[PATCH 6/9] KVM: x86: Provide paravirtualized flush_tlb_multi()

[Nadav Amit]

Support the new interface of flush_tlb_multi, which also flushes the
local CPU's TLB, instead of flush_tlb_others that does not. This
interface is more performant since it parallelize remote and local TLB
flushes.

The actual implementation of flush_tlb_multi() is almost identical to
that of flush_tlb_others().

Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: k...@vger.kernel.org
Signed-off-by: Nadav Amit <na...@vmware.com>
---
 arch/x86/kernel/kvm.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 00d81e898717..d00d551d4a2a 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -580,7 +580,7 @@ static void __init kvm_apf_trap_init(void)
 
 static DEFINE_PER_CPU(cpumask_var_t, __pv_tlb_mask);
 
-static void kvm_flush_tlb_others(const struct cpumask *cpumask,
+static void kvm_flush_tlb_multi(const struct cpumask *cpumask,
                        const struct flush_tlb_info *info)
 {
        u8 state;
@@ -594,6 +594,11 @@ static void kvm_flush_tlb_others(const struct cpumask 
*cpumask,
         * queue flush_on_enter for pre-empted vCPUs
         */
        for_each_cpu(cpu, flushmask) {
+               /*
+                * The local vCPU is never preempted, so we do not explicitly
+                * skip check for local vCPU - it will never be cleared from
+                * flushmask.
+                */
                src = &per_cpu(steal_time, cpu);
                state = READ_ONCE(src->preempted);
                if ((state & KVM_VCPU_PREEMPTED)) {
@@ -603,7 +608,7 @@ static void kvm_flush_tlb_others(const struct cpumask 
*cpumask,
                }
        }
 
-       native_flush_tlb_others(flushmask, info);
+       native_flush_tlb_multi(flushmask, info);
 }
 
 static void __init kvm_guest_init(void)
@@ -628,9 +633,8 @@ static void __init kvm_guest_init(void)
        if (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
            !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
            kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
-               pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
+               pv_ops.mmu.flush_tlb_multi = kvm_flush_tlb_multi;
                pv_ops.mmu.tlb_remove_table = tlb_remove_table;
-               static_key_disable(&flush_tlb_multi_enabled.key);
        }
 
        if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
-- 
2.20.1