From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752792AbaIYJf5 (ORCPT ); Thu, 25 Sep 2014 05:35:57 -0400 Received: from outbound-smtp05.blacknight.com ([81.17.249.38]:37826 "EHLO outbound-smtp05.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751719AbaIYJfz (ORCPT ); Thu, 25 Sep 2014 05:35:55 -0400 Message-ID: <5423E1F7.5010000@nexus-software.ie> Date: Thu, 25 Sep 2014 10:35:51 +0100 From: "Bryan O'Donoghue" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.1 MIME-Version: 1.0 To: Ingo Molnar CC: hpa@zytor.com, mingo@redhat.com, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: Quark: Flush TLB via CR3 not CR4.PGE in setup_arch() References: <1411578452-4609-1-git-send-email-pure.logic@nexus-software.ie> <20140925045755.GA20431@gmail.com> In-Reply-To: <20140925045755.GA20431@gmail.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c >> index 41ead8d..1d2396a 100644 >> --- a/arch/x86/kernel/setup.c >> +++ b/arch/x86/kernel/setup.c >> @@ -879,7 +879,10 @@ void __init setup_arch(char **cmdline_p) >> KERNEL_PGD_PTRS); >> >> load_cr3(swapper_pg_dir); >> - __flush_tlb_all(); >> + if (boot_cpu_data.x86 == 5 && boot_cpu_data.x86_model == 9) >> + __flush_tlb(); >> + else >> + __flush_tlb_all(); > > So why not make __flush_tlb_all() Quark-quirk-aware and be done > with it, instead of having to validate every single > __flush_tlb_all() user? > > Quark breaks the x86 'flush all TLBs' semantics - the way to fix > it is to restore those semantics, not to sprinkle the breakage > all around the code ... Hi Ingo. We have made __flush_tlb_all() Quark aware - because the previous patch we applied to arch/x86/kernel/cpu/intel.c ee1b5b165c0a2f04d2107e634e51f05d0eb107de + if (c->x86 == 5 && c->x86_model == 9) { + pr_info("Disabling PGE capability bit\n"); + setup_clear_cpu_cap(X86_FEATURE_PGE); + } will cause cpu_has_pge() to be false and then the flush_tlb_all code will take the path we want __flush_tlb not __flush_tlb_global static inline void __flush_tlb_all(void) { if (cpu_has_pge) __flush_tlb_global(); else __flush_tlb(); } The code in setup_arch runs before the cpu_has_pge bit been clobbered. The commit you did 02276a3a677d681f0cd227d7111c71fdbce23832 just adds a comment to setup_arch to indicate the behaviour we are relying on setup_arch() { load_cr3(swapper_pg_dir); /* this will flush the TLB on Quark */ __flush_tlb_all(); /*cpu_has_pge() is true at this point*/ ...... /* this is where we latch the cpu cabability bits */ early_cpu_init(); } -- BOD