[libvirt] "Unable to read QEMU help output: Interrupted system call" doing virDomainRestore() on current master

Howdy. I've had this issue since yesterday, but avoided reporting it until determining today that it occurs on an unmodified upstream tree as well as my own local branch: $ virsh restore ramsave error: Failed to restore domain from ramsave error: Unable to read QEMU help output: Interrupted system call This happens immediately (no delay) and only on restore; "virsh start" behaves as usual. When running libvirtd under gdb, the failure mode is different: $ virsh restore ramsave error: Failed to restore domain from ramsave error: internal error Timed out while reading monitor startup output When running libvirtd under strace, this shows the binary being run (["/usr/bin/qemu-kvm", "-help"]) failing with a SIGPIPE while attempting to write to stdout. strace also shows a SIGSEGV being delivered to a libvirtd thread (a few clone()s removed from the parent) after that thread attempts to close all its open file descriptors above 0-2, but without being able to run gdb I'm at a bit of a loss as to what that thread is doing. Any suggestions?