[PATCH v2 1/7] qemu_tpm: Do async IO when starting swtpm emulator

Michal Privoznik mprivozn at redhat.com
Tue Mar 22 16:02:00 UTC 2022

When vTPM is secured via virSecret libvirt passes the secret
value via an FD when swtpm is started (arguments --key and
--migration-key). The writing of the secret into the FDs is
handled via virCommand, specifically qemu_tpm calls
virCommandSetSendBuffer()) and then virCommandRunAsync() spawns a
thread to handle writing into the FD via
virCommandDoAsyncIOHelper. But the thread is not created unless
VIR_EXEC_ASYNC_IO flag is set, which it isn't. In order to fix
it, virCommandDoAsyncIO() must be called.

The credit goes to Marc-André Lureau
<marcandre.lureau at redhat.com> who has done all the debugging and
proposed fix in the bugzilla.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2064115
Fixes: a9c500d2b50c5c041a1bb6ae9724402cf1cec8fe
Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
 src/qemu/qemu_tpm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/qemu/qemu_tpm.c b/src/qemu/qemu_tpm.c
index 50f9caabf3..56bccee128 100644
--- a/src/qemu/qemu_tpm.c
+++ b/src/qemu/qemu_tpm.c
@@ -899,6 +899,7 @@ qemuTPMEmulatorStart(virQEMUDriver *driver,
     if (!(pidfile = qemuTPMEmulatorPidFileBuildPath(cfg->swtpmStateDir, shortName)))
         return -1;
+    virCommandDoAsyncIO(cmd);
     virCommandSetPidFile(cmd, pidfile);
     virCommandSetErrorFD(cmd, &errfd);

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