linux-kernel - [PATCH 0/3] PTI for x86-32 Fixes and Updates

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Date:   Fri, 20 Jul 2018 18:22:21 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>, aliguori@...zon.com,
        daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, Pavel Machek <pavel@....cz>,
        "David H . Gutteridge" <dhgutteridge@...patico.ca>,
        jroedel@...e.de, Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>, joro@...tes.org
Subject: [PATCH 0/3] PTI for x86-32 Fixes and Updates

Hi,

here are 3 patches which update the PTI-x86-32 patches recently merged
into the tip-tree. The patches are ordered by importance:

	Patch 1: Very important, it fixes a vmalloc-fault in NMI context
		 when PTI is enabled. This is pretty unlikely to hit
		 when starting perf on an idle machine, which is why I
		 didn't find it earlier in my testing. I always started
		 'perf top' first :/ But when I start 'perf top' last
		 when the kernel-compile already runs, it hits almost
		 immediatly.

	Patch 2: Fix the 'from-kernel-check' in SWITCH_TO_KERNEL_STACK
	         to also take VM86 into account. This is not strictly
		 necessary because the slow-path also works for VM86
		 mode but it is not how the code was intended to work.
		 And it breaks when Patch 3 is applied on-top.

	Patch 3: Implement the reduced copying in the paranoid
		 entry/exit path as suggested by Andy Lutomirski while
		 reviewing version 7 of the original patches.

I have the x86/tip branch with these patches on-top running my test for
6h now, with no issues so far. So for now it looks like there are no
scheduling points or irq-enabled sections reached from the paranoid
entry/exit paths and we always return to the entry-stack we came from.

I keep the test running over the weekend at least.

Please review.

[ If Patch 1 looks good to the maintainers I suggest applying it soon,
  before too many linux-next testers run into this issue. It is actually
  the reason why I send out the patches _now_ and didn't wait until next
  week when the other two patches got more testing from my side. ]

Thanks,

	Joerg

Joerg Roedel (3):
  perf/core: Make sure the ring-buffer is mapped in all page-tables
  x86/entry/32: Check for VM86 mode in slow-path check
  x86/entry/32: Copy only ptregs on paranoid entry/exit path

 arch/x86/entry/entry_32.S   | 82 ++++++++++++++++++++++++++-------------------
 kernel/events/ring_buffer.c | 10 ++++++
 2 files changed, 58 insertions(+), 34 deletions(-)

-- 
2.7.4