From: Shenming Lu <lushenming@huawei.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Eric Auger <eric.auger@redhat.com>, Will Deacon <will@kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<kvmarm@lists.cs.columbia.edu>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
Alex Williamson <alex.williamson@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
<wanghaibin.wang@huawei.com>, <yuzenghui@huawei.com>
Subject: Re: [RFC PATCH v2 3/4] KVM: arm64: GICv4.1: Restore VLPI's pending state to physical side
Date: Wed, 6 Jan 2021 10:12:50 +0800 [thread overview]
Message-ID: <6b815f0e-d042-2ec6-369a-41a19cd1b9f9@huawei.com> (raw)
In-Reply-To: <76a7b9cca485dc8157d3be53189eac69@kernel.org>
On 2021/1/5 17:25, Marc Zyngier wrote:
> On 2021-01-04 08:16, Shenming Lu wrote:
>> From: Zenghui Yu <yuzenghui@huawei.com>
>>
>> When setting the forwarding path of a VLPI (switch to the HW mode),
>> we could also transfer the pending state from irq->pending_latch to
>> VPT (especially in migration, the pending states of VLPIs are restored
>> into kvm’s vgic first). And we currently send "INT+VSYNC" to trigger
>> a VLPI to pending.
>>
>> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
>> Signed-off-by: Shenming Lu <lushenming@huawei.com>
>> ---
>> arch/arm64/kvm/vgic/vgic-v4.c | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
>> index f211a7c32704..7945d6d09cdd 100644
>> --- a/arch/arm64/kvm/vgic/vgic-v4.c
>> +++ b/arch/arm64/kvm/vgic/vgic-v4.c
>> @@ -454,6 +454,18 @@ int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int virq,
>> irq->host_irq = virq;
>> atomic_inc(&map.vpe->vlpi_count);
>>
>> + /* Transfer pending state */
>> + ret = irq_set_irqchip_state(irq->host_irq,
>> + IRQCHIP_STATE_PENDING,
>> + irq->pending_latch);
>> + WARN_RATELIMIT(ret, "IRQ %d", irq->host_irq);
>
> Why do this if pending_latch is 0, which is likely to be
> the overwhelming case?
Yes, there is no need to do this if pending_latch is 0.
>
>> +
>> + /*
>> + * Let it be pruned from ap_list later and don't bother
>> + * the List Register.
>> + */
>> + irq->pending_latch = false;
>
> What guarantees the pruning? Pruning only happens on vcpu exit,
> which means we may have the same interrupt via both the LR and
> the stream interface, which I don't believe is legal (it is
> like having two LRs holding the same interrupt).
Since the irq's pending_latch is set to false here, it will not be
populated to the LR in vgic_flush_lr_state() (vgic_target_oracle()
will return NULL).
>
>> +
>> out:
>> mutex_unlock(&its->its_lock);
>> return ret;
>
> Thanks,
>
> M.
next prev parent reply other threads:[~2021-01-06 2:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-04 8:16 [RFC PATCH v2 0/4] KVM: arm64: Add VLPI migration support on GICv4.1 Shenming Lu
2021-01-04 8:16 ` [RFC PATCH v2 1/4] KVM: arm64: GICv4.1: Add function to get VLPI state Shenming Lu
2021-01-04 8:16 ` [RFC PATCH v2 2/4] KVM: arm64: GICv4.1: Try to save hw pending state in save_pending_tables Shenming Lu
2021-01-05 9:13 ` Marc Zyngier
2021-01-05 11:40 ` Marc Zyngier
2021-01-06 5:48 ` Shenming Lu
2021-01-05 13:02 ` Shenming Lu
2021-01-05 13:47 ` Marc Zyngier
2021-01-06 7:14 ` Shenming Lu
2021-01-04 8:16 ` [RFC PATCH v2 3/4] KVM: arm64: GICv4.1: Restore VLPI's pending state to physical side Shenming Lu
2021-01-05 9:25 ` Marc Zyngier
2021-01-06 2:12 ` Shenming Lu [this message]
2021-01-04 8:16 ` [RFC PATCH v2 4/4] KVM: arm64: GICv4.1: Give a chance to save VLPI's pending state Shenming Lu
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