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From: Christoph Hellwig <hch@lst.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Android Kernel Team <kernel-team@android.com>
Subject: Re: [GIT PULL] arm64 fix for 5.14
Date: Fri, 27 Aug 2021 09:40:41 +0200	[thread overview]
Message-ID: <20210827074041.GA24309@lst.de> (raw)
In-Reply-To: <CAHk-=wi8Wxazuq+E4_V0GG4eda0rNpZi76AYWQe7xfPZAAexAQ@mail.gmail.com>

On Thu, Aug 26, 2021 at 11:41:34AM -0700, Linus Torvalds wrote:
> "pfn_valid()" is more about whether you can do a "pfn_to_page()" lookup on it.
> 
> II get the feeling that the dma-mapping code should allow pages that
> are PageReserved() to be mapped - they aren't "ram" in the kernel
> sense.
> 
> Perhaps also make sure it's not the zero page (which is
> PageReserved(), but most definitely RAM).
> 
> In a PC world that would be (for example) the legacy PCI space at
> 0xa0000-0xfffff, but I could easily imagine other platforms having
> other situations.

So what would be the correct check for "this is not actually page backed
normal RAM"?

  reply	other threads:[~2021-08-27  7:40 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26 13:17 Will Deacon
2021-08-26 18:41 ` Linus Torvalds
2021-08-27  7:40   ` Christoph Hellwig [this message]
2021-08-27 17:03     ` Linus Torvalds
2021-08-27 17:10       ` Christoph Hellwig
2021-08-27 17:16         ` Linus Torvalds
2021-08-31 13:31           ` Will Deacon
2021-08-31 19:16             ` David Hildenbrand
2021-08-31 16:56           ` Catalin Marinas
2021-08-26 18:52 ` pr-tracker-bot

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