On Monday 28 July 2008 12:33:41 Liu Yu wrote: > I have a question that I could not think through. > While multiple qemu/kvm processes are running at the same time, how to > prevent one guest from using others' TLB? For all the guests have the > same TID=0 for userspace and TID=1 for kernel. [...]
Hi Yu Liu, thats a good question. Afaik thats solved by the fact that the shadow tlb which is used when entering guest context is per vcpu. Therefor a guest has always it's own shadow tlb active and no mappings to the content of other guests. This patch just allows us that a single guest userspace process accessing the kernel 20 times (and changing privilege level 20 times by doing so) can run without tlb flushes. Guest-userspace context switch (pid is changing) -> tlb flush; and guest switches (guest A -> guest B) -> other shadow tlb active; should still be working fine. > > > > The net is that we don't need to flush the TLB on privilege > > switches, but we do on guest context switches (which are far > > more infrequent). Guest boot time performance improvement: about 30%. > > -- Grüsse / regards, Christian Ehrhardt IBM Linux Technology Center, Open Virtualization -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
