linux-kernel - Re: [PATCH v11 13/21] KVM: selftests: Add helpers to init TDX memory and finalize VM

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Message-ID: <CAAhR5DFJKTTY3tN7AU=BXDRJAGjuortmK0ruQWU8RB_Z6jVugQ@mail.gmail.com>
Date: Fri, 24 Oct 2025 11:45:36 -0500
From: Sagi Shahar <sagis@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Ira Weiny <ira.weiny@...el.com>, linux-kselftest@...r.kernel.org, 
	Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, 
	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 v11 13/21] KVM: selftests: Add helpers to init TDX memory
 and finalize VM

On Fri, Oct 24, 2025 at 11:02 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Thu, Oct 23, 2025, Sagi Shahar wrote:
> > On Wed, Oct 15, 2025 at 11:25 AM Ira Weiny <ira.weiny@...el.com> wrote:
> > >
> > > Sagi Shahar wrote:
> > > > From: Ackerley Tng <ackerleytng@...gle.com>
> > > >
> > >
> > > [snip]
> > >
> > > > diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> > > > index 2551b3eac8f8..53cfadeff8de 100644
> > > > --- a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> > > > +++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> > > > @@ -270,3 +270,61 @@ void vm_tdx_init_vm(struct kvm_vm *vm, uint64_t attributes)
> > > >
> > > >       free(init_vm);
> > > >  }
> > > > +
> > >
> > > [snip]
> > >
> > > > +
> > > > +void vm_tdx_finalize(struct kvm_vm *vm)
> > >
> > > Why is this not a new kvm_arch_vm_finalize_vcpu() call?
> >
> > What do you mean?
>
> Ira is pointing out that upstream now has kvm_arch_vm_finalize_vcpus(), so you
> can (and I agree, should) implement that for x86.c, and do vm_tdx_finalize() from
> there (based on the VM shape) instead of requiring the caller to manually finalize
> the TD.
>
> Unlike SEV, where userspace can manipulate guest state prior to LAUNCH, TDX guest
> state is unreachable from time zero, i.e. there is unlikely to be many (any?) use
> cases where a selftest wants to do something between creating vCPUs and finalizing
> the TD.

There are actually a few use cases for calling vm_tdx_finalize
seperately from the create phase. One such case is when a user wants
to add additional memslots for testing shared memory conversions.
Another one is installing interrupt handlers. But these are probably
rare enough that they can call __vm_create() and vm_vcpu_add()
manually instead of using the wrapper