On Mon, Jun 04, 2012 at 10:37:24AM +0530, Nikunj A. Dadhania wrote: > flush_tlb_others_ipi depends on lot of statics in tlb.c. Replicated > the flush_tlb_others_ipi as kvm_flush_tlb_others to further adapt to > paravirtualization. > > Use the vcpu state information inside the kvm_flush_tlb_others to > avoid sending ipi to pre-empted vcpus. > > * Do not send ipi's to offline vcpus and set flush_on_enter flag > * For online vcpus: Wait for them to clear the flag > > The approach was discussed here: https://lkml.org/lkml/2012/2/20/157 > > Suggested-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > Signed-off-by: Nikunj A. Dadhania <nikunj@xxxxxxxxxxxxxxxxxx> Why not reintroduce the hypercall to flush TLBs? No waiting, no entry/exit trickery. This is half-way-there paravirt with all the downsides. Even though the guest running information might be useful in other cases. > Pseudo Algo: > > Write() > ====== > > guest_exit() > flush_on_enter[i]=0; > running[i] = 0; > > guest_enter() > running[i] = 1; > smp_mb(); > if(flush_on_enter[i]) { > tlb_flush() > flush_on_enter[i]=0; > } > > > Read() > ====== > > GUEST KVM-HV > > f->flushcpumask = cpumask - me; > > again: > for_each_cpu(i, f->flushmask) { > > if (!running[i]) { > case 1: > > running[n]=1 > > (cpuN does not see > flush_on_enter set, > guest later finds it > running and sends ipi, > we are fine here, need > to clear the flag on > guest_exit) > > flush_on_enter[i] = 1; > case2: > > running[n]=1 > (cpuN - will see flush > on enter and an IPI as > well - addressed in patch-4) > > if (!running[i]) > cpu_clear(f->flushmask); All is well, vm_enter > will do the fixup > } > case 3: > running[n] = 0; > > (cpuN went to sleep, > we saw it as awake, > ipi sent, but wait > will break without > zero_mask and goto > again will take care) > > } > send_ipi(f->flushmask) > > wait_a_while_for_zero_mask(); > > if (!zero_mask) > goto again; > --- > arch/x86/include/asm/kvm_para.h | 3 +- > arch/x86/include/asm/tlbflush.h | 9 ++++++ > arch/x86/kernel/kvm.c | 1 + > arch/x86/kvm/x86.c | 14 ++++++++- > arch/x86/mm/tlb.c | 61 +++++++++++++++++++++++++++++++++++++++ > 5 files changed, 86 insertions(+), 2 deletions(-) > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
