linux-kernel - Re: [PATCH] arch/x86: Fix kdump on x86 with physically hotadded CPUs

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Date:   Fri, 7 Oct 2016 10:02:23 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jiri Olsa <jolsa@...hat.com>
cc:     Prarit Bhargava <prarit@...hat.com>, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Len Brown <len.brown@...el.com>, Borislav Petkov <bp@...e.de>,
        Andi Kleen <ak@...ux.intel.com>,
        Juergen Gross <jgross@...e.com>, dyoung@...hat.com,
        Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org
Subject: Re: [PATCH] arch/x86: Fix kdump on x86 with physically hotadded
 CPUs

On Fri, 7 Oct 2016, Jiri Olsa wrote:
> On Thu, Oct 06, 2016 at 11:25:43AM -0400, Prarit Bhargava wrote:
> > I thought about doing this but it seems like every time some driver uses
> > topology_logical_package_id() the driver would have to replicate the error
> > checking code.
> 
> hm, unless we guarantee topology_logical_package_id always
> returns sane values I dont see another way

I did some deeper investigation. So with prarits patch there is only one
possibility left to end up with an empty package id:

SMP Kernel on UP Machine, which has neither ACPI nor MADT. But those
machines are not a problem because they don't use any drivers which would
make use of it. Aside of that for UP we just can set the node of the cpu to
0 and be done with it. I'll pick up Prarits patch and amend it.

Thanks,

	tglx