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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>, Will Deacon <will@kernel.org>,
	Marc Zyngier <maz@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Ard Biesheuvel <ardb@kernel.org>, Christoph Hellwig <hch@lst.de>,
	Isaac Manjarres <isaacmanjarres@google.com>,
	Saravana Kannan <saravanak@google.com>,
	linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 0/2] mm: Allow kmalloc() allocations below ARCH_KMALLOC_MINALIGN
Date: Wed, 26 Oct 2022 08:54:19 +0200	[thread overview]
Message-ID: <Y1jZm8djx8VT7Gc2@kroah.com> (raw)
In-Reply-To: <20221025205247.3264568-1-catalin.marinas@arm.com>

On Tue, Oct 25, 2022 at 09:52:45PM +0100, Catalin Marinas wrote:
> To me, the ideal approach would be __dma annotations on pointers aimed
> at DMA and using kernel tools like sparse to identify them.

As a reviewer of drivers, and a subsystem maintainer, yes, I too would
like this instead.  It would make it much more obvious what is
happening.

> dma_kmalloc() would return such pointers. However, things get muddier
> with scatterlists since functions like sg_set_page() don't have any such
> pointer information (can we mark the offset as __dma instead?).

Drivers don't always call dma_kmalloc() for pointers to pass to dma
controllers.  Heck, I doubt the majority do that at all today, that's
the main problem overall that you are having.

We can take the time and move the kernel to do this, perhaps that is the
real solution that will work best over time here?

thanks,

greg k-h

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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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>, Will Deacon <will@kernel.org>,
	Marc Zyngier <maz@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Ard Biesheuvel <ardb@kernel.org>, Christoph Hellwig <hch@lst.de>,
	Isaac Manjarres <isaacmanjarres@google.com>,
	Saravana Kannan <saravanak@google.com>,
	linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 0/2] mm: Allow kmalloc() allocations below ARCH_KMALLOC_MINALIGN
Date: Wed, 26 Oct 2022 08:54:19 +0200	[thread overview]
Message-ID: <Y1jZm8djx8VT7Gc2@kroah.com> (raw)
In-Reply-To: <20221025205247.3264568-1-catalin.marinas@arm.com>

On Tue, Oct 25, 2022 at 09:52:45PM +0100, Catalin Marinas wrote:
> To me, the ideal approach would be __dma annotations on pointers aimed
> at DMA and using kernel tools like sparse to identify them.

As a reviewer of drivers, and a subsystem maintainer, yes, I too would
like this instead.  It would make it much more obvious what is
happening.

> dma_kmalloc() would return such pointers. However, things get muddier
> with scatterlists since functions like sg_set_page() don't have any such
> pointer information (can we mark the offset as __dma instead?).

Drivers don't always call dma_kmalloc() for pointers to pass to dma
controllers.  Heck, I doubt the majority do that at all today, that's
the main problem overall that you are having.

We can take the time and move the kernel to do this, perhaps that is the
real solution that will work best over time here?

thanks,

greg k-h


  parent reply	other threads:[~2022-10-26  6:54 UTC|newest]

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-25 20:52 [PATCH v2 0/2] mm: Allow kmalloc() allocations below ARCH_KMALLOC_MINALIGN Catalin Marinas
2022-10-25 20:52 ` Catalin Marinas
2022-10-25 20:52 ` [PATCH v2 1/2] mm: slab: Introduce __GFP_PACKED for smaller kmalloc() alignments Catalin Marinas
2022-10-25 20:52   ` Catalin Marinas
2022-10-26  6:39   ` Greg Kroah-Hartman
2022-10-26  6:39     ` Greg Kroah-Hartman
2022-10-26  8:39     ` Catalin Marinas
2022-10-26  8:39       ` Catalin Marinas
2022-10-26  9:49       ` Greg Kroah-Hartman
2022-10-26  9:49         ` Greg Kroah-Hartman
2022-10-26  9:58         ` Catalin Marinas
2022-10-26  9:58           ` Catalin Marinas
2022-10-27 12:11   ` Hyeonggon Yoo
2022-10-27 12:11     ` Hyeonggon Yoo
2022-10-28  7:32     ` Catalin Marinas
2022-10-28  7:32       ` Catalin Marinas
2022-10-25 20:52 ` [PATCH v2 2/2] treewide: Add the __GFP_PACKED flag to several non-DMA kmalloc() allocations Catalin Marinas
2022-10-25 20:52   ` Catalin Marinas
2022-10-26  6:50   ` Greg Kroah-Hartman
2022-10-26  6:50     ` Greg Kroah-Hartman
2022-10-26  9:48     ` Catalin Marinas
2022-10-26  9:48       ` Catalin Marinas
2022-10-26 12:59       ` Greg Kroah-Hartman
2022-10-26 12:59         ` Greg Kroah-Hartman
2022-10-26 17:09         ` Catalin Marinas
2022-10-26 17:09           ` Catalin Marinas
2022-10-26 17:21           ` Greg Kroah-Hartman
2022-10-26 17:21             ` Greg Kroah-Hartman
2022-10-26 17:46       ` Linus Torvalds
2022-10-26 17:46         ` Linus Torvalds
2022-10-27 22:29         ` Catalin Marinas
2022-10-27 22:29           ` Catalin Marinas
2022-10-28  9:37           ` Greg Kroah-Hartman
2022-10-28  9:37             ` Greg Kroah-Hartman
2022-10-28  9:37             ` Greg Kroah-Hartman
2022-10-28  9:37               ` Greg Kroah-Hartman
2022-10-30  8:47               ` Christoph Hellwig
2022-10-30  8:47                 ` Christoph Hellwig
2022-10-30  9:02                 ` Greg Kroah-Hartman
2022-10-30  9:02                   ` Greg Kroah-Hartman
2022-10-30  9:13                   ` Christoph Hellwig
2022-10-30  9:13                     ` Christoph Hellwig
2022-10-30 16:43                     ` Catalin Marinas
2022-10-30 16:43                       ` Catalin Marinas
2022-11-01 10:59                       ` Christoph Hellwig
2022-11-01 10:59                         ` Christoph Hellwig
2022-11-01 17:19                         ` Catalin Marinas
2022-11-01 17:19                           ` Catalin Marinas
2022-11-01 17:24                           ` Christoph Hellwig
2022-11-01 17:24                             ` Christoph Hellwig
2022-11-01 17:32                             ` Catalin Marinas
2022-11-01 17:32                               ` Catalin Marinas
2022-11-01 17:39                               ` Christoph Hellwig
2022-11-01 17:39                                 ` Christoph Hellwig
2022-11-01 19:10                                 ` Isaac Manjarres
2022-11-01 19:10                                   ` Isaac Manjarres
2022-11-02 11:05                                   ` Catalin Marinas
2022-11-02 11:05                                     ` Catalin Marinas
2022-11-02 20:50                                     ` Isaac Manjarres
2022-11-02 20:50                                       ` Isaac Manjarres
2022-11-01 18:14                           ` Robin Murphy
2022-11-01 18:14                             ` Robin Murphy
2022-11-02 13:10                             ` Catalin Marinas
2022-11-02 13:10                               ` Catalin Marinas
2022-10-30  8:46           ` Christoph Hellwig
2022-10-30  8:46             ` Christoph Hellwig
2022-10-30  8:44         ` Christoph Hellwig
2022-10-30  8:44           ` Christoph Hellwig
2022-11-03 16:15       ` Vlastimil Babka
2022-11-03 16:15         ` Vlastimil Babka
2022-11-03 18:03         ` Catalin Marinas
2022-11-03 18:03           ` Catalin Marinas
2022-10-26  6:54 ` Greg Kroah-Hartman [this message]
2022-10-26  6:54   ` [PATCH v2 0/2] mm: Allow kmalloc() allocations below ARCH_KMALLOC_MINALIGN Greg Kroah-Hartman

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