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From: Thomas Gleixner <tglx@linutronix.de>
To: Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	Borislav Petkov <bp@alien8.de>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>,
	Daniel Gruss <daniel.gruss@iaik.tugraz.at>,
	Hugh Dickins <hughd@google.com>, Kees Cook <keescook@google.com>,
	Linux-MM <linux-mm@kvack.org>,
	michael.schwarz@iaik.tugraz.at, moritz.lipp@iaik.tugraz.at,
	richard.fellner@student.tugraz.at
Subject: Re: [patch V2 1/5] x86/kaiser: Respect disabled CPU features
Date: Mon, 27 Nov 2017 14:18:44 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.20.1711271416410.1799@nanos> (raw)
In-Reply-To: <CAMzpN2joDWU41SpNTu30pnOsZbdNcDMiCZ99HBy53SFVwvxMuw@mail.gmail.com>

On Mon, 27 Nov 2017, Brian Gerst wrote:
> On Mon, Nov 27, 2017 at 6:47 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Mon, 27 Nov 2017, Peter Zijlstra wrote:
> >> On Mon, Nov 27, 2017 at 12:14:04AM +0100, Thomas Gleixner wrote:
> >> > PAGE_NX and PAGE_GLOBAL might be not supported or disabled on the command
> >> > line, but KAISER sets them unconditionally.
> >>
> >> So KAISER is x86_64 only, right? AFAIK there is no x86_64 without NX
> >> support. So would it not make sense to mandate NX for KAISER?, that is
> >> instead of making "noexec" + KAISER work, make "noexec" kill KAISER +
> >> emit a warning.
> >
> > OTOH, disabling NX is a simple way to verify that DEBUG_WX works correctly
> > also on the shadow maps.
> >
> > But surely we can drop the PAGE_GLOBAL thing, as all 64bit systems have it.
> 
> I seem to recall that some virtualized environments (maybe Xen?) don't
> support global pages.

Uuurg. Ok, we leave it as is for now. Better safe than sorry. It does no
harm.

Thanks,

	tglx

WARNING: multiple messages have this Message-ID
From: Thomas Gleixner <tglx@linutronix.de>
To: Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	Borislav Petkov <bp@alien8.de>,
	Denys Vlasenko <dvlasenk@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Rik van Riel <riel@redhat.com>,
	Daniel Gruss <daniel.gruss@iaik.tugraz.at>,
	Hugh Dickins <hughd@google.com>, Kees Cook <keescook@google.com>,
	Linux-MM <linux-mm@kvack.org>,
	michael.schwarz@iaik.tugraz.at, moritz.lipp@iaik.tugraz.at,
	richard.fellner@student.tugraz.at
Subject: Re: [patch V2 1/5] x86/kaiser: Respect disabled CPU features
Date: Mon, 27 Nov 2017 14:18:44 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.20.1711271416410.1799@nanos> (raw)
In-Reply-To: <CAMzpN2joDWU41SpNTu30pnOsZbdNcDMiCZ99HBy53SFVwvxMuw@mail.gmail.com>

On Mon, 27 Nov 2017, Brian Gerst wrote:
> On Mon, Nov 27, 2017 at 6:47 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Mon, 27 Nov 2017, Peter Zijlstra wrote:
> >> On Mon, Nov 27, 2017 at 12:14:04AM +0100, Thomas Gleixner wrote:
> >> > PAGE_NX and PAGE_GLOBAL might be not supported or disabled on the command
> >> > line, but KAISER sets them unconditionally.
> >>
> >> So KAISER is x86_64 only, right? AFAIK there is no x86_64 without NX
> >> support. So would it not make sense to mandate NX for KAISER?, that is
> >> instead of making "noexec" + KAISER work, make "noexec" kill KAISER +
> >> emit a warning.
> >
> > OTOH, disabling NX is a simple way to verify that DEBUG_WX works correctly
> > also on the shadow maps.
> >
> > But surely we can drop the PAGE_GLOBAL thing, as all 64bit systems have it.
> 
> I seem to recall that some virtualized environments (maybe Xen?) don't
> support global pages.

Uuurg. Ok, we leave it as is for now. Better safe than sorry. It does no
harm.

Thanks,

	tglx

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  reply	other threads:[~2017-11-27 13:18 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-26 23:14 [patch V2 0/5] x86/kaiser: Boot time disabling and debug support Thomas Gleixner
2017-11-26 23:14 ` Thomas Gleixner
2017-11-26 23:14 ` [patch V2 1/5] x86/kaiser: Respect disabled CPU features Thomas Gleixner
2017-11-26 23:14   ` Thomas Gleixner
2017-11-27  9:57   ` Peter Zijlstra
2017-11-27  9:57     ` Peter Zijlstra
2017-11-27 11:47     ` Thomas Gleixner
2017-11-27 11:47       ` Thomas Gleixner
2017-11-27 12:31       ` Brian Gerst
2017-11-27 12:31         ` Brian Gerst
2017-11-27 13:18         ` Thomas Gleixner [this message]
2017-11-27 13:18           ` Thomas Gleixner
2017-11-27 18:11   ` Dave Hansen
2017-11-27 18:11     ` Dave Hansen
2017-11-27 18:37     ` Kees Cook
2017-11-27 18:37       ` Kees Cook
2017-11-26 23:14 ` [patch V2 2/5] x86/kaiser: Simplify disabling of global pages Thomas Gleixner
2017-11-26 23:14   ` Thomas Gleixner
2017-11-27 11:49   ` Thomas Gleixner
2017-11-27 11:49     ` Thomas Gleixner
2017-11-27 18:15   ` Dave Hansen
2017-11-27 18:15     ` Dave Hansen
2017-11-27 20:28     ` Thomas Gleixner
2017-11-27 20:28       ` Thomas Gleixner
2017-11-26 23:14 ` [patch V2 3/5] x86/dump_pagetables: Check KAISER shadow page table for WX pages Thomas Gleixner
2017-11-26 23:14   ` Thomas Gleixner
2017-11-27 18:17   ` Dave Hansen
2017-11-27 18:17     ` Dave Hansen
2017-11-26 23:14 ` [patch V2 4/5] x86/mm/debug_pagetables: Allow dumping current pagetables Thomas Gleixner
2017-11-26 23:14   ` Thomas Gleixner
2017-11-27  9:41   ` Peter Zijlstra
2017-11-27  9:41     ` Peter Zijlstra
2017-11-27 10:06     ` [PATCH] vfs: Add PERM_* symbolic helpers for common file mode/permissions Ingo Molnar
2017-11-27 10:06       ` Ingo Molnar
2017-11-27 19:21       ` Linus Torvalds
2017-11-27 19:21         ` Linus Torvalds
2017-11-28 10:54         ` Ingo Molnar
2017-11-28 10:54           ` Ingo Molnar
2017-11-28 11:12         ` Ingo Molnar
2017-11-28 11:12           ` Ingo Molnar
2017-11-29  8:52           ` Michael Ellerman
2017-11-29  8:52             ` Michael Ellerman
2017-11-27 18:18   ` [patch V2 4/5] x86/mm/debug_pagetables: Allow dumping current pagetables Dave Hansen
2017-11-27 18:18     ` Dave Hansen
2017-11-26 23:14 ` [patch V2 5/5] x86/kaiser: Add boottime disable switch Thomas Gleixner
2017-11-26 23:14   ` Thomas Gleixner
2017-11-27  9:48   ` Peter Zijlstra
2017-11-27  9:48     ` Peter Zijlstra
2017-11-27 10:22     ` Peter Zijlstra
2017-11-27 10:22       ` Peter Zijlstra
2017-11-27 11:50       ` Thomas Gleixner
2017-11-27 11:50         ` Thomas Gleixner
2017-11-27 12:49         ` Peter Zijlstra
2017-11-27 12:49           ` Peter Zijlstra
2017-11-27 21:43       ` Peter Zijlstra
2017-11-27 21:43         ` Peter Zijlstra
2017-11-27 18:22   ` Dave Hansen
2017-11-27 18:22     ` Dave Hansen
2017-11-27 19:00     ` Thomas Gleixner
2017-11-27 19:00       ` Thomas Gleixner
2017-11-27 19:18       ` Josh Poimboeuf
2017-11-27 19:18         ` Josh Poimboeuf
2017-11-27 20:47         ` Thomas Gleixner
2017-11-27 20:47           ` Thomas Gleixner

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