Re: [RFC v7 7/7] KVM: arm: enable KVM_SIGNAL_MSI and MSI routing

["Radim Krčmář" <rkrcmar@redhat.com>]

2016-07-22 15:52+0200, Auger Eric:
> On 22/07/2016 15:39, Radim Krčmář wrote:
>> 2016-07-21 23:10+0200, Auger Eric:
>>> On 21/07/2016 18:33, Radim Krčmář wrote:
>>>> 2016-07-18 13:25+0000, Eric Auger:
>>>>> If the ITS modality is not available, let's simply support MSI
>>>>> injection by transforming the MSI.data into an SPI ID.
>>>>>
>>>>> This becomes possible to use KVM_SIGNAL_MSI ioctl and MSI
>>>>> routing for arm too.
>>>>>
>>>>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>>>>
>>>>> ---
>>>>> diff --git a/virt/kvm/arm/vgic/vgic-irqfd.c b/virt/kvm/arm/vgic/vgic-irqfd.c
>>>>> +static int vgic_v2m_inject_msi(struct kvm *kvm, struct kvm_msi *msi)
>>>>> +{
>>>>> +	if (msi->flags & KVM_MSI_VALID_DEVID)
>>>>> +		return -EINVAL;
>>>>> +	if (!vgic_valid_spi(kvm, msi->data))
>>>>> +		return -EINVAL;
>>>>> +
>>>>> +	return kvm_vgic_inject_irq(kvm, 0, msi->data, 1);
>>>>
>>>> Hm, this isn't very MSI related ...
>>>>
>>>> arm already has KVM_IRQ_LINE/kvm_vm_ioctl_irq_line with
>>>> KVM_ARM_IRQ_TYPE_SPI that does
>>>>   kvm_vgic_inject_irq(kvm, 0, irq_num, level)
>>>>
>>>> Is that interface lacking?
>>>
>>> You mean KVM_SIGNAL_MSI? Well at QEMU level, for ARM/ARM64 is doesn't.
>> 
>> No, I meant KVM_IRQ_LINE, the one that is used to deliver SPI today.
>> Or isn't it?
>> 
>>> For kvm-tools I guess, Andre manages without.
>>>
>>> My first feeling was it is part of the KVM API and we can implement it
>>> easily for GICv2M, as we do for GICv3 ITS . This can avoid a user app to
>>> do what QEMU implements as "kvm_gsi_direct_mapping" and manage the
>>> translation into the semantic of the ARM GSI.
>> 
>> I think that reusing KVM_SIGNAL_MSI and KVM_IRQ_ROUTING_MSI for SPI is
>> unfortunate.
>> 
>> SPI only uses msi.data, which makes remaining fields in the msi struct
>> arbitrary and [5/7] defined KVM_IRQ_ROUTING_IRQCHIP for SPI, so two
>> route types now do the same, but only sometimes (without ITS), which
>> makes the situation even less understandable ...
>> 
>> Delivering SPI as KVM_IRQ_ROUTING_IRQCHIP seems more sensible and if we
>> wanted ad-hoc delivery of KVM_IRQ_ROUTING_IRQCHIP, then I would prefer a
>> new interface to two different meanings for KVM_SIGNAL_MSI:
>> KVM_SIGNAL_MSI was created because we didn't have anything that could
>> inject an interrupt without setting up a route with KVM_SET_GSI_ROUTING
>> and we are still missing a generic interface to do that.
>> 
>>> But Well, if you prefer we do not implement it for GICv2M, since
>>> considered as far fetched I can remove this patch.
>> 
>> I do, thanks.  Documentation in [6/7] was ahead and needs changing then.
> 
> Argh just saw your reply after sending v8. Will respin immediatly.
> 
> Sorry for the confusion

No problem.  Give me half an hour for a review, please. :)