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From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Hansen <dave.hansen@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	x86@kernel.org, Song Liu <songliubraving@fb.com>,
	Joerg Roedel <jroedel@suse.de>, Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Rik van Riel <riel@surriel.com>
Subject: Re: [patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable()
Date: Wed, 28 Aug 2019 17:51:10 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1908281750410.1938@nanos.tec.linutronix.de> (raw)
In-Reply-To: <55bb026c-5d54-6ebf-608f-3f376fbec4e5@intel.com>

On Wed, 28 Aug 2019, Dave Hansen wrote:
> On 8/28/19 7:24 AM, Thomas Gleixner wrote:
> > From: Song Liu <songliubraving@fb.com>
> > 
> > pti_clone_pmds() assumes that the supplied address is either:
> > 
> >  - properly PUD/PMD aligned
> > or
> >  - the address is actually mapped which means that independent
> >    of the mapping level (PUD/PMD/PTE) the next higher mapping
> >    exist.
> > 
> > If that's not the case the unaligned address can be incremented by PUD or
> > PMD size wrongly. All callers supply mapped and/or aligned addresses, but
> > for robustness sake, it's better to handle that case proper and to emit a
> > warning.
> 
> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
> 
> Song, did you ever root-cause the performance regression?  I thought
> there were still some mysteries there.

See Peter's series to rework the ftrace code patching ...


  reply	other threads:[~2019-08-28 15:51 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 [this message]
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 ` [patch 0/2] x86/mm/pti: Robustness updates Peter Zijlstra

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