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

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Message-ID: <CAAhR5DG6EDP=25-SrmBnbKYbrwH=bCP2f6OPO8KE=oXQxVBXbQ@mail.gmail.com>
Date: Thu, 21 Aug 2025 17:24:56 -0500
From: Sagi Shahar <sagis@...gle.com>
To: Ira Weiny <ira.weiny@...el.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>, 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>, Chao Gao <chao.gao@...el.com>, 
	Chenyi Qiang <chenyi.qiang@...el.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v9 04/19] KVM: selftests: Expose function to allocate
 guest vCPU stack

On Thu, Aug 21, 2025 at 4:58 PM Ira Weiny <ira.weiny@...el.com> wrote:
>
> 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?
>

I double checked and no one is creating VMs with KVM_X86_TDX_VM. The
first test that sets KVM_X86_TDX_VM is the last patch in the series.

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