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Message-ID: <41c87e38-4855-48da-bb7e-fd9b3c39a439@linux.intel.com>
Date: Thu, 4 Sep 2025 17:23:13 +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 v10 02/21] KVM: selftests: Expose functions to get default
sregs values
On 9/4/2025 2:54 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>
Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>
One suggestion:
It's better to add change history so that reviewers can know the change quickly
without comparing b/t versions.
> ---
> .../selftests/kvm/include/x86/processor.h | 33 +++++++++++++++++++
> .../testing/selftests/kvm/lib/x86/processor.c | 12 +++----
> 2 files changed, 38 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..f610c09cadf4 100644
> --- a/tools/testing/selftests/kvm/include/x86/processor.h
> +++ b/tools/testing/selftests/kvm/include/x86/processor.h
> @@ -27,6 +27,10 @@ extern uint64_t 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. */
> @@ -1456,4 +1460,33 @@ void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
>
> bool sys_clocksource_is_based_on_tsc(void);
>
> +static inline uint16_t kvm_get_default_idt_limit(void)
> +{
> + return NUM_INTERRUPTS * sizeof(struct idt_entry) - 1;
> +}
> +
> +static inline uint16_t kvm_get_default_gdt_limit(void)
> +{
> + return getpagesize() - 1;
> +}
> +
> +static inline uint64_t kvm_get_default_cr0(void)
> +{
> + return X86_CR0_PE | X86_CR0_NE | X86_CR0_PG;
> +}
> +
> +static inline 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;
> +}
> +
> +static inline uint64_t 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 d4c19ac885a9..83efcf48faad 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -498,15 +498,13 @@ 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);
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