Re: [PATCH] tpm_emulator: Report an error if chardev is missing

[Stefan Berger]

On 7/24/20 10:00 AM, Markus Armbruster wrote:

Stefan Berger <stef...@linux.vnet.ibm.com> writes:

This patch fixes the odd error reporting when trying to send a file
descriptor to the TPM emulator if one has not passed a valid chardev.

$ x86_64-softmmu/qemu-system-x86_64 -tpmdev emulator,id=tpm0
qemu-system-x86_64: -tpmdev emulator,id=tpm0: tpm-emulator: Failed to send 
CMD_SET_DATAFD: Success
qemu-system-x86_64: -tpmdev emulator,id=tpm0: tpm-emulator: Could not cleanly 
shutdown the TPM: Success

This is the new error report:

$ x86_64-softmmu/qemu-system-x86_64 -tpmdev emulator,id=tpm0
qemu-system-x86_64: -tpmdev emulator,id=tpm0: tpm-emulator: missing chardev

                                                 ~~~~~~~~~~~~~~

The "tpm-emulator: " part looks superfluous.

Hmm, many error messages in this file have it.  Feel free to keep it
now for consistency, and clean it up later.

We usually report missing option parameters like "parameter 'chardev' is
missing".  Please consider sticking to that.

Fixed.

This change does not hide the display of supported TPM types if a non-existent 
type is passed:

$ x86_64-softmmu/qemu-system-x86_64 -tpmdev nonexistent,id=tpm0
qemu-system-x86_64: -tpmdev nonexistent,id=tpm0: Parameter 'type' expects a TPM 
backend type
Supported TPM types (choose only one):
  passthrough   Passthrough TPM backend driver
     emulator   TPM emulator backend driver

Signed-off-by: Stefan Berger <stef...@linux.ibm.com>
---
  backends/tpm/tpm_emulator.c | 8 ++++++++
  1 file changed, 8 insertions(+)

diff --git a/backends/tpm/tpm_emulator.c b/backends/tpm/tpm_emulator.c
index 9605339f93..55cbc9c60e 100644
--- a/backends/tpm/tpm_emulator.c
+++ b/backends/tpm/tpm_emulator.c
@@ -568,6 +568,9 @@ static int tpm_emulator_handle_device_opts(TPMEmulator 
*tpm_emu, QemuOpts *opts)
          }

tpm_emu->options->chardev = g_strdup(value);

+    } else {
+        error_report("tpm-emulator: missing chardev");
+        goto err;
      }

if (tpm_emulator_prepare_data_fd(tpm_emu) < 0) {

This is minimally invasive.

I'd prefer

        Error *err = NULL;
        const char *value;
        Chardev *dev;

        value = qemu_opt_get(opts, "chardev");
        if (!value) {
            error_report("tpm-emulator: missing chardev");
            goto err;
        }

        dev = qemu_chr_find(value);
        if (!dev) {
            error_report("tpm-emulator: tpm chardev '%s' not found.", value);
            goto err;
        }

Your choice.

Ok, changed it to this.

@@ -925,6 +928,11 @@ static void tpm_emulator_shutdown(TPMEmulator *tpm_emu)
  {
      ptm_res res;

+ if (!tpm_emu->options->chardev) {

+        /* was never properly initialized */
+        return;
+    }
+

Is this still reachable?  If yes, how?

tpm_emulator_inst_finalize still runs.


Sending V2. Thanks.

If not, drop the hunk and have my
Reviewed-by: Markus Armbruster <arm...@redhat.com>

      if (tpm_emulator_ctrlcmd(tpm_emu, CMD_SHUTDOWN, &res, 0, sizeof(res)) < 
0) {
          error_report("tpm-emulator: Could not cleanly shutdown the TPM: %s",
                       strerror(errno));