Re: [PATCH v2 3/8] KVM: x86: Refactor kvm_hv_flush_tlb() to reduce indentation

Vitaly Kuznetsov
2021-11-01T10:01:10Z

Sean Christopherson <seanjc@google.com> writes:

> Refactor the "extended" path of kvm_hv_flush_tlb() to reduce the nesting
> depth for the non-fast sparse path, and to make the code more similar to
> the extended path in kvm_hv_send_ipi().
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/hyperv.c | 40 +++++++++++++++++++++-------------------
> 1 file changed, 21 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index cf18aa1712bf..e68931ed27f6 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1814,31 +1814,33 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
> if (hc->var_cnt != bitmap_weight((unsigned long *)&valid_bank_mask, 64))
> return HV_STATUS_INVALID_HYPERCALL_INPUT;
>
> - if (!hc->var_cnt && !all_cpus)
> + if (all_cpus)
> + goto do_flush;

You could've probably done:

if (all_cpus) {
kvm_make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH_GUEST);
goto ret_success;
}

to get rid on the second 'all_cpus' check (and maybe even 'do_flush'
label with some extra work) below.

> +
> + if (!hc->var_cnt)
> goto ret_success;
>
> - if (!all_cpus) {
> - if (hc->fast) {
> - if (hc->var_cnt > HV_HYPERCALL_MAX_XMM_REGISTERS - 1)
> - return HV_STATUS_INVALID_HYPERCALL_INPUT;
> - for (i = 0; i < hc->var_cnt; i += 2) {
> - sparse_banks[i] = sse128_lo(hc->xmm[i / 2 + 1]);
> - sparse_banks[i + 1] = sse128_hi(hc->xmm[i / 2 + 1]);
> - }
> - } else {
> - if (hc->var_cnt > 64)
> - return HV_STATUS_INVALID_HYPERCALL_INPUT;
> -
> - gpa = hc->ingpa + offsetof(struct hv_tlb_flush_ex,
> - hv_vp_set.bank_contents);
> - if (unlikely(kvm_read_guest(kvm, gpa, sparse_banks,
> - hc->var_cnt *
> - sizeof(sparse_banks[0]))))
> - return HV_STATUS_INVALID_HYPERCALL_INPUT;
> + if (hc->fast) {
> + if (hc->var_cnt > HV_HYPERCALL_MAX_XMM_REGISTERS - 1)
> + return HV_STATUS_INVALID_HYPERCALL_INPUT;
> + for (i = 0; i < hc->var_cnt; i += 2) {
> + sparse_banks[i] = sse128_lo(hc->xmm[i / 2 + 1]);
> + sparse_banks[i + 1] = sse128_hi(hc->xmm[i / 2 + 1]);
> }
> + goto do_flush;
> }
> +
> + if (hc->var_cnt > 64)
> + return HV_STATUS_INVALID_HYPERCALL_INPUT;
> +
> + gpa = hc->ingpa + offsetof(struct hv_tlb_flush_ex,
> + hv_vp_set.bank_contents);
> + if (unlikely(kvm_read_guest(kvm, gpa, sparse_banks,
> + hc->var_cnt * sizeof(sparse_banks[0]))))
> + return HV_STATUS_INVALID_HYPERCALL_INPUT;
> }
>
> +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.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly