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    Subject[PATCH v5 05/37] KVM: x86: hyper-v: Handle HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls gently
    Date
    Currently, HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST{,EX} calls are handled
    the exact same way as HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE{,EX}: by
    flushing the whole VPID and this is sub-optimal. Switch to handling
    these requests with 'flush_tlb_gva()' hooks instead. Use the newly
    introduced TLB flush fifo to queue the requests.

    Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
    ---
    arch/x86/kvm/hyperv.c | 100 +++++++++++++++++++++++++++++++++++++-----
    1 file changed, 88 insertions(+), 12 deletions(-)

    diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
    index 762b0b699fdf..956072592e2f 100644
    --- a/arch/x86/kvm/hyperv.c
    +++ b/arch/x86/kvm/hyperv.c
    @@ -1806,32 +1806,82 @@ static u64 kvm_get_sparse_vp_set(struct kvm *kvm, struct kvm_hv_hcall *hc,
    sparse_banks, consumed_xmm_halves, offset);
    }

    -static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu)
    +static int kvm_hv_get_tlb_flush_entries(struct kvm *kvm, struct kvm_hv_hcall *hc, u64 entries[],
    + int consumed_xmm_halves, gpa_t offset)
    +{
    + return kvm_hv_get_hc_data(kvm, hc, hc->rep_cnt, hc->rep_cnt,
    + entries, consumed_xmm_halves, offset);
    +}
    +
    +static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu, u64 *entries, int count)
    {
    struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
    struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
    u64 entry = KVM_HV_TLB_FLUSHALL_ENTRY;
    + unsigned long flags;

    if (!hv_vcpu)
    return;

    tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo;

    - kfifo_in_spinlocked(&tlb_flush_fifo->entries, &entry, 1, &tlb_flush_fifo->write_lock);
    + spin_lock_irqsave(&tlb_flush_fifo->write_lock, flags);
    +
    + /*
    + * All entries should fit on the fifo leaving one free for 'flush all'
    + * entry in case another request comes in. In case there's not enough
    + * space, just put 'flush all' entry there.
    + */
    + if (count && entries && count < kfifo_avail(&tlb_flush_fifo->entries)) {
    + WARN_ON(kfifo_in(&tlb_flush_fifo->entries, entries, count) != count);
    + goto out_unlock;
    + }
    +
    + /*
    + * Note: full fifo always contains 'flush all' entry, no need to check the
    + * return value.
    + */
    + kfifo_in(&tlb_flush_fifo->entries, &entry, 1);
    +
    +out_unlock:
    + spin_unlock_irqrestore(&tlb_flush_fifo->write_lock, flags);
    }

    void kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
    {
    struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
    struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
    + u64 entries[KVM_HV_TLB_FLUSH_FIFO_SIZE];
    + int i, j, count;
    + gva_t gva;

    - kvm_vcpu_flush_tlb_guest(vcpu);
    -
    - if (!hv_vcpu)
    + if (!tdp_enabled || !hv_vcpu) {
    + kvm_vcpu_flush_tlb_guest(vcpu);
    return;
    + }

    tlb_flush_fifo = &hv_vcpu->tlb_flush_fifo;

    + count = kfifo_out(&tlb_flush_fifo->entries, entries, KVM_HV_TLB_FLUSH_FIFO_SIZE);
    +
    + for (i = 0; i < count; i++) {
    + if (entries[i] == KVM_HV_TLB_FLUSHALL_ENTRY)
    + goto out_flush_all;
    +
    + /*
    + * Lower 12 bits of 'address' encode the number of additional
    + * pages to flush.
    + */
    + gva = entries[i] & PAGE_MASK;
    + for (j = 0; j < (entries[i] & ~PAGE_MASK) + 1; j++)
    + static_call(kvm_x86_flush_tlb_gva)(vcpu, gva + j * PAGE_SIZE);
    +
    + ++vcpu->stat.tlb_flush;
    + }
    + return;
    +
    +out_flush_all:
    + kvm_vcpu_flush_tlb_guest(vcpu);
    kfifo_reset_out(&tlb_flush_fifo->entries);
    }

    @@ -1841,11 +1891,21 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
    struct hv_tlb_flush_ex flush_ex;
    struct hv_tlb_flush flush;
    DECLARE_BITMAP(vcpu_mask, KVM_MAX_VCPUS);
    + /*
    + * Normally, there can be no more than 'KVM_HV_TLB_FLUSH_FIFO_SIZE'
    + * entries on the TLB flush fifo. The last entry, however, needs to be
    + * always left free for 'flush all' entry which gets placed when
    + * there is not enough space to put all the requested entries.
    + */
    + u64 __tlb_flush_entries[KVM_HV_TLB_FLUSH_FIFO_SIZE - 1];
    + u64 *tlb_flush_entries;
    u64 valid_bank_mask;
    u64 sparse_banks[KVM_HV_MAX_SPARSE_VCPU_SET_BITS];
    struct kvm_vcpu *v;
    unsigned long i;
    bool all_cpus;
    + int consumed_xmm_halves = 0;
    + gpa_t data_offset;

    /*
    * The Hyper-V TLFS doesn't allow more than 64 sparse banks, e.g. the
    @@ -1861,10 +1921,12 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
    flush.address_space = hc->ingpa;
    flush.flags = hc->outgpa;
    flush.processor_mask = sse128_lo(hc->xmm[0]);
    + consumed_xmm_halves = 1;
    } else {
    if (unlikely(kvm_read_guest(kvm, hc->ingpa,
    &flush, sizeof(flush))))
    return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + data_offset = sizeof(flush);
    }

    trace_kvm_hv_flush_tlb(flush.processor_mask,
    @@ -1888,10 +1950,12 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
    flush_ex.flags = hc->outgpa;
    memcpy(&flush_ex.hv_vp_set,
    &hc->xmm[0], sizeof(hc->xmm[0]));
    + consumed_xmm_halves = 2;
    } else {
    if (unlikely(kvm_read_guest(kvm, hc->ingpa, &flush_ex,
    sizeof(flush_ex))))
    return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + data_offset = sizeof(flush_ex);
    }

    trace_kvm_hv_flush_tlb_ex(flush_ex.hv_vp_set.valid_bank_mask,
    @@ -1907,25 +1971,37 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
    return HV_STATUS_INVALID_HYPERCALL_INPUT;

    if (all_cpus)
    - goto do_flush;
    + goto read_flush_entries;

    if (!hc->var_cnt)
    goto ret_success;

    - if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks, 2,
    - offsetof(struct hv_tlb_flush_ex,
    - hv_vp_set.bank_contents)))
    + if (kvm_get_sparse_vp_set(kvm, hc, sparse_banks, consumed_xmm_halves,
    + data_offset))
    + return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + data_offset += hc->var_cnt * sizeof(sparse_banks[0]);
    + consumed_xmm_halves += hc->var_cnt;
    + }
    +
    +read_flush_entries:
    + if (hc->code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE ||
    + hc->code == HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX ||
    + hc->rep_cnt > ARRAY_SIZE(__tlb_flush_entries)) {
    + tlb_flush_entries = NULL;
    + } else {
    + if (kvm_hv_get_tlb_flush_entries(kvm, hc, __tlb_flush_entries,
    + consumed_xmm_halves, data_offset))
    return HV_STATUS_INVALID_HYPERCALL_INPUT;
    + tlb_flush_entries = __tlb_flush_entries;
    }

    -do_flush:
    /*
    * 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.
    */
    if (all_cpus) {
    kvm_for_each_vcpu(i, v, kvm)
    - hv_tlb_flush_enqueue(v);
    + hv_tlb_flush_enqueue(v, tlb_flush_entries, hc->rep_cnt);

    kvm_make_all_cpus_request(kvm, KVM_REQ_HV_TLB_FLUSH);
    } else {
    @@ -1935,7 +2011,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
    v = kvm_get_vcpu(kvm, i);
    if (!v)
    continue;
    - hv_tlb_flush_enqueue(v);
    + hv_tlb_flush_enqueue(v, tlb_flush_entries, hc->rep_cnt);
    }

    kvm_make_vcpus_request_mask(kvm, KVM_REQ_HV_TLB_FLUSH, vcpu_mask);
    --
    2.35.3
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