From: Will Deacon <will@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Alex Belits <abelits@marvell.com>,
"mingo@kernel.org" <mingo@kernel.org>,
"davem@davemloft.net" <davem@davemloft.net>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"rostedt@goodmis.org" <rostedt@goodmis.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
Prasun Kapoor <pkapoor@marvell.com>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
"frederic@kernel.org" <frederic@kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [EXT] Re: [PATCH v3 03/13] task_isolation: add instruction synchronization memory barrier
Date: Tue, 21 Apr 2020 08:41:02 +0100 [thread overview]
Message-ID: <20200421074101.GA15021@willie-the-truck> (raw)
In-Reply-To: <20200420135523.GA18711@willie-the-truck>
On Mon, Apr 20, 2020 at 02:55:23PM +0100, Will Deacon wrote:
> On Mon, Apr 20, 2020 at 01:36:28PM +0100, Mark Rutland wrote:
> > On Mon, Apr 20, 2020 at 01:23:51PM +0100, Will Deacon wrote:
> > > IIUC, we don't need to do anything on arm64 because taking an exception acts
> > > as a context synchronization event, so I don't think you should try to
> > > expose this as a new barrier macro. Instead, just make it a pre-requisite
> > > that architectures need to ensure this behaviour when entering the kernel
> > > from userspace if they are to select HAVE_ARCH_TASK_ISOLATION.
> >
> > The CSE from the exception isn't sufficient here, because it needs to
> > occur after the CPU has re-registered to receive IPIs for
> > kick_all_cpus_sync(). Otherwise there's a window between taking the
> > exception and re-registering where a necessary context synchronization
> > event can be missed. e.g.
> >
> > CPU A CPU B
> > [ Modifies some code ]
> > [ enters exception ]
> > [ D cache maintenance ]
> > [ I cache maintenance ]
> > [ IPI ] // IPI not taken
> > ... [ register for IPI ]
> > [ IPI completes ]
> > [ execute stale code here ]
>
> Thanks.
>
> > However, I think 'IMB' is far too generic, and we should have an arch
> > hook specific to task isolation, as it's far less likely to be abused as
> > IMB will.
>
> What guarantees we don't run any unsynchronised module code between
> exception entry and registering for the IPI? It seems like we'd want that
> code to run as early as possible, e.g. as part of
> task_isolation_user_exit() but that doesn't seem to be what's happening.
Sorry, I guess that's more a question for Alex.
Alex -- do you think we could move the "register for IPI" step earlier
so that it's easier to reason about the code that runs in the dead zone
during exception entry?
Will
next prev parent reply other threads:[~2020-04-21 7:41 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 16:01 [PATCH 00/12] "Task_isolation" mode Alex Belits
2020-03-04 16:03 ` [PATCH 01/12] task_isolation: vmstat: add quiet_vmstat_sync function Alex Belits
2020-03-04 16:04 ` [PATCH 02/12] task_isolation: vmstat: add vmstat_idle function Alex Belits
2020-03-04 16:07 ` [PATCH 03/12] task_isolation: userspace hard isolation from kernel Alex Belits
2020-03-05 18:33 ` Frederic Weisbecker
2020-03-08 5:32 ` [EXT] " Alex Belits
2020-04-28 14:12 ` Marcelo Tosatti
2020-03-06 15:26 ` Frederic Weisbecker
2020-03-08 6:06 ` [EXT] " Alex Belits
2020-03-06 16:00 ` Frederic Weisbecker
2020-03-08 7:16 ` [EXT] " Alex Belits
2020-03-04 16:08 ` [PATCH 04/12] task_isolation: Add task isolation hooks to arch-independent code Alex Belits
2020-03-04 16:09 ` [PATCH 05/12] task_isolation: arch/x86: enable task isolation functionality Alex Belits
2020-03-04 16:10 ` [PATCH 06/12] task_isolation: arch/arm64: " Alex Belits
2020-03-04 16:31 ` Mark Rutland
2020-03-08 4:48 ` [EXT] " Alex Belits
2020-03-04 16:11 ` [PATCH 07/12] task_isolation: arch/arm: " Alex Belits
2020-03-04 16:12 ` [PATCH 08/12] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu() Alex Belits
2020-03-06 16:03 ` Frederic Weisbecker
2020-03-04 16:13 ` [PATCH 09/12] task_isolation: net: don't flush backlog on CPUs running isolated tasks Alex Belits
2020-03-04 16:14 ` [PATCH 10/12] task_isolation: ringbuffer: don't interrupt CPUs running isolated tasks on buffer resize Alex Belits
2020-03-04 16:15 ` [PATCH 11/12] task_isolation: kick_all_cpus_sync: don't kick isolated cpus Alex Belits
2020-03-06 15:34 ` Frederic Weisbecker
2020-03-08 6:48 ` [EXT] " Alex Belits
2020-03-09 2:28 ` Frederic Weisbecker
2020-03-04 16:16 ` [PATCH 12/12] task_isolation: CONFIG_TASK_ISOLATION prevents distribution of jobs to non-housekeeping CPUs Alex Belits
2020-03-08 3:42 ` [PATCH v2 00/12] "Task_isolation" mode Alex Belits
2020-03-08 3:44 ` [PATCH v2 01/12] task_isolation: vmstat: add quiet_vmstat_sync function Alex Belits
2020-03-08 3:46 ` [PATCH v2 02/12] task_isolation: vmstat: add vmstat_idle function Alex Belits
2020-03-08 3:47 ` [PATCH v2 03/12] task_isolation: userspace hard isolation from kernel Alex Belits
[not found] ` <20200307214254.7a8f6c22@hermes.lan>
2020-03-08 7:33 ` [EXT] " Alex Belits
2020-03-27 8:42 ` Marta Rybczynska
2020-04-06 4:31 ` Kevyn-Alexandre Paré
2020-04-06 4:43 ` Kevyn-Alexandre Paré
2020-03-08 3:48 ` [PATCH v2 04/12] task_isolation: Add task isolation hooks to arch-independent code Alex Belits
2020-03-08 3:49 ` [PATCH v2 05/12] task_isolation: arch/x86: enable task isolation functionality Alex Belits
2020-03-08 3:50 ` [PATCH v2 06/12] task_isolation: arch/arm64: " Alex Belits
2020-03-09 16:59 ` Mark Rutland
2020-03-08 3:52 ` [PATCH v2 07/12] task_isolation: arch/arm: " Alex Belits
2020-03-08 3:53 ` [PATCH v2 08/12] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu() Alex Belits
2020-03-08 3:54 ` [PATCH v2 09/12] task_isolation: net: don't flush backlog on CPUs running isolated tasks Alex Belits
2020-03-08 3:55 ` [PATCH v2 10/12] task_isolation: ringbuffer: don't interrupt CPUs running isolated tasks on buffer resize Alex Belits
2020-04-06 4:27 ` Kevyn-Alexandre Paré
2020-03-08 3:56 ` [PATCH v2 11/12] task_isolation: kick_all_cpus_sync: don't kick isolated cpus Alex Belits
2020-03-08 3:57 ` [PATCH v2 12/12] task_isolation: CONFIG_TASK_ISOLATION prevents distribution of jobs to non-housekeeping CPUs Alex Belits
2020-04-09 15:09 ` [PATCH v3 00/13] "Task_isolation" mode Alex Belits
2020-04-09 15:15 ` [PATCH 01/13] task_isolation: vmstat: add quiet_vmstat_sync function Alex Belits
2020-04-09 15:16 ` [PATCH 02/13] task_isolation: vmstat: add vmstat_idle function Alex Belits
2020-04-09 15:17 ` [PATCH v3 03/13] task_isolation: add instruction synchronization memory barrier Alex Belits
2020-04-15 12:44 ` Mark Rutland
2020-04-19 5:02 ` [EXT] " Alex Belits
2020-04-20 12:23 ` Will Deacon
2020-04-20 12:36 ` Mark Rutland
2020-04-20 13:55 ` Will Deacon
2020-04-21 7:41 ` Will Deacon [this message]
2020-04-20 12:45 ` Mark Rutland
2020-04-09 15:20 ` [PATCH v3 04/13] task_isolation: userspace hard isolation from kernel Alex Belits
2020-04-09 18:00 ` Andy Lutomirski
2020-04-19 5:07 ` Alex Belits
2020-04-09 15:21 ` [PATCH 05/13] task_isolation: Add task isolation hooks to arch-independent code Alex Belits
2020-04-09 15:22 ` [PATCH 06/13] task_isolation: arch/x86: enable task isolation functionality Alex Belits
2020-04-09 15:23 ` [PATCH v3 07/13] task_isolation: arch/arm64: " Alex Belits
2020-04-22 12:08 ` Catalin Marinas
2020-04-09 15:24 ` [PATCH v3 08/13] task_isolation: arch/arm: " Alex Belits
2020-04-09 15:25 ` [PATCH v3 09/13] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu() Alex Belits
2020-04-09 15:26 ` [PATCH v3 10/13] task_isolation: net: don't flush backlog on CPUs running isolated tasks Alex Belits
2020-04-09 15:27 ` [PATCH v3 11/13] task_isolation: ringbuffer: don't interrupt CPUs running isolated tasks on buffer resize Alex Belits
2020-04-09 15:27 ` [PATCH v3 12/13] task_isolation: kick_all_cpus_sync: don't kick isolated cpus Alex Belits
2020-04-09 15:28 ` [PATCH v3 13/13] task_isolation: CONFIG_TASK_ISOLATION prevents distribution of jobs to non-housekeeping CPUs Alex Belits
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