Re: [PATCH] x86/hyper-v: Stop caring about EOI for direct stimers

Vitaly Kuznetsov
2018-12-12T13:09:18Z

Roman Kagan <rkagan@virtuozzo.com> writes:

> [ Sorry, missed this one ]
>
> On Wed, Dec 05, 2018 at 04:36:21PM +0100, Vitaly Kuznetsov wrote:
>> Turns out we over-engineered Direct Mode for stimers a bit: unlike
>> traditional stimers where we may want to try to re-inject the message upon
>> EOI, Direct Mode stimers just set the irq in APIC and kvm_apic_set_irq()
>> fails only when APIC is disabled (see APIC_DM_FIXED case in
>> __apic_accept_irq()). Remove the redundant part.
>>
>> Suggested-by: Roman Kagan <rkagan@virtuozzo.com>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>> arch/x86/kvm/hyperv.c | 36 +++---------------------------------
>> 1 file changed, 3 insertions(+), 33 deletions(-)
>>
>> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
>> index e6a2a085644a..0a16a77e6ac3 100644
>> --- a/arch/x86/kvm/hyperv.c
>> +++ b/arch/x86/kvm/hyperv.c
>> @@ -56,21 +56,8 @@ static inline int synic_get_sint_vector(u64 sint_value)
>> static bool synic_has_vector_connected(struct kvm_vcpu_hv_synic *synic,
>> int vector)
>> {
>> - struct kvm_vcpu *vcpu = synic_to_vcpu(synic);
>> - struct kvm_vcpu_hv *hv_vcpu = vcpu_to_hv_vcpu(vcpu);
>> - struct kvm_vcpu_hv_stimer *stimer;
>> int i;
>>
>> - for (i = 0; i < ARRAY_SIZE(hv_vcpu->stimer); i++) {
>> - stimer = &hv_vcpu->stimer[i];
>> - if (stimer->config.enable && stimer->config.direct_mode &&
>> - stimer->config.apic_vector == vector)
>> - return true;
>> - }
>> -
>> - if (vector < HV_SYNIC_FIRST_VALID_VECTOR)
>> - return false;
>> -
>> for (i = 0; i < ARRAY_SIZE(synic->sint); i++) {
>> if (synic_get_sint_vector(synic_read_sint(synic, i)) == vector)
>> return true;
>> @@ -96,14 +83,14 @@ static bool synic_has_vector_auto_eoi(struct kvm_vcpu_hv_synic *synic,
>> static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
>> int vector)
>> {
>> + if (vector < HV_SYNIC_FIRST_VALID_VECTOR)
>> + return;
>> +
>> if (synic_has_vector_connected(synic, vector))
>> __set_bit(vector, synic->vec_bitmap);
>> else
>> __clear_bit(vector, synic->vec_bitmap);
>>
>> - if (vector < HV_SYNIC_FIRST_VALID_VECTOR)
>> - return;
>> -
>> if (synic_has_vector_auto_eoi(synic, vector))
>> __set_bit(vector, synic->auto_eoi_bitmap);
>> else
>> @@ -382,9 +369,7 @@ int kvm_hv_synic_set_irq(struct kvm *kvm, u32 vpidx, u32 sint)
>>
>> void kvm_hv_synic_send_eoi(struct kvm_vcpu *vcpu, int vector)
>> {
>> - struct kvm_vcpu_hv *hv_vcpu = vcpu_to_hv_vcpu(vcpu);
>> struct kvm_vcpu_hv_synic *synic = vcpu_to_synic(vcpu);
>> - struct kvm_vcpu_hv_stimer *stimer;
>> int i;
>>
>> trace_kvm_hv_synic_send_eoi(vcpu->vcpu_id, vector);
>> @@ -392,14 +377,6 @@ void kvm_hv_synic_send_eoi(struct kvm_vcpu *vcpu, int vector)
>> for (i = 0; i < ARRAY_SIZE(synic->sint); i++)
>> if (synic_get_sint_vector(synic_read_sint(synic, i)) == vector)
>> kvm_hv_notify_acked_sint(vcpu, i);
>> -
>> - for (i = 0; i < ARRAY_SIZE(hv_vcpu->stimer); i++) {
>> - stimer = &hv_vcpu->stimer[i];
>> - if (stimer->msg_pending && stimer->config.enable &&
>> - stimer->config.direct_mode &&
>> - stimer->config.apic_vector == vector)
>> - stimer_mark_pending(stimer, false);
>> - }
>> }
>>
>> static int kvm_hv_set_sint_gsi(struct kvm *kvm, u32 vpidx, u32 sint, int gsi)
>> @@ -566,8 +543,6 @@ static int stimer_start(struct kvm_vcpu_hv_stimer *stimer)
>> static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,
>> bool host)
>> {
>> - struct kvm_vcpu *vcpu = stimer_to_vcpu(stimer);
>> - struct kvm_vcpu_hv *hv_vcpu = vcpu_to_hv_vcpu(vcpu);
>> union hv_stimer_config new_config = {.as_uint64 = config},
>> old_config = {.as_uint64 = stimer->config.as_uint64};
>>
>> @@ -580,11 +555,6 @@ static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,
>> new_config.enable = 0;
>> stimer->config.as_uint64 = new_config.as_uint64;
>>
>> - if (old_config.direct_mode)
>> - synic_update_vector(&hv_vcpu->synic, old_config.apic_vector);
>> - if (new_config.direct_mode)
>> - synic_update_vector(&hv_vcpu->synic, new_config.apic_vector);
>> -
>> stimer_mark_pending(stimer, false);
>> return 0;
>> }
>
> As discussed in another thread, it seems worth while to make
> stimer_set_config reject vectors 0..15.
>
> Besides I'd rather sqwash this patch into the one that introduced direct
> timers, before it reached Linus' tree.

I'm fine either way, I'm going to send v2 with a new patch adding the
check to stimer_set_config() and leave it up to Paolo if he would want
to squash them all together before sending to Linus.

(Actually I don't see direct stimers in kvm/queue but I think I heard
'queued' from Paolo...)

--
Vitaly