On 15/01/2015 11:25, Frederic Konrad wrote: > Hi everybody, > > In case of multithread TCG what is the best way to handle > qemu_global_mutex? > We though to have one mutex per vcpu and then synchronize vcpu threads when > they exit (eg: in tcg_exec_all).
The basic ideas from Jan's patch in http://article.gmane.org/gmane.comp.emulators.qemu/118807 still apply. RAM block reordering doesn't exist anymore, having been replaced with mru_block. The patch reacquired the lock when entering MMIO or PIO emulation. That's enough while there is only one VCPU thread. Once you have >1 VCPU thread you'll need the RCU work that I am slowly polishing and sending out. That's because one device can change the memory map, and that will cause a tlb_flush for all CPUs in tcg_commit, and that's not thread-safe. And later on, once devices start being converted to run outside the BQL, that can be changed to use new functions address_space_rw_unlocked / io_mem_read_unlocked / io_mem_write_unlocked. Something like that is already visible at https://github.com/bonzini/qemu/commits/rcu (ignore patches after "kvm: Switch to unlocked MMIO"). Paolo
