linux-kernel - Re: [PATCH RFC 11/13] iommu/vt-d: Add an irq

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Date:   Tue, 12 Dec 2023 19:42:13 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 Kernel <x86@...nel.org>,
        iommu@...ts.linux.dev, Lu Baolu <baolu.lu@...ux.intel.com>,
        kvm@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...hat.com>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, maz@...nel.org,
        peterz@...radead.org, seanjc@...gle.com,
        Robin Murphy <robin.murphy@....com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH RFC 11/13] iommu/vt-d: Add an irq_chip for posted MSIs

Hi Thomas,

On Wed, 06 Dec 2023 21:44:02 +0100, Thomas Gleixner <tglx@...utronix.de>
wrote:

> On Sat, Nov 11 2023 at 20:16, Jacob Pan wrote:
> >  static void fill_msi_msg(struct msi_msg *msg, u32 index, u32 subhandle)
> >  {
> >  	memset(msg, 0, sizeof(*msg));
> > @@ -1361,7 +1397,7 @@ static int intel_irq_remapping_alloc(struct
> > irq_domain *domain, 
> >  		irq_data->hwirq = (index << 16) + i;
> >  		irq_data->chip_data = ird;
> > -		irq_data->chip = &intel_ir_chip;
> > +		irq_data->chip = posted_msi_supported() ?
> > &intel_ir_chip_post_msi : &intel_ir_chip;  
> 
> This is just wrong because you change the chip to posted for _ALL_
> domains unconditionally.
> 
> The only domains which want this chip are the PCI/MSI domains. And those
> are distinct from the domains which serve IO/APIC, HPET, no?
> 
> So you can set that chip only for PCI/MSI and just let IO/APIC, HPET
> domains keep the original chip, which spares any modification of the
> IO/APIC domain.
> 
> 
make sense.
-               irq_data->chip = posted_msi_supported() ? &intel_ir_chip_post_msi : &intel_ir_chip;
+               if ((info->type == X86_IRQ_ALLOC_TYPE_PCI_MSI) && posted_msi_supported())
+                       irq_data->chip = &intel_ir_chip_post_msi;
+               else
+                       irq_data->chip = &intel_ir_chip;

Now in IRQ debugfs, I can see the correct IR chips for IOAPIC IRQs and
MSIs.

e.g


domain:  IO-APIC-8
 hwirq:   0x9
 chip:    IR-IO-APIC
  flags:   0x410
             IRQCHIP_SKIP_SET_WAKE
 parent:
    domain:  INTEL-IR-9-13
     hwirq:   0x80000
     chip:    INTEL-IR
      flags:   0x0
     parent:
        domain:  VECTOR


domain:  IR-PCI-MSI-0000:3d:00.4-11
 hwirq:   0x0
 chip:    IR-PCI-MSI-0000:3d:00.4
  flags:   0x430
             IRQCHIP_SKIP_SET_WAKE
             IRQCHIP_ONESHOT_SAFE
 parent:
    domain:  INTEL-IR-4-13
     hwirq:   0x0
     chip:    INTEL-IR-POST
      flags:   0x0
     parent:
        domain:  VECTOR


Thanks,

Jacob