bhyve: add execution command for tpm devices

[corvink]

Summary

Executing a tpm command is as easy as writing the command to the tpm fd and reading back the result.

[markj]

usr.sbin/bhyve/tpm_emul_passthru.c

71

Should you check rsp_size >= sizeof(struct tpm_resp_hdr) before doing anything?

74

rsp_size is unsigned, the last format should be %u. I'm surprised the compiler doesn't warn about it.

[corvink]

• address markj's feedback

[markj]

usr.sbin/bhyve/tpm_emul_passthru.c

71

78