Add a TPM Passthrough backend driver implementation

This patch is based of off version 9 of Stefan Berger's patch series
  "QEMU Trusted Platform Module (TPM) integration"
and adds a new backend driver for it.

This patch adds a passthrough backend driver for passing commands sent to the
emulated TPM device directly to a TPM device opened on the host machine.
Thus it is possible to use a hardware TPM device in a system running on QEMU,
providing the ability to access a TPM in a special state (e.g. after a Trusted
Boot).

This functionality is being used in the acTvSM Trusted Virtualization Platform
which is available on [1].

Usage example:
  qemu-system-x86_64 -tpmdev passthrough,id=tpm0,path=/dev/tpm0 \
                     -device tpm-tis,tpmdev=tpm0 \
                     -cdrom test.iso -boot d

Some notes about the host TPM:
The TPM needs to be enabled and activated. If that's not the case one
has to go through the BIOS/UEFI and enable and activate that TPM for TPM
commands to work as expected.
It may be necessary to boot the kernel using tpm_tis.force=1 in the boot
command line or 'modprobe tpm_tis force=1' in case of using it as a module.

Regards,
Andreas Niederl, Stefan Berger

[1] http://trustedjava.sourceforge.net/

Signed-off-by: Andreas Niederl <andreas.niederl@iaik.tugraz.at>
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Corey Bryant <coreyb@linux.vnet.ibm.com>
Reviewed-by: Joel Schopp <jschopp@linux.vnet.ibm.com>
Message-id: 1361987275-26289-6-git-send-email-stefanb@linux.vnet.ibm.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/qemu-char.c b/qemu-char.c
index 04aa589c7e..83787c74c4 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -533,6 +533,30 @@ int send_all(int fd, const void *_buf, int len1)
     }
     return len1 - len;
 }
+
+int recv_all(int fd, void *_buf, int len1, bool single_read)
+{
+    int ret, len;
+    uint8_t *buf = _buf;
+
+    len = len1;
+    while ((len > 0) && (ret = read(fd, buf, len)) != 0) {
+        if (ret < 0) {
+            if (errno != EINTR && errno != EAGAIN) {
+                return -1;
+            }
+            continue;
+        } else {
+            if (single_read) {
+                return ret;
+            }
+            buf += ret;
+            len -= ret;
+        }
+    }
+    return len1 - len;
+}
+
 #endif /* !_WIN32 */
 
 typedef struct IOWatchPoll