On 7 October 2020 13:59:00 BST, Thomas Gleixner <t...@linutronix.de> wrote:
>On Wed, Oct 07 2020 at 08:48, David Woodhouse wrote:
>> On Tue, 2020-10-06 at 23:54 +0200, Thomas Gleixner wrote:
>>> On Mon, Oct 05 2020 at 16:28, David Woodhouse wrote:
>> This is the case I called out in the cover letter:
>>
>> This patch series implements a per-domain "maximum affinity" set
>and
>> uses it for the non-remapped IOAPIC and MSI domains on x86. As
>well as
>> allowing more CPUs to be used without interrupt remapping, this
>also
>> fixes the case where some IOAPICs or PCI devices aren't actually
>in
>> scope of any active IOMMU and are operating without remapping.
>>
>> To fix *that* case, we really do need the whole series giving us per-
>> domain restricted affinity, and to use it for those MSIs/IOAPICs that
>> the IRQ remapping doesn't cover.
>
>Which do not exist today.
Sure. But at patch 10/13 into this particular patch series, it *does* exist.
(Ignoring, for the moment, that I'm about to rewrite half the preceding patches
to take a different approach)
>>> > ip->irqdomain->parent = parent;
>>> > + if (parent == x86_vector_domain)
>>> > + irq_domain_set_affinity(ip->irqdomain, &x86_non_ir_cpumask);
>>>
>>> OMG
>>
>> This IOAPIC function may or may not be behind remapping.
>
>>> > d->flags |= IRQ_DOMAIN_MSI_NOMASK_QUIRK;
>>> > + irq_domain_set_affinity(d, &x86_non_ir_cpumask);
>>>
>>> So here it's unconditional
>>
>> Yes, this code is only for the non-remapped case and there's a
>separate
>> arch_create_remap_msi_irq_domain() function a few lines further down
>> which creates the IR-PCI-MSI IRQ domain. So no need for a condition
>> here.
>>
>>> > + if (parent == x86_vector_domain)
>>> > + irq_domain_set_affinity(d, &x86_non_ir_cpumask);
>>>
>>> And here we need a condition again. Completely obvious and
>reviewable - NOT.
>>
>> And HPET may or may not be behind remapping so again needs the
>> condition. I had figured that part was fairly obvious but can note it
>> in the commit comment.
>
>And all of this is completely wrong to begin with.
>
>The information has to property of the relevant irq domains and the
>hierarchy allows you nicely to retrieve it from there instead of
>sprinkling this all over the place.
No. This is not a property of the parent domain per se. Especially if you're
thinking that we could inherit the affinity mask from the parent, then twice no.
This is a property of the MSI domain itself, and how many bits of destination
ID the hardware at *this* level can interpret and pass on to the parent domain.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
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