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@google.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);