[libvirt] [PATCH] tpm: adapt sysfs cancel path for new TPM driver

[Stefan Berger]

Adapt the sysfs TPM command cancel path for the TPM driver that
does not use a miscdevice anymore since Linux 4.0. Support old
and new paths.

Signed-off-by: Stefan Berger <stefanb at linux.vnet.ibm.com>
---
 src/util/virtpm.c                                   | 21 +++++++++++++++++++--
 .../qemuxml2argv-tpm-passthrough.args               |  2 +-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/util/virtpm.c b/src/util/virtpm.c
index 88f8361..40a758b 100644
--- a/src/util/virtpm.c
+++ b/src/util/virtpm.c
@@ -23,9 +23,12 @@
 #include <config.h>
 
 #include <sys/stat.h>
+#include <fcntl.h>
 
 #include "virstring.h"
 #include "virerror.h"
+#include "viralloc.h"
+#include "virfile.h"
 #include "virtpm.h"
 
 #define VIR_FROM_THIS VIR_FROM_NONE
@@ -41,13 +44,27 @@ virTPMCreateCancelPath(const char *devpath)
 {
     char *path = NULL;
     const char *dev;
+    const char *prefix[] = {"misc/", "tpm/"};
+    int i, fd;
 
     if (devpath) {
         dev = strrchr(devpath, '/');
         if (dev) {
             dev++;
-            if (virAsprintf(&path, "/sys/class/misc/%s/device/cancel",
-                            dev) < 0)
+            for (i = 0; i < ARRAY_CARDINALITY(prefix); i++) {
+                if (virAsprintf(&path, "/sys/class/%s%s/device/cancel",
+                                prefix[i], dev) < 0)
+                     goto cleanup;
+
+                fd = open(path, O_WRONLY);
+                if (fd >= 0) {
+                    VIR_FORCE_CLOSE(fd);
+                    break;
+                }
+                VIR_FREE(path);
+            }
+            /* /dev/null does not allow to cancel cmds but it can be used */
+            if (!path && virAsprintf(&path, "/dev/null") < 0)
                 goto cleanup;
         } else {
             virReportError(VIR_ERR_INTERNAL_ERROR,
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-tpm-passthrough.args b/tests/qemuxml2argvdata/qemuxml2argv-tpm-passthrough.args
index f33120f..1e48603 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-tpm-passthrough.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-tpm-passthrough.args
@@ -17,6 +17,6 @@ QEMU_AUDIO_DRV=none \
 -boot c \
 -usb \
 -tpmdev passthrough,id=tpm-tpm0,path=/dev/tpm0,\
-cancel-path=/sys/class/misc/tpm0/device/cancel \
+cancel-path=/dev/null \
 -device tpm-tis,tpmdev=tpm-tpm0,id=tpm0 \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
-- 
2.4.3