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From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	x86@kernel.org, Song Liu <songliubraving@fb.com>,
	Joerg Roedel <jroedel@suse.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Rik van Riel <riel@surriel.com>
Subject: Re: [patch 0/2] x86/mm/pti: Robustness updates
Date: Wed, 28 Aug 2019 18:03:42 +0200	[thread overview]
Message-ID: <20190828160342.GF17205@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20190828142445.454151604@linutronix.de>

On Wed, Aug 28, 2019 at 04:24:45PM +0200, Thomas Gleixner wrote:
> Following up on the discussions around the patch Song submitted to 'cure' a
> iTLB related performance regression, I picked up Song's patch which makes
> clone_page_tables() more robust by handling unaligned addresses proper and
> added one which prevents calling into the PTI code when PTI is enabled
> compile time, but disabled at runtime (command line or CPU not affected).
> 
> There is no point in calling into those PTI functions unconditionally. The
> resulting page tables are the same before and after the change which makes
> sense as the code clones the kernel page table into the secondary page
> table space which is available but not used when PTI is boot time disabled.
> 
> But even if it does not do damage today, this could have nasty side effect
> when the PTI code is changed, extended etc. later.
> 

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

      parent reply	other threads:[~2019-08-28 16:04 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-28 14:24 [patch 0/2] x86/mm/pti: Robustness updates Thomas Gleixner
2019-08-28 14:24 ` [patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable() Thomas Gleixner
2019-08-28 15:46   ` Dave Hansen
2019-08-28 15:51     ` Thomas Gleixner
2019-08-28 17:58       ` Song Liu
2019-08-28 20:05         ` Thomas Gleixner
2019-08-28 20:32           ` Song Liu
2019-08-28 22:31             ` [PATCH] x86/mm/cpa: Prevent large page split when ftrace flips RW on kernel text Thomas Gleixner
2019-08-28 23:03               ` Song Liu
2019-08-29 13:01               ` Peter Zijlstra
2019-08-29 18:55               ` [tip: x86/urgent] " tip-bot2 for Thomas Gleixner
2019-08-28 18:58   ` [patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable() Ingo Molnar
2019-08-28 19:45     ` Thomas Gleixner
2019-08-28 20:54   ` [patch V2 " Thomas Gleixner
2019-08-28 21:52     ` Thomas Gleixner
2019-08-28 21:54     ` [patch V3 " Thomas Gleixner
2019-08-28 23:22       ` Ingo Molnar
2019-08-29 19:02       ` [tip: x86/pti] " tip-bot2 for Song Liu
2019-08-30 10:24       ` [patch V3 1/2] " Joerg Roedel
2019-08-28 14:24 ` [patch 2/2] x86/mm/pti: Do not invoke PTI functions when PTI is disabled Thomas Gleixner
2019-08-28 15:47   ` Dave Hansen
2019-08-28 17:49   ` Song Liu
2019-08-28 19:00   ` Ingo Molnar
2019-08-29 19:02   ` [tip: x86/pti] " tip-bot2 for Thomas Gleixner
2019-08-30 10:25   ` [patch 2/2] " Joerg Roedel
2019-08-28 16:03 ` Peter Zijlstra [this message]

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