Date: Fri, 21 Nov 2014 20:51:43 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
cc: Andy Lutomirski <luto@amacapital.net>,
        Steven Rostedt <rostedt@goodmis.org>, Tejun Heo <tj@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        Peter Zijlstra <peterz@infradead.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Don Zickus <dzickus@redhat.com>, Dave Jones <davej@redhat.com>,
        the arch/x86 maintainers <x86@kernel.org>
Subject: Re: frequent lockups in 3.18rc4
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On Fri, 21 Nov 2014, Linus Torvalds wrote:
> Here's the simplified end result. Again, this is TOTALLY UNTESTED. I
> compiled it and verified that the code generation looks like what I'd
> have expected, but that's literally it.
> 
>   static noinline int vmalloc_fault(unsigned long address)
>   {
>         pgd_t *pgd_dst;
>         pgdval_t pgd_entry;
>         unsigned index = pgd_index(address);
> 
>         if (index < KERNEL_PGD_BOUNDARY)
>                 return -1;
> 
>         pgd_entry = init_mm.pgd[index].pgd;
>         if (!pgd_entry)
>                 return -1;
> 
>         pgd_dst = __va(PAGE_MASK & read_cr3());
>         pgd_dst += index;
> 
>         if (pgd_dst->pgd)
>                 return -1;
> 
>         ACCESS_ONCE(pgd_dst->pgd) = pgd_entry;

This will break paravirt. set_pgd/set_pmd are paravirt functions.

But I'm fine with breaking it, then you just need to change
CONFIG_PARAVIRT to 'def_bool n'

Thanks,

	tglx


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