vm->arch.gdt;
-	sregs.gdt.limit = getpagesize() - 1;
+	sregs.gdt.limit = kvm_get_default_gdt_limit();
 
-	sregs.cr0 = X86_CR0_PE | X86_CR0_NE | X86_CR0_PG;
-	sregs.cr4 |= X86_CR4_PAE | X86_CR4_OSFXSR;
-	if (kvm_cpu_has(X86_FEATURE_XSAVE))
-		sregs.cr4 |= X86_CR4_OSXSAVE;
-	sregs.efer |= (EFER_LME | EFER_LMA | EFER_NX);
+	sregs.cr0 = kvm_get_default_cr0();
+	sregs.cr4 |= kvm_get_default_cr4();
+	sregs.efer |= kvm_get_default_efer();
 
 	kvm_seg_set_unusable(&sregs.ldt);
 	kvm_seg_set_kernel_code_64bit(&sregs.cs);
-- 
2.51.0.rc1.193.gad69d77794-goog