Re: [Qemu-devel] [PATCH v3 4/4] tpm: add a fake ACPI memory clear interface

[Igor Mammedov]

On Thu, 21 Jun 2018 15:24:44 +0200
Marc-André Lureau <address@hidden> wrote:

> Hi
> 
> On Thu, Jun 21, 2018 at 3:02 PM, Igor Mammedov <address@hidden> wrote:
> > On Tue, 15 May 2018 14:14:33 +0200
> > Marc-André Lureau <address@hidden> wrote:
> >  
> >> This allows to pass the last failing test from the Windows HLK TPM 2.0
> >> TCG PPI 1.3 tests.
> >>
> >> The interface is described in the "TCG Platform Reset Attack
> >> Mitigation Specification", chapter 6 "ACPI _DSM Function". Whether or
> >> not we should have a real implementation remains an open question to me.  
> > might it cause security issues?  
> 
> Good question. If the guest assumes success of this operation perhaps.
> I'll check the spec.
> 
> > What are implications of faking it and how hard it's to implement thing
> > per spec?  
> 
> Laszlo answerd that in "[Qemu-devel] investigating TPM for
> OVMF-on-QEMU"  2f2b) TCG Memory Clear Interface
I get that it's optional, but we probably shouldn't advertise/fake
feature if it's not supported.

> 
> >
> >  
> >> Signed-off-by: Marc-André Lureau <address@hidden>
> >> ---
> >>  hw/i386/acpi-build.c | 9 +++++++++
> >>  1 file changed, 9 insertions(+)
> >>
> >> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> >> index 95be4f0710..392a1e50bd 100644
> >> --- a/hw/i386/acpi-build.c
> >> +++ b/hw/i386/acpi-build.c
> >> @@ -2072,6 +2072,15 @@ build_tpm_ppi(Aml *dev)
> >>              aml_append(ifctx, aml_return(aml_buffer(1, zerobyte)));
> >>          }
> >>          aml_append(method, ifctx);
> >> +
> >> +       /* dummy MOR Memory Clear for the sake of WLK PPI test */
> >> +        ifctx = aml_if(
> >> +            aml_equal(aml_arg(0),
> >> +                      
> >> aml_touuid("376054ED-CC13-4675-901C-4756D7F2D45D")));
> >> +        {
> >> +            aml_append(ifctx, aml_return(aml_int(0)));
> >> +        }
> >> +        aml_append(method, ifctx);
> >>      }
> >>      aml_append(dev, method);
> >>  }  
> >
> >  
> 
> 
>