From: Christoph Hellwig <hch@lst.de>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mike Rapoport <rppt@kernel.org>, Christoph Hellwig <hch@lst.de>,
David Hildenbrand <david@redhat.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: Tue, 21 Sep 2021 10:20:07 +0200 [thread overview]
Message-ID: <20210921082007.GA29121@lst.de> (raw)
In-Reply-To: <YUhpNgwwttW1ewez@arm.com>
On Mon, Sep 20, 2021 at 11:57:58AM +0100, Catalin Marinas wrote:
> > As this WARN_ON(pfn_valid()) is only present in dma_map_resource() it's
> > probably safe to drop it entirely.
>
> I agree, we should drop it. IIUC dma_map_resource() does not create any
> kernel mapping to cause problems with attribute aliasing. You'd need a
> prior devm_ioremap_resource() if you want access to that range from the
> CPU side. For arm64 at least, the latter ends up with a
> pfn_is_map_memory() check.
It doesn't create any new mappings. The only real issue is that it
does the wrong thing for RAM in a way that might not be noticed on
simple (x86/PC) platforms.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mike Rapoport <rppt@kernel.org>, Christoph Hellwig <hch@lst.de>,
David Hildenbrand <david@redhat.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: Tue, 21 Sep 2021 10:20:07 +0200 [thread overview]
Message-ID: <20210921082007.GA29121@lst.de> (raw)
In-Reply-To: <YUhpNgwwttW1ewez@arm.com>
On Mon, Sep 20, 2021 at 11:57:58AM +0100, Catalin Marinas wrote:
> > As this WARN_ON(pfn_valid()) is only present in dma_map_resource() it's
> > probably safe to drop it entirely.
>
> I agree, we should drop it. IIUC dma_map_resource() does not create any
> kernel mapping to cause problems with attribute aliasing. You'd need a
> prior devm_ioremap_resource() if you want access to that range from the
> CPU side. For arm64 at least, the latter ends up with a
> pfn_is_map_memory() check.
It doesn't create any new mappings. The only real issue is that it
does the wrong thing for RAM in a way that might not be noticed on
simple (x86/PC) platforms.
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next prev parent reply other threads:[~2021-09-21 8:20 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 [this message]
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
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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