linux-kernel - Re: [PATCH v10 10/21] KVM: selftests: Set up TDX boot parameters region

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Message-ID: <0e8a2035-caeb-4c75-9620-b65df07be1a0@linux.intel.com>
Date: Mon, 8 Sep 2025 16:07:12 +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 10/21] KVM: selftests: Set up TDX boot parameters
 region

On 9/4/2025 2:54 PM, Sagi Shahar wrote:
[...]
> +
> +void vm_tdx_load_common_boot_parameters(struct kvm_vm *vm)
> +{
> +	struct td_boot_parameters *params =
> +		addr_gpa2hva(vm, TD_BOOT_PARAMETERS_GPA);
> +	uint32_t cr4;
> +
> +	TEST_ASSERT_EQ(vm->mode, VM_MODE_PXXV48_4K);
> +
> +	cr4 = kvm_get_default_cr4();
> +
> +	/* TDX spec 11.6.2: CR4 bit MCE is fixed to 1 */
> +	cr4 |= X86_CR4_MCE;
> +
> +	/* Set this because UEFI also sets this up, to handle XMM exceptions */

I don't get it.
Could you elaborate it a bit?

> +	cr4 |= X86_CR4_OSXMMEXCPT;
> +
> +	/* TDX spec 11.6.2: CR4 bit VMXE and SMXE are fixed to 0 */
> +	cr4 &= ~(X86_CR4_VMXE | X86_CR4_SMXE);
> +
> +	/* Set parameters! */
> +	params->cr0 = kvm_get_default_cr0();
> +	params->cr3 = vm->pgd;
> +	params->cr4 = cr4;
> +	params->idtr.base = vm->arch.idt;
> +	params->idtr.limit = kvm_get_default_idt_limit();
> +	params->gdtr.base = vm->arch.gdt;
> +	params->gdtr.limit = kvm_get_default_gdt_limit();
> +
> +	TEST_ASSERT(params->cr0 != 0, "cr0 should not be 0");
> +	TEST_ASSERT(params->cr3 != 0, "cr3 should not be 0");
> +	TEST_ASSERT(params->cr4 != 0, "cr4 should not be 0");
> +	TEST_ASSERT(params->gdtr.base != 0, "gdt base address should not be 0");
> +	TEST_ASSERT(params->idtr.base != 0, "idt base address should not be 0");
> +}
> +
[...]