[PATCH] libacpi: Widen TPM detection

[PATCH] libacpi: Widen TPM detection

[Jason Andryuk]

The hardcoded tpm_signature is too restrictive to detect many TPMs.  For
instance, it doesn't accept a QEMU emulated TPM (VID 0x1014 DID 0x0001).
Make the TPM detection match that in rombios which accepts a wider
range.

With this change, the TPM's TCPA ACPI table is generated and the guest
OS can automatically load the tpm_tis driver.  It also allows seabios to
detect and use the TPM.  However, seabios skips some TPM initialization
when running under Xen, so it will not populate any PCRs unless modified
to run the initialization under Xen.

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
---
 tools/libacpi/build.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/libacpi/build.c b/tools/libacpi/build.c
index fa7d14e090..a61dd5583a 100644
--- a/tools/libacpi/build.c
+++ b/tools/libacpi/build.c
@@ -351,7 +351,6 @@ static int construct_secondary_tables(struct acpi_ctxt *ctxt,
     struct acpi_20_waet *waet;
     struct acpi_20_tcpa *tcpa;
     unsigned char *ssdt;
-    static const uint16_t tis_signature[] = {0x0001, 0x0001, 0x0001};
     void *lasa;
 
     /* MADT. */
@@ -413,9 +412,8 @@ static int construct_secondary_tables(struct acpi_ctxt *ctxt,
 
     /* TPM TCPA and SSDT. */
     if ( (config->table_flags & ACPI_HAS_TCPA) &&
-         (config->tis_hdr[0] == tis_signature[0]) &&
-         (config->tis_hdr[1] == tis_signature[1]) &&
-         (config->tis_hdr[2] == tis_signature[2]) )
+         (config->tis_hdr[0] != 0 && config->tis_hdr[0] != 0xffff) &&
+         (config->tis_hdr[1] != 0 && config->tis_hdr[1] != 0xffff) )
     {
         ssdt = ctxt->mem_ops.alloc(ctxt, sizeof(ssdt_tpm), 16);
         if (!ssdt) return -1;
-- 
2.25.1

Re: [PATCH] libacpi: Widen TPM detection

[Andrew Cooper]

On 11/06/2020 04:55, Jason Andryuk wrote:
> The hardcoded tpm_signature is too restrictive to detect many TPMs.  For
> instance, it doesn't accept a QEMU emulated TPM (VID 0x1014 DID 0x0001).
> Make the TPM detection match that in rombios which accepts a wider
> range.
>
> With this change, the TPM's TCPA ACPI table is generated and the guest
> OS can automatically load the tpm_tis driver.  It also allows seabios to
> detect and use the TPM.  However, seabios skips some TPM initialization
> when running under Xen, so it will not populate any PCRs unless modified
> to run the initialization under Xen.
>
> Signed-off-by: Jason Andryuk <jandryuk@gmail.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

This looks like it wants backporting, so CC'ing Paul for a 4.14 release ack.

RE: [PATCH] libacpi: Widen TPM detection

[Paul Durrant]

> -----Original Message-----
> From: Andrew Cooper <andrew.cooper3@citrix.com>
> Sent: 11 June 2020 12:52
> To: Jason Andryuk <jandryuk@gmail.com>; xen-devel@lists.xenproject.org
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>; Wei Liu <wl@xen.org>; Jan Beulich <jbeulich@suse.com>;
> Paul Durrant <paul@xen.org>
> Subject: Re: [PATCH] libacpi: Widen TPM detection
> 
> On 11/06/2020 04:55, Jason Andryuk wrote:
> > The hardcoded tpm_signature is too restrictive to detect many TPMs.  For
> > instance, it doesn't accept a QEMU emulated TPM (VID 0x1014 DID 0x0001).
> > Make the TPM detection match that in rombios which accepts a wider
> > range.
> >
> > With this change, the TPM's TCPA ACPI table is generated and the guest
> > OS can automatically load the tpm_tis driver.  It also allows seabios to
> > detect and use the TPM.  However, seabios skips some TPM initialization
> > when running under Xen, so it will not populate any PCRs unless modified
> > to run the initialization under Xen.
> >
> > Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
> 
> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
> 
> This looks like it wants backporting, so CC'ing Paul for a 4.14 release ack.

Agreed.

Release-acked-by: Paul Durrant <paul@xen.org>