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From: Peter Zijlstra <peterz@infradead.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Marc Gonzalez <marc.w.gonzalez@free.fr>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rafael Wysocki <rjw@rjwysocki.net>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Alexey Brodkin <alexey.brodkin@synopsys.com>,
	Will Deacon <will@kernel.org>,
	Russell King <rmk+kernel@armlinux.org.uk>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Tejun Heo <tj@kernel.org>, Mark Brown <broonie@kernel.org>
Subject: Re: [RFC PATCH v1] devres: align devres.data strictly only for devm_kmalloc()
Date: Fri, 20 Dec 2019 18:13:59 +0100	[thread overview]
Message-ID: <20191220171359.GP2827@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <9be1d523-e92c-836b-b79d-37e880d092a0@arm.com>

On Fri, Dec 20, 2019 at 03:01:03PM +0000, Robin Murphy wrote:
> On 2019-12-20 2:06 pm, Peter Zijlstra wrote:

> > 	data = kmalloc(size + sizeof(struct devres), GFP_KERNEL);
> 
> At this point, you'd still need to special-case devm_kmalloc() to ensure
> size is rounded up to the next ARCH_KMALLOC_MINALIGN granule, or you'd go
> back to the original problem of the struct devres fields potentially sharing
> a cache line with the data buffer. That needs to be avoided, because if the
> devres list is modified while the buffer is mapped for noncoherent DMA
> (which could legitimately happen as they are nominally distinct allocations
> with different owners) there's liable to be data corruption one way or the
> other.

Wait up, why are you allowing non-coherent DMA at less than page size
granularity? Is that really sane? Is this really supported behaviour for
devm ?

WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Alexey Brodkin <alexey.brodkin@synopsys.com>,
	Marc Gonzalez <marc.w.gonzalez@free.fr>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Rafael Wysocki <rjw@rjwysocki.net>,
	LKML <linux-kernel@vger.kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Russell King <rmk+kernel@armlinux.org.uk>,
	Mark Brown <broonie@kernel.org>, Tejun Heo <tj@kernel.org>,
	Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH v1] devres: align devres.data strictly only for devm_kmalloc()
Date: Fri, 20 Dec 2019 18:13:59 +0100	[thread overview]
Message-ID: <20191220171359.GP2827@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <9be1d523-e92c-836b-b79d-37e880d092a0@arm.com>

On Fri, Dec 20, 2019 at 03:01:03PM +0000, Robin Murphy wrote:
> On 2019-12-20 2:06 pm, Peter Zijlstra wrote:

> > 	data = kmalloc(size + sizeof(struct devres), GFP_KERNEL);
> 
> At this point, you'd still need to special-case devm_kmalloc() to ensure
> size is rounded up to the next ARCH_KMALLOC_MINALIGN granule, or you'd go
> back to the original problem of the struct devres fields potentially sharing
> a cache line with the data buffer. That needs to be avoided, because if the
> devres list is modified while the buffer is mapped for noncoherent DMA
> (which could legitimately happen as they are nominally distinct allocations
> with different owners) there's liable to be data corruption one way or the
> other.

Wait up, why are you allowing non-coherent DMA at less than page size
granularity? Is that really sane? Is this really supported behaviour for
devm ?

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

  reply	other threads:[~2019-12-20 17:14 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 15:30 [RFC PATCH v1] devres: align devres.data strictly only for devm_kmalloc() Marc Gonzalez
2019-12-17 15:30 ` Marc Gonzalez
2019-12-17 15:45 ` Greg Kroah-Hartman
2019-12-17 15:45   ` Greg Kroah-Hartman
2019-12-17 16:17 ` Marc Gonzalez
2019-12-17 16:17   ` Marc Gonzalez
2019-12-18 14:20 ` Alexey Brodkin
2019-12-18 14:20   ` Alexey Brodkin
2019-12-18 14:20   ` Alexey Brodkin
2019-12-18 15:40   ` Marc Gonzalez
2019-12-18 15:40     ` Marc Gonzalez
2019-12-18 15:40     ` Marc Gonzalez
2019-12-20 10:19 ` Marc Gonzalez
2019-12-20 10:19   ` Marc Gonzalez
2019-12-20 10:22   ` Greg Kroah-Hartman
2019-12-20 10:22     ` Greg Kroah-Hartman
2019-12-20 10:22     ` Greg Kroah-Hartman
2019-12-20 10:22       ` Greg Kroah-Hartman
2019-12-20 12:05       ` Marc Gonzalez
2019-12-20 12:05         ` Marc Gonzalez
2019-12-20 17:19         ` Peter Zijlstra
2019-12-20 17:19           ` Peter Zijlstra
2019-12-20 14:06   ` Peter Zijlstra
2019-12-20 14:06     ` Peter Zijlstra
2019-12-20 14:16     ` Greg Kroah-Hartman
2019-12-20 14:16       ` Greg Kroah-Hartman
2019-12-20 15:01     ` Robin Murphy
2019-12-20 15:01       ` Robin Murphy
2019-12-20 17:13       ` Peter Zijlstra [this message]
2019-12-20 17:13         ` Peter Zijlstra
2019-12-20 22:02         ` Robin Murphy
2019-12-20 22:02           ` Robin Murphy
2020-01-06 10:05           ` Peter Zijlstra
2020-01-06 10:05             ` Peter Zijlstra
2019-12-20 19:32       ` Alexey Brodkin
2019-12-20 19:32         ` Alexey Brodkin
2019-12-20 19:32         ` Alexey Brodkin
2019-12-20 20:23         ` Peter Zijlstra
2019-12-20 20:23           ` Peter Zijlstra
2019-12-20 20:23           ` Peter Zijlstra
2019-12-20 21:02           ` Alexey Brodkin
2019-12-20 21:02             ` Alexey Brodkin
2019-12-20 21:02             ` Alexey Brodkin
2019-12-20 21:47             ` Dmitry Torokhov
2019-12-20 21:47               ` Dmitry Torokhov
2019-12-20 21:47               ` Dmitry Torokhov

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