[PATCH v2 1/5] KVM: x86: hyperv: optimize 'all cpus' case in kvm_hv_flush_tlb()

Vitaly Kuznetsov
2018-06-28T13:53:09Z

We can use 'NULL' to represent 'all cpus' case in
kvm_make_vcpus_request_mask() and avoid building vCPU mask with
all vCPUs.

Suggested-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/hyperv.c | 42 +++++++++++++++++++++++-------------------
virt/kvm/kvm_main.c | 6 ++----
2 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index af8caf965baa..63a17bbbf0e5 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1310,35 +1310,39 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,

cpumask_clear(&hv_current->tlb_lush);

+ if (all_cpus) {
+ kvm_make_vcpus_request_mask(kvm,
+ KVM_REQ_TLB_FLUSH | KVM_REQUEST_NO_WAKEUP,
+ NULL, &hv_current->tlb_lush);
+ goto ret_success;
+ }
+
kvm_for_each_vcpu(i, vcpu, kvm) {
struct kvm_vcpu_hv *hv = &vcpu->arch.hyperv;
int bank = hv->vp_index / 64, sbank = 0;

- if (!all_cpus) {
- /* Banks >64 can't be represented */
- if (bank >= 64)
- continue;
-
- /* Non-ex hypercalls can only address first 64 vCPUs */
- if (!ex && bank)
- continue;
+ /* Banks >64 can't be represented */
+ if (bank >= 64)
+ continue;

- if (ex) {
- /*
- * Check is the bank of this vCPU is in sparse
- * set and get the sparse bank number.
- */
- sbank = get_sparse_bank_no(valid_bank_mask,
- bank);
+ /* Non-ex hypercalls can only address first 64 vCPUs */
+ if (!ex && bank)
+ continue;

- if (sbank < 0)
- continue;
- }
+ if (ex) {
+ /*
+ * Check is the bank of this vCPU is in sparse
+ * set and get the sparse bank number.
+ */
+ sbank = get_sparse_bank_no(valid_bank_mask, bank);

- if (!(sparse_banks[sbank] & BIT_ULL(hv->vp_index % 64)))
+ if (sbank < 0)
continue;
}

+ if (!(sparse_banks[sbank] & BIT_ULL(hv->vp_index % 64)))
+ continue;
+
/*
* vcpu->arch.cr3 may not be up-to-date for running vCPUs so we
* can't analyze it here, flush TLB regardless of the specified
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ada21f47f22b..153f14e91fb1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -213,7 +213,7 @@ bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
me = get_cpu();

kvm_for_each_vcpu(i, vcpu, kvm) {
- if (!test_bit(i, vcpu_bitmap))
+ if (vcpu_bitmap && !test_bit(i, vcpu_bitmap))
continue;

kvm_make_request(req, vcpu);
@@ -237,12 +237,10 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
{
cpumask_var_t cpus;
bool called;
- static unsigned long vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)]
- = {[0 ... BITS_TO_LONGS(KVM_MAX_VCPUS)-1] = ULONG_MAX};

zalloc_cpumask_var(&cpus, GFP_ATOMIC);

- called = kvm_make_vcpus_request_mask(kvm, req, vcpu_bitmap, cpus);
+ called = kvm_make_vcpus_request_mask(kvm, req, NULL, cpus);

free_cpumask_var(cpus);
return called;
--
2.14.4