linux-kernel - RE: [PATCH v2 05/13] x86/irq: Reserve a per CPU IDT vector for posted MSIs

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Message-ID: <BN9PR11MB527615053A012DB570999FB08C082@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Tue, 16 Apr 2024 03:45:20 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: Jacob Pan <jacob.jun.pan@...ux.intel.com>, LKML
	<linux-kernel@...r.kernel.org>, X86 Kernel <x86@...nel.org>, Peter Zijlstra
	<peterz@...radead.org>, "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	Thomas Gleixner <tglx@...utronix.de>, Lu Baolu <baolu.lu@...ux.intel.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Hansen, Dave"
	<dave.hansen@...el.com>, Joerg Roedel <joro@...tes.org>, Peter Anvin
	<hpa@...or.com>, Borislav Petkov <bp@...en8.de>, Ingo Molnar
	<mingo@...hat.com>, "Luse, Paul E" <paul.e.luse@...el.com>, "Williams, Dan J"
	<dan.j.williams@...el.com>, Jens Axboe <axboe@...nel.dk>, "Raj, Ashok"
	<ashok.raj@...el.com>, "maz@...nel.org" <maz@...nel.org>, Robin Murphy
	<robin.murphy@....com>, "jim.harris@...sung.com" <jim.harris@...sung.com>,
	"a.manzanares@...sung.com" <a.manzanares@...sung.com>, Bjorn Helgaas
	<helgaas@...nel.org>, "Zeng, Guang" <guang.zeng@...el.com>,
	"robert.hoo.linux@...il.com" <robert.hoo.linux@...il.com>
Subject: RE: [PATCH v2 05/13] x86/irq: Reserve a per CPU IDT vector for posted
 MSIs

> From: Sean Christopherson <seanjc@...gle.com>
> Sent: Friday, April 12, 2024 10:28 PM
> 
> On Fri, Apr 12, 2024, Kevin Tian wrote:
> > > From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > > Sent: Saturday, April 6, 2024 6:31 AM
> > >
> > > +/*
> > > + * Posted interrupt notification vector for all device MSIs delivered to
> > > + * the host kernel.
> > > + */
> > > +#define POSTED_MSI_NOTIFICATION_VECTOR	0xeb
> > >  #define NR_VECTORS			 256
> > >
> >
> > Every interrupt is kind of a notification.
> 
> FWIW, I find value in having "notification" in the name to differentiate
> between
> the IRQ that is notifying the CPU that there's a posted IRQ to be processed,
> and
> the posted IRQ itself.

IMHO one who knows posted msi doesn't need the extra
'notification' in the name to differentiate.

one who doesn't know what posted msi is anyway needs to
look at the surrounding code including the above comment.
having 'notification' in the name alone doesn't really help.

but I'd not hold strong on this... 😊