linux-kernel - Re: [PATCH v9 04/19] KVM: selftests: Expose function to allocate guest vCPU stack

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Message-ID: <68a797031c5a6_2be23a29461@iweiny-mobl.notmuch>
Date: Thu, 21 Aug 2025 17:00:35 -0500
From: Ira Weiny <ira.weiny@...el.com>
To: Sagi Shahar <sagis@...gle.com>, <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>, Binbin Wu <binbin.wu@...ux.intel.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>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
Subject: Re: [PATCH v9 04/19] KVM: selftests: Expose function to allocate
 guest vCPU stack

Sagi Shahar wrote:

[snip]

> diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
> index b2a4b11ac8c0..1eae92957456 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -687,12 +687,9 @@ void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
>  	vcpu_regs_set(vcpu, &regs);
>  }
>  
> -struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
> +vm_vaddr_t kvm_allocate_vcpu_stack(struct kvm_vm *vm)
>  {
> -	struct kvm_mp_state mp_state;
> -	struct kvm_regs regs;
>  	vm_vaddr_t stack_vaddr;
> -	struct kvm_vcpu *vcpu;
>  
>  	stack_vaddr = __vm_vaddr_alloc(vm, DEFAULT_STACK_PGS * getpagesize(),
>  				       DEFAULT_GUEST_STACK_VADDR_MIN,
> @@ -713,6 +710,15 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
>  		    "__vm_vaddr_alloc() did not provide a page-aligned address");
>  	stack_vaddr -= 8;
>  
> +	return stack_vaddr;
> +}
> +
> +struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
> +{
> +	struct kvm_mp_state mp_state;
> +	struct kvm_regs regs;
> +	struct kvm_vcpu *vcpu;
> +
>  	vcpu = __vm_vcpu_add(vm, vcpu_id);
>  	vcpu_init_cpuid(vcpu, kvm_get_supported_cpuid());
>  	vcpu_init_sregs(vm, vcpu);
> @@ -721,7 +727,8 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
>  	/* Setup guest general purpose registers */
>  	vcpu_regs_get(vcpu, &regs);
>  	regs.rflags = regs.rflags | 0x2;
> -	regs.rsp = stack_vaddr;
> +	if (vm->type != KVM_X86_TDX_VM)
> +		regs.rsp = kvm_allocate_vcpu_stack(vm);

At this point in the series vm->type can't be KVM_X86_TDX_VM correct?

So that makes this safe during bisect?

Ira

>  	vcpu_regs_set(vcpu, &regs);
>  
>  	/* Setup the MP state */
> -- 
> 2.51.0.rc1.193.gad69d77794-goog
>