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

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Message-ID: <e04d31a3-3243-4141-88d2-1f0ade6d648a@linux.intel.com>
Date: Tue, 26 Aug 2025 10:36:36 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Sagi Shahar <sagis@...gle.com>
Cc: 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>,
 Roger Wang <runanwang@...gle.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>, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org
Subject: Re: [PATCH v9 03/19] KVM: selftests: Expose functions to get default
 sregs values



On 8/21/2025 12:28 PM, Sagi Shahar wrote:
> 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);
Can these be defined in the header file as static inline?

> +
>   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);