linux-kernel - Re: [PATCH 05/15] x86/irq: Reserve a per CPU IDT vector for posted MSIs

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Date: Thu, 4 Apr 2024 10:17:35 -0700
From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
To: Robert Hoo <robert.hoo.linux@...il.com>
Cc: LKML <linux-kernel@...r.kernel.org>, X86 Kernel <x86@...nel.org>, Peter
 Zijlstra <peterz@...radead.org>, iommu@...ts.linux.dev, Thomas Gleixner
 <tglx@...utronix.de>, 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>, Paul Luse
 <paul.e.luse@...el.com>, Dan Williams <dan.j.williams@...el.com>, Jens
 Axboe <axboe@...nel.dk>, Raj Ashok <ashok.raj@...el.com>, "Tian, Kevin"
 <kevin.tian@...el.com>, maz@...nel.org, seanjc@...gle.com, Robin Murphy
 <robin.murphy@....com>, jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 05/15] x86/irq: Reserve a per CPU IDT vector for posted
 MSIs

Hi Robert,

On Thu, 4 Apr 2024 21:38:34 +0800, Robert Hoo <robert.hoo.linux@...il.com>
wrote:

> On 1/27/2024 7:42 AM, Jacob Pan wrote:
> > When posted MSI is enabled, all device MSIs are multiplexed into a
> > single notification vector. MSI handlers will be de-multiplexed at
> > run-time by system software without IDT delivery.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > ---
> >   arch/x86/include/asm/irq_vectors.h | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/include/asm/irq_vectors.h
> > b/arch/x86/include/asm/irq_vectors.h index 3a19904c2db6..08329bef5b1d
> > 100644 --- a/arch/x86/include/asm/irq_vectors.h
> > +++ b/arch/x86/include/asm/irq_vectors.h
> > @@ -99,9 +99,16 @@
> >   
> >   #define LOCAL_TIMER_VECTOR		0xec
> >   
> > +/*
> > + * Posted interrupt notification vector for all device MSIs delivered
> > to
> > + * the host kernel.
> > + */
> > +#define POSTED_MSI_NOTIFICATION_VECTOR	0xeb
> >   #define NR_VECTORS			 256
> >   
> > -#ifdef CONFIG_X86_LOCAL_APIC
> > +#ifdef X86_POSTED_MSI  
> 
> X86_POSTED_MSI --> CONFIG_X86_POSTED_MSI?
Indeed, thanks for catching that!

> > +#define FIRST_SYSTEM_VECTOR
> > POSTED_MSI_NOTIFICATION_VECTOR +#elif defined(CONFIG_X86_LOCAL_APIC)
> >   #define FIRST_SYSTEM_VECTOR		LOCAL_TIMER_VECTOR
> >   #else
> >   #define FIRST_SYSTEM_VECTOR		NR_VECTORS  
> 

Thanks,

Jacob