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From: Catalin Marinas <catalin.marinas@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>,
	Marco Elver <elver@google.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Evgenii Stepanov <eugenis@google.com>,
	linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	Alexander Potapenko <glider@google.com>,
	linux-arm-kernel@lists.infradead.org,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH v13 4/7] arm64: mte: Enable TCO in functions that can read beyond buffer limits
Date: Tue, 23 Feb 2021 13:14:37 +0000	[thread overview]
Message-ID: <20210223131435.GB20769@arm.com> (raw)
In-Reply-To: <20210223124951.GA10563@willie-the-truck>

On Tue, Feb 23, 2021 at 12:49:52PM +0000, Will Deacon wrote:
> On Tue, Feb 23, 2021 at 12:05:32PM +0000, Catalin Marinas wrote:
> > On Tue, Feb 23, 2021 at 10:56:46AM +0000, Vincenzo Frascino wrote:
> > > On 2/22/21 5:58 PM, Catalin Marinas wrote:
> > > > We'll still have an issue with dynamically switching the async/sync mode
> > > > at run-time. Luckily kasan doesn't do this now. The problem is that
> > > > until the last CPU have been switched from async to sync, we can't
> > > > toggle the static label. When switching from sync to async, we need
> > > > to do it on the first CPU being switched.
> > > 
> > > I totally agree on this point. In the case of runtime switching we might need
> > > the rethink completely the strategy and depends a lot on what we want to allow
> > > and what not. For the kernel I imagine we will need to expose something in sysfs
> > > that affects all the cores and then maybe stop_machine() to propagate it to all
> > > the cores. Do you think having some of the cores running in sync mode and some
> > > in async is a viable solution?
> > 
> > stop_machine() is an option indeed. I think it's still possible to run
> > some cores in async while others in sync but the static key here would
> > only be toggled when no async CPUs are left.
> 
> Just as a general point, but if we expose stop_machine() via sysfs we
> probably want to limit that to privileged users so you can't DoS the system
> by spamming into the file.

Definitely. Anyway, that's a later kasan feature if they'd find it
useful. Currently the mode is set at boot from cmdline.

-- 
Catalin

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Alexander Potapenko <glider@google.com>,
	Marco Elver <elver@google.com>,
	Evgenii Stepanov <eugenis@google.com>,
	Branislav Rankov <Branislav.Rankov@arm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Subject: Re: [PATCH v13 4/7] arm64: mte: Enable TCO in functions that can read beyond buffer limits
Date: Tue, 23 Feb 2021 13:14:37 +0000	[thread overview]
Message-ID: <20210223131435.GB20769@arm.com> (raw)
In-Reply-To: <20210223124951.GA10563@willie-the-truck>

On Tue, Feb 23, 2021 at 12:49:52PM +0000, Will Deacon wrote:
> On Tue, Feb 23, 2021 at 12:05:32PM +0000, Catalin Marinas wrote:
> > On Tue, Feb 23, 2021 at 10:56:46AM +0000, Vincenzo Frascino wrote:
> > > On 2/22/21 5:58 PM, Catalin Marinas wrote:
> > > > We'll still have an issue with dynamically switching the async/sync mode
> > > > at run-time. Luckily kasan doesn't do this now. The problem is that
> > > > until the last CPU have been switched from async to sync, we can't
> > > > toggle the static label. When switching from sync to async, we need
> > > > to do it on the first CPU being switched.
> > > 
> > > I totally agree on this point. In the case of runtime switching we might need
> > > the rethink completely the strategy and depends a lot on what we want to allow
> > > and what not. For the kernel I imagine we will need to expose something in sysfs
> > > that affects all the cores and then maybe stop_machine() to propagate it to all
> > > the cores. Do you think having some of the cores running in sync mode and some
> > > in async is a viable solution?
> > 
> > stop_machine() is an option indeed. I think it's still possible to run
> > some cores in async while others in sync but the static key here would
> > only be toggled when no async CPUs are left.
> 
> Just as a general point, but if we expose stop_machine() via sysfs we
> probably want to limit that to privileged users so you can't DoS the system
> by spamming into the file.

Definitely. Anyway, that's a later kasan feature if they'd find it
useful. Currently the mode is set at boot from cmdline.

-- 
Catalin

  reply	other threads:[~2021-02-23 13:16 UTC|newest]

Thread overview: 78+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-11 15:33 [PATCH v13 0/7] arm64: ARMv8.5-A: MTE: Add async mode support Vincenzo Frascino
2021-02-11 15:33 ` Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 1/7] arm64: mte: Add asynchronous " Vincenzo Frascino
2021-02-11 15:33   ` Vincenzo Frascino
2021-02-12 21:21   ` Andrey Konovalov
2021-02-12 21:21     ` Andrey Konovalov
2021-02-22 11:14     ` Vincenzo Frascino
2021-02-22 11:14       ` Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 2/7] kasan: Add KASAN mode kernel parameter Vincenzo Frascino
2021-02-11 15:33   ` Vincenzo Frascino
2021-02-11 17:50   ` Andrey Konovalov
2021-02-11 17:50     ` Andrey Konovalov
2021-02-12 11:26     ` Vincenzo Frascino
2021-02-12 11:26       ` Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 3/7] kasan: Add report for async mode Vincenzo Frascino
2021-02-11 15:33   ` Vincenzo Frascino
2021-02-11 20:03   ` kernel test robot
2021-02-11 20:03     ` kernel test robot
2021-02-11 20:03     ` kernel test robot
2021-02-11 20:13     ` Andrey Konovalov
2021-02-11 20:13       ` Andrey Konovalov
2021-02-11 20:13       ` Andrey Konovalov
2021-02-12 11:25       ` Vincenzo Frascino
2021-02-12 11:25         ` Vincenzo Frascino
2021-02-12 11:25         ` Vincenzo Frascino
2021-02-12 14:47         ` Andrey Konovalov
2021-02-12 14:47           ` Andrey Konovalov
2021-02-12 14:47           ` Andrey Konovalov
2021-02-11 23:03   ` kernel test robot
2021-02-11 23:03     ` kernel test robot
2021-02-11 15:33 ` [PATCH v13 4/7] arm64: mte: Enable TCO in functions that can read beyond buffer limits Vincenzo Frascino
2021-02-11 15:33   ` Vincenzo Frascino
2021-02-12 17:21   ` Catalin Marinas
2021-02-12 17:21     ` Catalin Marinas
2021-02-22 12:08     ` Vincenzo Frascino
2021-02-22 12:08       ` Vincenzo Frascino
2021-02-22 17:58       ` Catalin Marinas
2021-02-22 17:58         ` Catalin Marinas
2021-02-23 10:56         ` Vincenzo Frascino
2021-02-23 10:56           ` Vincenzo Frascino
2021-02-23 12:05           ` Catalin Marinas
2021-02-23 12:05             ` Catalin Marinas
2021-02-23 12:22             ` Vincenzo Frascino
2021-02-23 12:22               ` Vincenzo Frascino
2021-02-23 12:49             ` Will Deacon
2021-02-23 12:49               ` Will Deacon
2021-02-23 13:14               ` Catalin Marinas [this message]
2021-02-23 13:14                 ` Catalin Marinas
2021-02-23 14:25               ` Vincenzo Frascino
2021-02-23 14:25                 ` Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 5/7] arm64: mte: Enable async tag check fault Vincenzo Frascino
2021-02-11 15:33   ` Vincenzo Frascino
2021-02-11 15:33 ` [PATCH v13 6/7] arm64: mte: Report async tag faults before suspend Vincenzo Frascino
2021-02-11 15:33   ` Vincenzo Frascino
2021-02-12 12:00   ` Lorenzo Pieralisi
2021-02-12 12:00     ` Lorenzo Pieralisi
2021-02-12 12:30     ` Lorenzo Pieralisi
2021-02-12 12:30       ` Lorenzo Pieralisi
2021-02-12 13:05       ` Vincenzo Frascino
2021-02-12 13:05         ` Vincenzo Frascino
2021-02-12 13:19     ` Catalin Marinas
2021-02-12 13:19       ` Catalin Marinas
2021-02-12 17:24   ` Catalin Marinas
2021-02-12 17:24     ` Catalin Marinas
2021-02-11 15:33 ` [PATCH v13 7/7] kasan: don't run tests in async mode Vincenzo Frascino
2021-02-11 15:33   ` Vincenzo Frascino
2021-02-12  0:49   ` kernel test robot
2021-02-12  0:49     ` kernel test robot
2021-02-12 17:22   ` Catalin Marinas
2021-02-12 17:22     ` Catalin Marinas
2021-02-12 21:44     ` Andrey Konovalov
2021-02-12 21:44       ` Andrey Konovalov
2021-02-22 11:17       ` Vincenzo Frascino
2021-02-22 11:17         ` Vincenzo Frascino
2021-02-22 13:35         ` Andrey Konovalov
2021-02-22 13:35           ` Andrey Konovalov
2021-02-11 15:45 ` [PATCH v13 0/7] arm64: ARMv8.5-A: MTE: Add async mode support Vincenzo Frascino
2021-02-11 15:45   ` Vincenzo Frascino

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