From: David Hildenbrand <david@redhat.com>
To: Christoph Hellwig <hch@lst.de>, Mike Rapoport <rppt@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Robin Murphy <robin.murphy@arm.com>,
Alex Bee <knaerzche@gmail.com>, Will Deacon <will@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [BUG 5.14] arm64/mm: dma memory mapping fails (in some cases)
Date: Mon, 20 Sep 2021 13:13:32 +0200 [thread overview]
Message-ID: <71b7d1b5-4a5f-9053-b22b-4d946cbf6d6e@redhat.com> (raw)
In-Reply-To: <20210918051843.GA16104@lst.de>
On 18.09.21 07:18, Christoph Hellwig wrote:
> On Sat, Sep 18, 2021 at 12:22:47AM +0300, Mike Rapoport wrote:
>> I did some digging and it seems that the most "generic" way to check if a
>> page is in RAM is page_is_ram(). It's not 100% bullet proof as it'll give
>> false negatives for architectures that do not register "System RAM", but
>> those are not using dma_map_resource() anyway and, apparently, never would.
>
> The downside of page_is_ram is that it looks really expensiv for
> something done at dma mapping time.
>
There would be ways to speed it up, similar to
https://lkml.kernel.org/r/20210902160919.25683-2-david@redhat.com
but the end result is still walking a list. Question would be, how much
that overhead matters in practice.
--
Thanks,
David / dhildenb
WARNING: multiple messages have this Message-ID (diff)
From: David Hildenbrand <david@redhat.com>
To: Christoph Hellwig <hch@lst.de>, Mike Rapoport <rppt@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Robin Murphy <robin.murphy@arm.com>,
Alex Bee <knaerzche@gmail.com>, Will Deacon <will@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [BUG 5.14] arm64/mm: dma memory mapping fails (in some cases)
Date: Mon, 20 Sep 2021 13:13:32 +0200 [thread overview]
Message-ID: <71b7d1b5-4a5f-9053-b22b-4d946cbf6d6e@redhat.com> (raw)
In-Reply-To: <20210918051843.GA16104@lst.de>
On 18.09.21 07:18, Christoph Hellwig wrote:
> On Sat, Sep 18, 2021 at 12:22:47AM +0300, Mike Rapoport wrote:
>> I did some digging and it seems that the most "generic" way to check if a
>> page is in RAM is page_is_ram(). It's not 100% bullet proof as it'll give
>> false negatives for architectures that do not register "System RAM", but
>> those are not using dma_map_resource() anyway and, apparently, never would.
>
> The downside of page_is_ram is that it looks really expensiv for
> something done at dma mapping time.
>
There would be ways to speed it up, similar to
https://lkml.kernel.org/r/20210902160919.25683-2-david@redhat.com
but the end result is still walking a list. Question would be, how much
that overhead matters in practice.
--
Thanks,
David / dhildenb
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-09-20 11:13 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-24 13:40 [BUG 5.14] arm64/mm: dma memory mapping fails (in some cases) Alex Bee
2021-08-24 13:40 ` Alex Bee
2021-08-24 17:37 ` Catalin Marinas
2021-08-24 17:37 ` Catalin Marinas
2021-08-24 18:06 ` Robin Murphy
2021-08-24 18:06 ` Robin Murphy
2021-08-24 18:28 ` Mike Rapoport
2021-08-24 18:28 ` Mike Rapoport
2021-08-24 18:46 ` Robin Murphy
2021-08-24 18:46 ` Robin Murphy
2021-08-24 18:59 ` David Hildenbrand
2021-08-24 18:59 ` David Hildenbrand
2021-08-25 10:20 ` Catalin Marinas
2021-08-25 10:20 ` Catalin Marinas
2021-08-25 10:28 ` Will Deacon
2021-08-25 10:28 ` Will Deacon
2021-08-25 10:32 ` Will Deacon
2021-08-25 10:32 ` Will Deacon
2021-08-25 10:33 ` Robin Murphy
2021-08-25 10:33 ` Robin Murphy
2021-08-25 10:38 ` David Hildenbrand
2021-08-25 10:38 ` David Hildenbrand
2021-08-25 10:54 ` Mike Rapoport
2021-08-25 10:54 ` Mike Rapoport
2021-08-25 10:55 ` Catalin Marinas
2021-08-25 10:55 ` Catalin Marinas
2021-08-25 11:12 ` David Hildenbrand
2021-08-25 11:12 ` David Hildenbrand
2021-08-25 17:15 ` Catalin Marinas
2021-08-25 17:15 ` Catalin Marinas
2021-08-25 10:58 ` Robin Murphy
2021-08-25 10:58 ` Robin Murphy
2021-08-25 11:21 ` David Hildenbrand
2021-08-25 11:21 ` David Hildenbrand
2021-08-25 10:52 ` Mike Rapoport
2021-08-25 10:52 ` Mike Rapoport
2021-09-17 21:22 ` Mike Rapoport
2021-09-17 21:22 ` Mike Rapoport
2021-09-18 5:18 ` Christoph Hellwig
2021-09-18 5:18 ` Christoph Hellwig
2021-09-18 8:37 ` Mike Rapoport
2021-09-18 8:37 ` Mike Rapoport
2021-09-18 11:39 ` Mike Rapoport
2021-09-18 11:39 ` Mike Rapoport
2021-09-20 10:57 ` Catalin Marinas
2021-09-20 10:57 ` Catalin Marinas
2021-09-21 8:20 ` Christoph Hellwig
2021-09-21 8:20 ` Christoph Hellwig
2021-09-21 9:34 ` Mike Rapoport
2021-09-21 9:34 ` Mike Rapoport
2021-09-21 15:38 ` Christoph Hellwig
2021-09-21 15:38 ` Christoph Hellwig
2021-09-22 7:22 ` Mike Rapoport
2021-09-22 7:22 ` Mike Rapoport
2021-09-20 11:13 ` David Hildenbrand [this message]
2021-09-20 11:13 ` David Hildenbrand
2021-08-24 20:14 ` Alex Bee
2021-08-24 20:14 ` Alex Bee
2021-08-25 4:39 ` Mike Rapoport
2021-08-25 4:39 ` Mike Rapoport
2021-08-25 10:00 ` Alex Bee
2021-08-25 10:00 ` Alex Bee
2021-08-24 20:07 ` Alex Bee
2021-08-24 20:07 ` Alex Bee
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