Re: [PATCH 1/4] KVM: x86: hyper-v: Drop redundant 'ex' parameter from kvm_hv_send_ipi()

Vitaly Kuznetsov
2022-02-28T10:02:53Z

Maxim Levitsky <mlevitsk@redhat.com> writes:

> On Tue, 2022-02-22 at 16:46 +0100, Vitaly Kuznetsov wrote:
>> 'struct kvm_hv_hcall' has all the required information already,
>> there's no need to pass 'ex' additionally.
>>
>> No functional change intended.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>> arch/x86/kvm/hyperv.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
>> index 6e38a7d22e97..15b6a7bd2346 100644
>> --- a/arch/x86/kvm/hyperv.c
>> +++ b/arch/x86/kvm/hyperv.c
>> @@ -1875,7 +1875,7 @@ static void kvm_send_ipi_to_many(struct kvm *kvm, u32 vector,
>> }
>> }
>>
>> -static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool ex)
>> +static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)
>> {
>> struct kvm *kvm = vcpu->kvm;
>> struct hv_send_ipi_ex send_ipi_ex;
>> @@ -1889,7 +1889,7 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool
>> u32 vector;
>> bool all_cpus;
>>
>> - if (!ex) {
>> + if (hc->code == HVCALL_SEND_IPI) {
>
> I am thinking, if we already touch this code,
> why not to use switch here instead on the hc->code,
> so that we can catch this function being called with something else than
> HVCALL_SEND_IPI_EX

I'm not against this second line of defense but kvm_hv_send_ipi() is
only called explicitly from kvm_hv_hypercall()'s switch so something is
really screwed up if we end up seeing something different from
HVCALL_SEND_IPI_EX/HVCALL_SEND_IPI here.

I'm now working on a bigger series for TLB flush improvements, will use
your suggestion there, thanks!

>
>> if (!hc->fast) {
>> if (unlikely(kvm_read_guest(kvm, hc->ingpa, &send_ipi,
>> sizeof(send_ipi))))
>> @@ -2279,14 +2279,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
>> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>> break;
>> }
>> - ret = kvm_hv_send_ipi(vcpu, &hc, false);
>> + ret = kvm_hv_send_ipi(vcpu, &hc);
>> break;
>> case HVCALL_SEND_IPI_EX:
>> if (unlikely(hc.fast || hc.rep)) {
>> ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
>> break;
>> }
>> - ret = kvm_hv_send_ipi(vcpu, &hc, true);
>> + ret = kvm_hv_send_ipi(vcpu, &hc);
>> break;
>> case HVCALL_POST_DEBUG_DATA:
>> case HVCALL_RETRIEVE_DEBUG_DATA:
>
>
>
> Other than this minor nitpick:
>
> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
>
>
> Best regards,
> Maxim Levitsky
>

--
Vitaly