linux-kernel - Re: [PATCH v8 07/30] KVM: selftests: TDX: Use KVM_TDX_CAPABILITIES to validate TDs' attribute configuration

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Message-ID: <CAAhR5DHh2vw_UkOexGSmGMnzXww-n5exgUHp3bb5debjY9suww@mail.gmail.com>
Date: Wed, 20 Aug 2025 16:49:22 -0500
From: Sagi Shahar <sagis@...gle.com>
To: Chenyi Qiang <chenyi.qiang@...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>, Ira Weiny <ira.weiny@...el.com>, 
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v8 07/30] KVM: selftests: TDX: Use KVM_TDX_CAPABILITIES to
 validate TDs' attribute configuration

On Wed, Aug 20, 2025 at 4:18 PM Sagi Shahar <sagis@...gle.com> wrote:
>
> On Wed, Aug 13, 2025 at 8:34 AM Chenyi Qiang <chenyi.qiang@...el.com> wrote:
> >
> >
> >
> > On 8/8/2025 4:16 AM, Sagi Shahar wrote:
> > > From: Ackerley Tng <ackerleytng@...gle.com>
> > >
> > > This also exercises the KVM_TDX_CAPABILITIES ioctl.
> > >
> > > Suggested-by: Isaku Yamahata <isaku.yamahata@...el.com>
> > > Co-developed-by: Isaku Yamahata <isaku.yamahata@...el.com>
> > > Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> > > Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
> > > Signed-off-by: Sagi Shahar <sagis@...gle.com>
> > > ---
> > >  .../selftests/kvm/lib/x86/tdx/tdx_util.c        | 17 +++++++++++++++++
> > >  1 file changed, 17 insertions(+)
> > >
> > > 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 392d6272d17e..bb074af4a476 100644
> > > --- a/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> > > +++ b/tools/testing/selftests/kvm/lib/x86/tdx/tdx_util.c
> > > @@ -140,6 +140,21 @@ static void tdx_apply_cpuid_restrictions(struct kvm_cpuid2 *cpuid_data)
> > >       }
> > >  }
> > >
> > > +static void tdx_check_attributes(struct kvm_vm *vm, uint64_t attributes)
> > > +{
> > > +     struct kvm_tdx_capabilities *tdx_cap;
> > > +
> > > +     tdx_cap = tdx_read_capabilities(vm);
> > > +
> > > +     /* TDX spec: any bits 0 in supported_attrs must be 0 in attributes */
> > > +     TEST_ASSERT_EQ(attributes & ~tdx_cap->supported_attrs, 0);
> > > +
> > > +     /* TDX spec: any bits 1 in attributes must be 1 in supported_attrs */
> > > +     TEST_ASSERT_EQ(attributes & tdx_cap->supported_attrs, attributes);
> > > +
> > > +     free(tdx_cap);
> > > +}
> > > +
> > >  #define KVM_MAX_CPUID_ENTRIES 256
> > >
> > >  #define CPUID_EXT_VMX                        BIT(5)
> > > @@ -256,6 +271,8 @@ static void tdx_td_init(struct kvm_vm *vm, uint64_t attributes)
> > >       memcpy(&init_vm->cpuid, cpuid, kvm_cpuid2_size(cpuid->nent));
> > >       free(cpuid);
> > >
> > > +     tdx_check_attributes(vm, attributes);
> > > +
> > >       init_vm->attributes = attributes;
> > >
> > >       tdx_apply_cpuid_restrictions(&init_vm->cpuid);
> >
> > Do we need to set the init_vm->xfam based on cpuid.0xd and validate it with tdx_cap->supported_xfam?
> >
> I don't think it's necessary. And according to the TDX spec (TDX
> Module Base Spec - 11.8.3. Extended Features Execution Control) the
> mapping from CPUID to XFAM is not trivial. Checking attributes makes
> sense since some tests use non-default attributes but right now we
> don't have any test which uses XFAM features. We can add XFAM support
> in the future if it's needed and do the check then.

I just saw the comment on "KVM: selftests: TDX: Add basic TDX CPUID
test" which suggests adding xfam support. I can add a check for xfam
when I rework that patch but I still think that the values for xfam
should come from the test and validated here instead of being
calculated based on cpuid.