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Date: Mon, 30 Nov 2020 20:12:35 +0800
From: Shenming Lu <lushenming@...wei.com>
To: Marc Zyngier <maz@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>,
<linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>,
James Morse <james.morse@....com>,
Julien Thierry <julien.thierry.kdev@...il.com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Eric Auger <eric.auger@...hat.com>,
Christoffer Dall <christoffer.dall@....com>,
<wanghaibin.wang@...wei.com>, <yuzenghui@...wei.com>
Subject: Re: [PATCH v2 2/2] KVM: arm64: Delay the execution of the polling on
the GICR_VPENDBASER.Dirty bit
On 2020/11/30 19:22, Marc Zyngier wrote:
> On 2020-11-28 14:18, Shenming Lu wrote:
>> In order to further reduce the impact of the wait delay of the
>> VPT analysis, we can delay the execution of the polling on the
>> GICR_VPENDBASER.Dirty bit (call it from kvm_vgic_flush_hwstate()
>> corresponding to vPE resident), let the GIC and the CPU work in
>> parallel on the entry path.
>>
>> Signed-off-by: Shenming Lu <lushenming@...wei.com>
>> ---
>> arch/arm64/kvm/vgic/vgic-v4.c | 16 ++++++++++++++++
>> arch/arm64/kvm/vgic/vgic.c | 3 +++
>> drivers/irqchip/irq-gic-v3-its.c | 16 ++++++++++++----
>> drivers/irqchip/irq-gic-v4.c | 11 +++++++++++
>> include/kvm/arm_vgic.h | 3 +++
>> include/linux/irqchip/arm-gic-v4.h | 4 ++++
>> 6 files changed, 49 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
>> index b5fa73c9fd35..b0da74809187 100644
>> --- a/arch/arm64/kvm/vgic/vgic-v4.c
>> +++ b/arch/arm64/kvm/vgic/vgic-v4.c
>> @@ -353,6 +353,22 @@ int vgic_v4_load(struct kvm_vcpu *vcpu)
>> return err;
>> }
>>
>> +void vgic_v4_commit(struct kvm_vcpu *vcpu)
>> +{
>> + struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
>> +
>> + /*
>> + * No need to wait for the vPE to be ready across a shallow guest
>> + * exit, as only a vcpu_put will invalidate it.
>> + */
>> + if (vpe->vpe_ready)
>> + return;
>> +
>> + its_commit_vpe(vpe);
>> +
>> + vpe->vpe_ready = true;
>
> This should be written as:
>
> if (!ready)
> commit();
>
> and ready being driven by the commit() call itself.
>
>> +}
>> +
>> static struct vgic_its *vgic_get_its(struct kvm *kvm,
>> struct kvm_kernel_irq_routing_entry *irq_entry)
>> {
>> diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c
>> index c3643b7f101b..1c597c9885fa 100644
>> --- a/arch/arm64/kvm/vgic/vgic.c
>> +++ b/arch/arm64/kvm/vgic/vgic.c
>> @@ -915,6 +915,9 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
>>
>> if (can_access_vgic_from_kernel())
>> vgic_restore_state(vcpu);
>> +
>> + if (vgic_supports_direct_msis(vcpu->kvm))
>> + vgic_v4_commit(vcpu);
>> }
>>
>> void kvm_vgic_load(struct kvm_vcpu *vcpu)
>> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
>> index 22f427135c6b..f30aba14933e 100644
>> --- a/drivers/irqchip/irq-gic-v3-its.c
>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>> @@ -3842,8 +3842,6 @@ static void its_vpe_schedule(struct its_vpe *vpe)
>> val |= vpe->idai ? GICR_VPENDBASER_IDAI : 0;
>> val |= GICR_VPENDBASER_Valid;
>> gicr_write_vpendbaser(val, vlpi_base + GICR_VPENDBASER);
>> -
>> - its_wait_vpt_parse_complete();
>> }
>>
>> static void its_vpe_deschedule(struct its_vpe *vpe)
>> @@ -3855,6 +3853,8 @@ static void its_vpe_deschedule(struct its_vpe *vpe)
>>
>> vpe->idai = !!(val & GICR_VPENDBASER_IDAI);
>> vpe->pending_last = !!(val & GICR_VPENDBASER_PendingLast);
>> +
>> + vpe->vpe_ready = false;
>
> This should be set from the its_make_vpe_non_resident() call.
>
>> }
>>
>> static void its_vpe_invall(struct its_vpe *vpe)
>> @@ -3891,6 +3891,10 @@ static int its_vpe_set_vcpu_affinity(struct
>> irq_data *d, void *vcpu_info)
>> its_vpe_deschedule(vpe);
>> return 0;
>>
>> + case COMMIT_VPE:
>> + its_wait_vpt_parse_complete();
>> + return 0;
>> +
>> case INVALL_VPE:
>> its_vpe_invall(vpe);
>> return 0;
>> @@ -4052,8 +4056,6 @@ static void its_vpe_4_1_schedule(struct its_vpe *vpe,
>> val |= FIELD_PREP(GICR_VPENDBASER_4_1_VPEID, vpe->vpe_id);
>>
>> gicr_write_vpendbaser(val, vlpi_base + GICR_VPENDBASER);
>> -
>> - its_wait_vpt_parse_complete();
>> }
>>
>> static void its_vpe_4_1_deschedule(struct its_vpe *vpe,
>> @@ -4091,6 +4093,8 @@ static void its_vpe_4_1_deschedule(struct its_vpe *vpe,
>> GICR_VPENDBASER_PendingLast);
>> vpe->pending_last = true;
>> }
>> +
>> + vpe->vpe_ready = false;
>> }
>>
>> static void its_vpe_4_1_invall(struct its_vpe *vpe)
>> @@ -4128,6 +4132,10 @@ static int its_vpe_4_1_set_vcpu_affinity(struct
>> irq_data *d, void *vcpu_info)
>> its_vpe_4_1_deschedule(vpe, info);
>> return 0;
>>
>> + case COMMIT_VPE:
>> + its_wait_vpt_parse_complete();
>> + return 0;
>> +
>> case INVALL_VPE:
>> its_vpe_4_1_invall(vpe);
>> return 0;
>> diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c
>> index 0c18714ae13e..6cea71a4e68b 100644
>> --- a/drivers/irqchip/irq-gic-v4.c
>> +++ b/drivers/irqchip/irq-gic-v4.c
>> @@ -258,6 +258,17 @@ int its_make_vpe_resident(struct its_vpe *vpe,
>> bool g0en, bool g1en)
>> return ret;
>> }
>>
>> +int its_commit_vpe(struct its_vpe *vpe)
>> +{
>> + struct its_cmd_info info = {
>> + .cmd_type = COMMIT_VPE,
>> + };
>> +
>> + WARN_ON(preemptible());
>> +
>> + return its_send_vpe_cmd(vpe, &info);
>> +}
>> +
>> int its_invall_vpe(struct its_vpe *vpe)
>> {
>> struct its_cmd_info info = {
>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
>> index a8d8fdcd3723..f2170df6cf7c 100644
>> --- a/include/kvm/arm_vgic.h
>> +++ b/include/kvm/arm_vgic.h
>> @@ -401,7 +401,10 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int irq,
>> int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq,
>> struct kvm_kernel_irq_routing_entry *irq_entry);
>>
>> +void vgic_v4_commit(struct kvm_vcpu *vcpu);
>> +
>> int vgic_v4_load(struct kvm_vcpu *vcpu);
>> +
>
> Spurious new lines.
>
>> int vgic_v4_put(struct kvm_vcpu *vcpu, bool need_db);
>>
>> #endif /* __KVM_ARM_VGIC_H */
>> diff --git a/include/linux/irqchip/arm-gic-v4.h
>> b/include/linux/irqchip/arm-gic-v4.h
>> index 6976b8331b60..936d88e482a9 100644
>> --- a/include/linux/irqchip/arm-gic-v4.h
>> +++ b/include/linux/irqchip/arm-gic-v4.h
>> @@ -75,6 +75,8 @@ struct its_vpe {
>> u16 vpe_id;
>> /* Pending VLPIs on schedule out? */
>> bool pending_last;
>> + /* VPT parse complete */
>> + bool vpe_ready;
>> };
>>
>> /*
>> @@ -104,6 +106,7 @@ enum its_vcpu_info_cmd_type {
>> PROP_UPDATE_AND_INV_VLPI,
>> SCHEDULE_VPE,
>> DESCHEDULE_VPE,
>> + COMMIT_VPE,
>> INVALL_VPE,
>> PROP_UPDATE_VSGI,
>> };
>> @@ -129,6 +132,7 @@ int its_alloc_vcpu_irqs(struct its_vm *vm);
>> void its_free_vcpu_irqs(struct its_vm *vm);
>> int its_make_vpe_resident(struct its_vpe *vpe, bool g0en, bool g1en);
>> int its_make_vpe_non_resident(struct its_vpe *vpe, bool db);
>> +int its_commit_vpe(struct its_vpe *vpe);
>> int its_invall_vpe(struct its_vpe *vpe);
>> int its_map_vlpi(int irq, struct its_vlpi_map *map);
>> int its_get_vlpi(int irq, struct its_vlpi_map *map);
>
> In order to speed up the respin round-trip, I've taken the liberty
> to refactor this patch myself. Please have a look at [1] and let
> me know if you're OK with it.
I have looked at it and am OK.
By the way, will the first patch (set the delay_us to 1) be picked up
together?
Thanks,
Shenming
>
> Thanks,
>
> M.
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/misc-5.11&id=57e3cebd022fbc035dcf190ac789fd2ffc747f5b
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