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qemu: Pass file descriptor when using TPM passthrough

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Pass the TPM file descriptor to QEMU via command line.
Instead of passing /dev/tpm0 we now pass /dev/fdset/10 and the additional
parameters -add-fd set=10,fd=20.

This addresses the use case when QEMU is started with non-root privileges
and QEMU cannot open /dev/tpm0 for example.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
This commit is contained in:
Stefan Berger 2015-03-05 18:57:06 -05:00
parent 42bee147fe
commit 9954a8bfc2
1 changed files with 117 additions and 4 deletions
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121
src/qemu/qemu_command.c
View File

@ -160,6 +160,58 @@ VIR_ENUM_IMPL(qemuNumaPolicy, VIR_DOMAIN_NUMATUNE_MEM_LAST,
"preferred",
"interleave");
/**
* qemuVirCommandGetFDSet:
* @cmd: the command to modify
* @fd: fd to reassign to the child
*
* Get the parameters for the QEMU -add-fd command line option
* for the given file descriptor. The file descriptor must previously
* have been 'transferred' in a virCommandPassFD() call.
* This function for example returns "set=10,fd=20".
*/
static char *
qemuVirCommandGetFDSet(virCommandPtr cmd, int fd)
{
char *result = NULL;
int idx = virCommandPassFDGetFDIndex(cmd, fd);
if (idx >= 0) {
ignore_value(virAsprintf(&result, "set=%d,fd=%d", idx, fd));
} else {
virReportError(VIR_ERR_INTERNAL_ERROR,
_("file descriptor %d has not been transferred"), fd);
}
return result;
}
/**
* qemuVirCommandGetDevSet:
* @cmd: the command to modify
* @fd: fd to reassign to the child
*
* Get the parameters for the QEMU path= parameter where a file
* descriptor is accessed via a file descriptor set, for example
* /dev/fdset/10. The file descriptor must previously have been
* 'transferred' in a virCommandPassFD() call.
*/
static char *
qemuVirCommandGetDevSet(virCommandPtr cmd, int fd)
{
char *result = NULL;
int idx = virCommandPassFDGetFDIndex(cmd, fd);
if (idx >= 0) {
ignore_value(virAsprintf(&result, "/dev/fdset/%d", idx));
} else {
virReportError(VIR_ERR_INTERNAL_ERROR,
_("file descriptor %d has not been transferred"), fd);
}
return result;
}
/**
* qemuPhysIfaceConnect:
* @def: the definition of the VM (needed by 802.1Qbh and audit)
@ -6322,15 +6374,20 @@ qemuBuildRNGDevStr(virDomainDefPtr def,
static char *qemuBuildTPMBackendStr(const virDomainDef *def,
virCommandPtr cmd,
virQEMUCapsPtr qemuCaps,
const char *emulator)
const char *emulator,
int *tpmfd, int *cancelfd)
{
const virDomainTPMDef *tpm = def->tpm;
virBuffer buf = VIR_BUFFER_INITIALIZER;
const char *type = virDomainTPMBackendTypeToString(tpm->type);
char *cancel_path;
char *cancel_path = NULL, *devset = NULL;
const char *tpmdev;
*tpmfd = -1;
*cancelfd = -1;
virBufferAsprintf(&buf, "%s,id=tpm-%s", type, tpm->info.alias);
switch (tpm->type) {
@ -6342,11 +6399,42 @@ static char *qemuBuildTPMBackendStr(const virDomainDef *def,
if (!(cancel_path = virTPMCreateCancelPath(tpmdev)))
goto error;
if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_ADD_FD)) {
*tpmfd = open(tpmdev, O_RDWR);
if (*tpmfd < 0) {
virReportSystemError(errno, _("Could not open TPM device %s"),
tpmdev);
goto error;
}
virCommandPassFD(cmd, *tpmfd,
VIR_COMMAND_PASS_FD_CLOSE_PARENT);
devset = qemuVirCommandGetDevSet(cmd, *tpmfd);
if (devset == NULL)
goto error;
*cancelfd = open(cancel_path, O_WRONLY);
if (*cancelfd < 0) {
virReportSystemError(errno,
_("Could not open TPM device's cancel "
"path %s"), cancel_path);
goto error;
}
VIR_FREE(cancel_path);
virCommandPassFD(cmd, *cancelfd,
VIR_COMMAND_PASS_FD_CLOSE_PARENT);
cancel_path = qemuVirCommandGetDevSet(cmd, *cancelfd);
if (cancel_path == NULL)
goto error;
}
virBufferAddLit(&buf, ",path=");
virBufferEscape(&buf, ',', ",", "%s", tpmdev);
virBufferEscape(&buf, ',', ",", "%s", devset ? devset : tpmdev);
virBufferAddLit(&buf, ",cancel-path=");
virBufferEscape(&buf, ',', ",", "%s", cancel_path);
VIR_FREE(devset);
VIR_FREE(cancel_path);
break;
@ -6366,6 +6454,9 @@ static char *qemuBuildTPMBackendStr(const virDomainDef *def,
emulator, type);
error:
VIR_FREE(devset);
VIR_FREE(cancel_path);
virBufferFreeAndReset(&buf);
return NULL;
}
@ -8199,13 +8290,35 @@ qemuBuildTPMCommandLine(virDomainDefPtr def,
const char *emulator)
{
char *optstr;
int tpmfd = -1;
int cancelfd = -1;
char *fdset;
if (!(optstr = qemuBuildTPMBackendStr(def, qemuCaps, emulator)))
if (!(optstr = qemuBuildTPMBackendStr(def, cmd, qemuCaps, emulator,
&tpmfd, &cancelfd)))
return -1;
virCommandAddArgList(cmd, "-tpmdev", optstr, NULL);
VIR_FREE(optstr);
if (tpmfd >= 0) {
fdset = qemuVirCommandGetFDSet(cmd, tpmfd);
if (!fdset)
return -1;
virCommandAddArgList(cmd, "-add-fd", fdset, NULL);
VIR_FREE(fdset);
}
if (cancelfd >= 0) {
fdset = qemuVirCommandGetFDSet(cmd, cancelfd);
if (!fdset)
return -1;
virCommandAddArgList(cmd, "-add-fd", fdset, NULL);
VIR_FREE(fdset);
}
if (!(optstr = qemuBuildTPMDevStr(def, qemuCaps, emulator)))
return -1;