On 7 October 2020 13:59:00 BST, Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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.
