Re: [PATCH v14 09/22] KVM: selftests: Expose functions to get default sregs values

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 7/23/2026 7:13 AM, Lisa Wang wrote:
> From: Sagi Shahar <sagis@google.com>
> 
> 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.
> 
> Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
> Signed-off-by: Sagi Shahar <sagis@google.com>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Lisa Wang <wyihan@google.com>

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>

> ---
>   .../testing/selftests/kvm/include/x86/processor.h  | 35 ++++++++++++++++++++++
>   tools/testing/selftests/kvm/lib/x86/processor.c    | 20 ++++---------
>   2 files changed, 41 insertions(+), 14 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
> index 76180dfaffea..7e00c9414595 100644
> --- a/tools/testing/selftests/kvm/include/x86/processor.h
> +++ b/tools/testing/selftests/kvm/include/x86/processor.h
> @@ -29,6 +29,10 @@ extern u64 guest_tsc_khz;
>   #define MAX_NR_CPUID_ENTRIES 100
>   #endif
>   
> +#ifndef NUM_INTERRUPTS
> +#define NUM_INTERRUPTS 256
> +#endif
> +
>   #define NONCANONICAL 0xaaaaaaaaaaaaaaaaull
>   
>   /* Forced emulation prefix, used to invoke the emulator unconditionally. */
> @@ -1564,4 +1568,35 @@ u64 *tdp_get_pte(struct kvm_vm *vm, u64 l2_gpa);
>   
>   bool sys_clocksource_is_based_on_tsc(void);
>   
> +static inline u16 kvm_get_default_idt_limit(void)
> +{
> +	return NUM_INTERRUPTS * sizeof(struct idt_entry) - 1;
> +}
> +
> +static inline u16 kvm_get_default_gdt_limit(void)
> +{
> +	return getpagesize() - 1;
> +}
> +
> +static inline u64 kvm_get_default_cr0(void)
> +{
> +	return X86_CR0_PE | X86_CR0_NE | X86_CR0_PG;
> +}
> +
> +static inline u64 kvm_get_default_cr4(int pgtable_levels)
> +{
> +	u64 cr4 = X86_CR4_PAE | X86_CR4_OSFXSR;
> +
> +	if (kvm_cpu_has(X86_FEATURE_XSAVE))
> +		cr4 |= X86_CR4_OSXSAVE;
> +	if (pgtable_levels == 5)
> +		cr4 |= X86_CR4_LA57;
> +	return cr4;
> +}
> +
> +static inline u64 kvm_get_default_efer(void)
> +{
> +	return EFER_LME | EFER_LMA | EFER_NX;
> +}
> +
>   #endif /* SELFTEST_KVM_PROCESSOR_H */
> diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
> index 97acc5aaf7b7..ad75e19bb3a2 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -15,10 +15,6 @@
>   #include "tdx/tdx_util.h"
>   #include "vmx.h"
>   
> -#ifndef NUM_INTERRUPTS
> -#define NUM_INTERRUPTS 256
> -#endif
> -
>   gva_t exception_handlers;
>   bool host_cpu_is_amd;
>   bool host_cpu_is_intel;
> @@ -647,17 +643,13 @@ 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.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;
> -	if (vm->mmu.pgtable_levels == 5)
> -		sregs.cr4 |= X86_CR4_LA57;
> -	sregs.efer |= (EFER_LME | EFER_LMA | EFER_NX);
> +	sregs.gdt.limit = kvm_get_default_gdt_limit();
> +
> +	sregs.cr0 = kvm_get_default_cr0();
> +	sregs.cr4 |= kvm_get_default_cr4(vm->mmu.pgtable_levels);
> +	sregs.efer |= kvm_get_default_efer();
>   
>   	kvm_seg_set_unusable(&sregs.ldt);
>   	kvm_seg_set_kernel_code_64bit(&sregs.cs);
>