linux-kernel - RE: [PATCH v2] iommu/vt-d: Allocate DMAR fault interrupts locally

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Date: Mon, 8 Apr 2024 09:00:05 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>, Dimitri Sivanich <sivanich@....com>,
	Thomas Gleixner <tglx@...utronix.de>, Joerg Roedel <joro@...tes.org>, Suravee
 Suthikulpanit <suravee.suthikulpanit@....com>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>, David Woodhouse <dwmw2@...radead.org>,
	Mark Rutland <mark.rutland@....com>, Peter Zijlstra <peterz@...radead.org>,
	Arnd Bergmann <arnd@...db.de>, YueHaibing <yuehaibing@...wei.com>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Steve Wahl
	<steve.wahl@....com>, "Anderson, Russ" <russ.anderson@....com>, Jacob Pan
	<jacob.jun.pan@...ux.intel.com>
Subject: RE: [PATCH v2] iommu/vt-d: Allocate DMAR fault interrupts locally

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Monday, April 8, 2024 3:22 PM
> 
> On 2024/4/8 14:54, Tian, Kevin wrote:
> >> From: Dimitri Sivanich <sivanich@....com>
> >> Sent: Friday, March 22, 2024 4:51 AM
> >>
> >> The Intel IOMMU code currently tries to allocate all DMAR fault interrupt
> >> vectors on the boot cpu.  On large systems with high DMAR counts this
> >> results in vector exhaustion, and most of the vectors are not initially
> >> allocated socket local.
> >>
> >> Instead, have a cpu on each node do the vector allocation for the DMARs
> on
> >> that node.  The boot cpu still does the allocation for its node during its
> >> boot sequence.
> >>
> >> Signed-off-by: Dimitri Sivanich <sivanich@....com>
> >
> > Reviewed-by: Kevin Tian <kevin.tian@...el.com>
> >
> 
> Kevin,
> 
> Jacob has another proposal which shares the irq among all IOMMUs.
> 
> https://lore.kernel.org/linux-iommu/20240403234548.989061-1-
> jacob.jun.pan@...ux.intel.com/
> 
> How do you like this?
> 

I'm a bit concerning about the need of looping all IOMMU's in DMAR
irqchip mask/unmask handlers. this one sounds simpler to me.