linux-kernel - Re: [PATCH] - UV fix for size of hub mappings

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Message-ID: <20080927195615.GA244243@sgi.com>
Date:	Sat, 27 Sep 2008 14:56:16 -0500
From:	Jack Steiner <steiner@....com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Yinghai Lu <yhlu.kernel@...il.com>
Subject: Re: [PATCH] - UV fix for size of hub mappings

On Sat, Sep 27, 2008 at 07:42:33PM +0200, Ingo Molnar wrote:
> 
> * Jack Steiner <steiner@....com> wrote:
> 
> > Fix the size of the mappings of UV hub registers. Size must be a 
> > function of the maximum node number within the SSI.
> > 
> > Signed-off-by: Jack Steiner <steiner@....com>
> 
> applied to tip/x86/uv, thanks Jack!
> 
> i'm wondering, the code still has a couple of ZZZ fixmes like:
> 
>  #ifdef ZZZ              /* Needs x2apic patch */
>  static void uv_send_IPI_self(int vector)
>  {
>          apic_write(APIC_SELF_IPI, vector);
>  }
>  #endif
> 
> x2apic support is available in tip/master, so it would be nice to glue 
> UV to generic x2apic support properly and remove duplication and fixmes.

Good point. I'll send the fixes to you early next week. Recently,
I've been focused on a distro release which is still waiting for
the x2apic code. However, I don't need to wait to fix this upstream...


> For example, do we really need apic_x2apic_uv_x, or could we use 
> apic_x2apic_cluster?

Unfortunately, we really need a uv genapic. IPIs on large UV systems
can't use an x2apic model. Because of the size of our large systems, APICIDs
in the cpu MSRs are not globally unique. We have a special feature
in the UV chipset that must be used for on large systems for IPIs.
Small & medium sized system can and do use the x2apic genapic.

--- jack
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