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From: Stephen Boyd <swboyd@chromium.org>
To: Aaron Durbin <adurbin@chromium.org>,
	Julius Werner <jwerner@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Wei-Ning Huang <wnhuang@chromium.org>,
	Julius Werner <jwerner@chromium.org>,
	Brian Norris <briannorris@chromium.org>,
	samuel@sholland.org
Subject: Re: [PATCH v3 5/7] firmware: coreboot: Remap RAM with memremap() instead of ioremap()
Date: Thu, 09 Aug 2018 15:07:37 -0700
Message-ID: <153385245791.220756.10097093170204882190@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <CAODwPW8x=ghbVpo4q48jh-xGScP+2O_Vt7LTtSqhLvAAnCVXuA@mail.gmail.com>

Quoting Julius Werner (2018-08-09 11:24:29)
> One thing to note is that we still want this space to be mappable by
> userspace applications via /dev/mem, so we need to make sure that
> there's no weird memory type mismatch that causes problems with that.
> Adding Aaron to see if he has any concerns here, since I think he's
> seen something like that in the past (not sure if it was related to
> what this kernel driver does).
> 
> Can you please test this on an x86 Chromebook and run the 'cbmem'
> userspace utility, make sure it doesn't fail after this?

Sure!

> 
> Also, stupid question after taking a step back and looking at this
> again: why do we keep a mapping alive for the lifetime of the driver
> at all? It used to be necessary when this driver was
> find-entry-on-demand, but nowadays it just goes through all entries
> once at probe time and immediately memcpy_fromio()s out all the
> relevant information into (struct coreboot_device)s. After that we're
> done accessing the "real" coreboot table, forever. Why not just unmap
> it again at the end of coreboot_table_init()?

Yes, we just copy everything over so it makes it simpler to just unmap
at the end of coreboot_table_init(). Then userspace is free to make a
questionable mapping into system RAM to find the table itself.

I'll make this change.


  reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-09 17:17 [PATCH v3 0/7] firmware: coreboot: Fix probe and simplify code Stephen Boyd
2018-08-09 17:17 ` [PATCH v3 1/7] firmware: coreboot: Let OF core populate platform device Stephen Boyd
2018-08-09 17:31   ` Brian Norris
2018-08-09 17:17 ` [PATCH v3 2/7] firmware: coreboot: Unmap ioregion on failure Stephen Boyd
2018-08-09 17:49   ` Brian Norris
2018-08-09 19:40     ` Stephen Boyd
2018-08-09 19:52       ` Brian Norris
2018-08-09 23:25         ` Stephen Boyd
2018-08-09 17:17 ` [PATCH v3 3/7] firmware: coreboot: Make bus registration symmetric Stephen Boyd
2018-08-09 18:10   ` Julius Werner
2018-08-09 23:30     ` Stephen Boyd
2018-08-09 17:17 ` [PATCH v3 4/7] firmware: coreboot: Collapse platform drivers into bus core Stephen Boyd
2018-08-09 17:17 ` [PATCH v3 5/7] firmware: coreboot: Remap RAM with memremap() instead of ioremap() Stephen Boyd
2018-08-09 18:24   ` Julius Werner
2018-08-09 22:07     ` Stephen Boyd [this message]
2018-08-09 17:17 ` [PATCH v3 6/7] firmware: coreboot: Only populate devices in coreboot_table_init() Stephen Boyd
2018-08-09 21:02   ` Julius Werner
2018-08-09 23:43     ` Stephen Boyd
2018-08-09 17:17 ` [PATCH v3 7/7] firmware: coreboot: Request table region for exclusive access Stephen Boyd
2018-08-09 21:07   ` Julius Werner
2018-08-09 23:03     ` Stephen Boyd
2018-08-09 23:37       ` Julius Werner
2018-08-09 23:44         ` Julius Werner
2018-08-10  2:54           ` Stephen Boyd
2018-08-10 23:24             ` Stephen Boyd
2018-08-09 18:03 ` [PATCH v3 0/7] firmware: coreboot: Fix probe and simplify code Brian Norris

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