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From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "keescook@chromium.org" <keescook@chromium.org>
Cc: "kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>,
	"luto@kernel.org" <luto@kernel.org>,
	"Hansen, Dave" <dave.hansen@intel.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"rppt@kernel.org" <rppt@kernel.org>,
	"linux-hardening@vger.kernel.org"
	<linux-hardening@vger.kernel.org>,
	"Weiny, Ira" <ira.weiny@intel.com>,
	"Williams, Dan J" <dan.j.williams@intel.com>
Subject: Re: [PATCH RFC 0/9] PKS write protected page tables
Date: Wed, 5 May 2021 19:51:08 +0000	[thread overview]
Message-ID: <16772f10955e1607fcaff9acb701ff27907a11b1.camel@intel.com> (raw)
In-Reply-To: <202105042253.ECBBF6B6@keescook>

On Tue, 2021-05-04 at 23:25 -0700, Kees Cook wrote:
> > infrastructure follow-on’s are planned to enable keys to be set to
> > the same 
> > permissions globally. Since this usage needs a key to be set globally
> > read-only by default, a small temporary solution is hacked up in
> > patch 8. Long 
> > term, PKS protected page tables would use a better and more generic
> > solution 
> > to achieve this.
> > 
> > [1]
> > https://lore.kernel.org/lkml/20210401225833.566238-1-ira.weiny@intel.com/
> 
> Ah, neat!
> 
> > [2]
> > https://lore.kernel.org/lkml/20210405203711.1095940-1-rick.p.edgecombe@intel.com/
> 
> Ooh. What does this do for performance? It sounds like less TLB
> pressure, IIUC?

Yea, less TLB pressure, faster page table walks in theory. There was
some testing that showed having all 4k pages was bad for performance:
https://lore.kernel.org/linux-mm/213b4567-46ce-f116-9cdf-bbd0c884eb3c@linux.intel.com/

I'm not sure exactly how much breakage is needed before problems start
to show up, but there was also someone posting that large amounts of
tracing was noticeable for their workload.

  parent reply	other threads:[~2021-05-05 19:51 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-05  0:30 [PATCH RFC 0/9] PKS write protected page tables Rick Edgecombe
2021-05-05  0:30 ` [PATCH RFC 1/9] list: Support getting most recent element in list_lru Rick Edgecombe
2021-05-05  0:30 ` [PATCH RFC 2/9] list: Support list head not in object for list_lru Rick Edgecombe
2021-05-05  0:30 ` [PATCH RFC 3/9] x86/mm/cpa: Add grouped page allocations Rick Edgecombe
2021-05-05 12:08   ` Mike Rapoport
2021-05-05 13:09     ` Peter Zijlstra
2021-05-05 18:45       ` Mike Rapoport
2021-05-05 21:57         ` Edgecombe, Rick P
2021-05-09  9:39           ` Mike Rapoport
2021-05-10 19:38             ` Edgecombe, Rick P
2021-05-05  0:30 ` [PATCH RFC 4/9] mm: Explicitly zero page table lock ptr Rick Edgecombe
2021-05-05  0:30 ` [PATCH RFC 5/9] x86, mm: Use cache of page tables Rick Edgecombe
2021-05-05  8:51   ` Peter Zijlstra
2021-05-05 12:09     ` Mike Rapoport
2021-05-05 13:19       ` Peter Zijlstra
2021-05-05 21:54         ` Edgecombe, Rick P
2021-05-06 17:59       ` Matthew Wilcox
2021-05-06 18:24   ` Shakeel Butt
2021-05-07 16:27     ` Edgecombe, Rick P
2021-05-05  0:30 ` [PATCH RFC 6/9] x86/mm/cpa: Add set_memory_pks() Rick Edgecombe
2021-05-05  0:30 ` [PATCH RFC 7/9] x86/mm/cpa: Add perm callbacks to grouped pages Rick Edgecombe
2021-05-05  0:30 ` [PATCH RFC 8/9] x86, mm: Protect page tables with PKS Rick Edgecombe
2021-05-05  0:30 ` [PATCH RFC 9/9] x86, cpa: PKS protect direct map page tables Rick Edgecombe
2021-05-05  2:03 ` [PATCH RFC 0/9] PKS write protected " Ira Weiny
2021-05-05  6:25 ` Kees Cook
2021-05-05  8:37   ` Peter Zijlstra
2021-05-05 18:38     ` Kees Cook
2021-05-05 19:51   ` Edgecombe, Rick P [this message]
2021-05-06  0:00   ` Ira Weiny
2021-05-05 11:08 ` Vlastimil Babka
2021-05-05 11:56   ` Peter Zijlstra
2021-05-05 19:46     ` Edgecombe, Rick P

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