tpm: tpm_passthrough: Read the buffer size from the host device

Rather than hard coding the buffer size in the tpm_passthrough
backend read the TPM I/O buffer size from the host device.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/hw/tpm/tpm_passthrough.c b/hw/tpm/tpm_passthrough.c
index daac67d..886af9e 100644
--- a/hw/tpm/tpm_passthrough.c
+++ b/hw/tpm/tpm_passthrough.c
@@ -57,6 +57,7 @@ struct TPMPassthruState {
     int cancel_fd;
 
     TPMVersion tpm_version;
+    size_t tpm_buffersize;
 };
 
 typedef struct TPMPassthruState TPMPassthruState;
@@ -201,7 +202,15 @@ static TPMVersion tpm_passthrough_get_tpm_version(TPMBackend *tb)
 
 static size_t tpm_passthrough_get_buffer_size(TPMBackend *tb)
 {
-    return 4096;
+    TPMPassthruState *tpm_pt = TPM_PASSTHROUGH(tb);
+    int ret;
+
+    ret = tpm_util_get_buffer_size(tpm_pt->tpm_fd, tpm_pt->tpm_version,
+                                   &tpm_pt->tpm_buffersize);
+    if (ret < 0) {
+        tpm_pt->tpm_buffersize = 4096;
+    }
+    return tpm_pt->tpm_buffersize;
 }
 
 /*