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Subject[PATCH v6 6/7] KVM: x86: hyperv: optimize kvm_hv_flush_tlb() for vp_index == vcpu_idx case
Date
VP inedx almost always matches VCPU and when it does it's faster to walk
the sparse set instead of all vcpus.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/hyperv.c | 96 +++++++++++++++++++++++--------------------
1 file changed, 52 insertions(+), 44 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index eeb12eacd525..cc0535a078f7 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1277,32 +1277,37 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
return kvm_hv_get_msr(vcpu, msr, pdata, host);
}

-static __always_inline int get_sparse_bank_no(u64 valid_bank_mask, int bank_no)
+static __always_inline bool hv_vcpu_in_sparse_set(struct kvm_vcpu_hv *hv_vcpu,
+ u64 sparse_banks[],
+ u64 valid_bank_mask)
{
- int i = 0, j;
+ int bank = hv_vcpu->vp_index / 64, sbank;

- if (!(valid_bank_mask & BIT_ULL(bank_no)))
- return -1;
+ if (bank >= 64)
+ return false;

- for (j = 0; j < bank_no; j++)
- if (valid_bank_mask & BIT_ULL(j))
- i++;
+ if (!(valid_bank_mask & BIT_ULL(bank)))
+ return false;

- return i;
+ /* Sparse bank number equals to the number of set bits before it */
+ sbank = bitmap_weight((unsigned long *)&valid_bank_mask, bank);
+
+ return !!(sparse_banks[sbank] & BIT_ULL(hv_vcpu->vp_index % 64));
}

static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
u16 rep_cnt, bool ex)
{
struct kvm *kvm = current_vcpu->kvm;
- struct kvm_vcpu_hv *hv_current = &current_vcpu->arch.hyperv;
+ struct kvm_hv *hv = &kvm->arch.hyperv;
+ struct kvm_vcpu_hv *hv_vcpu = &current_vcpu->arch.hyperv;
struct hv_tlb_flush_ex flush_ex;
struct hv_tlb_flush flush;
struct kvm_vcpu *vcpu;
unsigned long vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)] = {0};
- u64 valid_bank_mask = 0;
+ u64 valid_bank_mask;
u64 sparse_banks[64];
- int sparse_banks_len, i;
+ int sparse_banks_len, i, bank, sbank;
bool all_cpus;

if (!ex) {
@@ -1312,6 +1317,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
trace_kvm_hv_flush_tlb(flush.processor_mask,
flush.address_space, flush.flags);

+ valid_bank_mask = BIT_ULL(0);
sparse_banks[0] = flush.processor_mask;
all_cpus = flush.flags & HV_FLUSH_ALL_PROCESSORS;
} else {
@@ -1344,52 +1350,54 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
return HV_STATUS_INVALID_HYPERCALL_INPUT;
}

- cpumask_clear(&hv_current->tlb_lush);
+ /*
+ * 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 address space.
+ */
+ cpumask_clear(&hv_vcpu->tlb_lush);

if (all_cpus) {
kvm_make_vcpus_request_mask(kvm,
KVM_REQ_TLB_FLUSH | KVM_REQUEST_NO_WAKEUP,
- NULL, &hv_current->tlb_lush);
+ NULL, &hv_vcpu->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;
-
- /* Banks >64 can't be represented */
- if (bank >= 64)
- continue;
-
- /* Non-ex hypercalls can only address first 64 vCPUs */
- if (!ex && bank)
- 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 (sbank < 0)
- continue;
+ if (atomic_read(&hv->num_mismatched_vp_indexes)) {
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (hv_vcpu_in_sparse_set(&vcpu->arch.hyperv,
+ sparse_banks,
+ valid_bank_mask))
+ __set_bit(i, vcpu_bitmap);
}
+ goto flush_request;
+ }

- 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
- * address space.
- */
- __set_bit(i, vcpu_bitmap);
+ /*
+ * num_mismatched_vp_indexes is zero so every vcpu has
+ * vp_index == vcpu_idx.
+ */
+ sbank = 0;
+ for_each_set_bit(bank, (unsigned long *)&valid_bank_mask,
+ BITS_PER_LONG) {
+ for_each_set_bit(i,
+ (unsigned long *)&sparse_banks[sbank],
+ BITS_PER_LONG) {
+ u32 vp_index = bank * 64 + i;
+
+ /* A non-existent vCPU was specified */
+ if (vp_index >= KVM_MAX_VCPUS)
+ return HV_STATUS_INVALID_HYPERCALL_INPUT;
+
+ __set_bit(vp_index, vcpu_bitmap);
+ }
+ sbank++;
}

+flush_request:
kvm_make_vcpus_request_mask(kvm,
KVM_REQ_TLB_FLUSH | KVM_REQUEST_NO_WAKEUP,
- vcpu_bitmap, &hv_current->tlb_lush);
+ vcpu_bitmap, &hv_vcpu->tlb_lush);

ret_success:
/* We always do full TLB flush, set rep_done = rep_cnt. */
--
2.17.1
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