linux-kernel - Re: [PATCH 2/2] Intel-IOMMU, intr-remap: source-id checking

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Date:	Mon, 11 May 2009 15:20:27 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Han, Weidong" <weidong.han@...el.com>
Cc:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH 2/2] Intel-IOMMU, intr-remap: source-id checking


* Han, Weidong <weidong.han@...el.com> wrote:

> Siddha, Suresh B wrote:
> > On Wed, 2009-05-06 at 23:16 -0700, Han, Weidong wrote:
> >> @@ -634,6 +694,44 @@ static int ir_parse_ioapic_scope(struct
> >>  			       acpi_dmar_header *header, " 0x%Lx\n",
> >>  			       scope->enumeration_id, drhd->address);
> >> 
> >> +			bus = pci_find_bus(drhd->segment, scope->bus);
> >> +			path = (struct acpi_dmar_pci_path *)(scope + 1); +			count =
> >> (scope->length - +				 sizeof(struct acpi_dmar_device_scope))
> >> +				/ sizeof(struct acpi_dmar_pci_path);
> >> +
> >> +			while (count) {
> >> +				if (pdev)
> >> +					pci_dev_put(pdev);
> >> +
> >> +				if (!bus)
> >> +					break;
> >> +
> >> +				pdev = pci_get_slot(bus,
> >> +					PCI_DEVFN(path->dev, path->fn));
> >> +				if (!pdev)
> >> +					break;
> > 
> > ir_parse_ioapic_scope() happens very early in the boot. So, I 
> > don't think we can do the pci related discovery here.
> > 
> 
> Thanks for your pointing it out. It should enable the source-id 
> checking for io-apic's after the pci subsystem is up. I will 
> change it.

Note, there's ways to do early PCI quirks too, check 
arch/x86/kernel/early-quirks.c. It's done by reading the PCI 
configuration space directly via a careful early-capable subset of 
the PCI config space APIs.

But it's a method of last resort.

	Ingo
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