Hi Marcelo, Thanks for the review.
On Tue, 12 Jun 2012 20:02:18 -0300, Marcelo Tosatti <[email protected]> wrote: > 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 <[email protected]> > > Signed-off-by: Nikunj A. Dadhania <[email protected]> > > Why not reintroduce the hypercall to flush TLBs? Sure, I will get a version with this. > No waiting, no entry/exit trickery. > Are you also suggesting to get rid of vcpu-running information? We would atleast need this to raise a flushTLB hypercall on the sleeping vcpu. > This is half-way-there paravirt with all the downsides. Some more details on what are the downsides would help us reach to a better solution. > Even though the guest running information might be useful in other > cases. > Yes, that was one of the things on the mind. > > 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 [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- 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
