linux-kernel - Re: [tip:x86/platform] x86/intel/quark: Switch off CR4.PGE so TLB flush uses CR3 instead

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Message-ID: <5422EA13.1080706@nexus-software.ie>
Date:	Wed, 24 Sep 2014 16:58:11 +0100
From:	Bryan O'Donoghue <pure.logic@...us-software.ie>
To:	"H. Peter Anvin" <hpa@...or.com>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	stable@...r.kernel.org, bp@...en8.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/platform] x86/intel/quark: Switch off CR4.PGE so TLB
 flush uses CR3 instead


>
> I believe there is one more change needed: there is a __flush_tlb_all()
> in the early code which gets executed before the above code runs; the
> easiest fix is to just add a __flush_tlb() immediately after it.
>
> This should have been pushed upstream, and not stayed in the BSP kernel.

Peter.

You're talking about void __init setup_arch() right ?

The code looks like this

load_cr3(swapper_pg_dir);
__flush_tlb_all();

Note that on Quark the method to invalidate the TLB is by reloading CR3 
- which is immediately prior to __flush_tlb_all();

So __flush_tlb_all(); will do nothing but that's OK since load_cr3() 
already flushed the TLB - including any PTE with PGE set


Best,
Bryan
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