linux-kernel - Re: [PATCH -v2 1/2] x86: Reserve [0xa0000, 0x100000] in e820 map

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Message-ID: <4BC4F03C.1020707@oracle.com>
Date:	Tue, 13 Apr 2010 15:29:16 -0700
From:	Yinghai <yinghai.lu@...cle.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Bjorn Helgaas <bjorn.helgaas@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andy Isaacson <adi@...apodia.org>, guenter.roeck@...csson.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Renninger <trenn@...e.de>
Subject: Re: [PATCH -v2 1/2] x86: Reserve [0xa0000, 0x100000] in e820 map

On 04/13/2010 02:58 PM, H. Peter Anvin wrote:
> On 04/13/2010 02:42 PM, Yinghai wrote:
>> On 04/13/2010 02:18 PM, H. Peter Anvin wrote:
>>> On 04/13/2010 02:11 PM, Yinghai wrote:
>>>>>
>>>>> I guess the real question (which I haven't looked at myself) is if the
>>>>> E820_RESERVED -> BUSY will cause an explicitly assigned BAR from being
>>>>> moved.  That's bad, not so much for this particular range, but from BARs
>>>>> which may be assigned by SMM.  Hacking that up in a simulator
>>>>> (Qemu/Bochs) and testing it is probably on the to do list...
>>>>
>>>> no, if some device BAR fall in that range, it should still use that range, and will not be relocated.
>>>>
>>>> will update the change log.
>>>>
>>>
>>> Good, that's what we want.
>>
>> the driver for that device later can not use pci_request_region(). because that region is BUSY already.
>>
> 
> That's not good (in general - for devices in this particular range it's
> not such a big deal, but it is potentially really bad for devices marked
> reserved for them not to be moved.)
> 
> We have talked about a need to resolve this before.

current code for mmio that is just below 4g, if some PCI BAR use that range, and those range is falling into E820_RESERVED,

those range still can be claimed, but driver can not use pci_request_region() later.

So We still
1. rely that BIOS does not reserve the [0xa0000, 0xe0000)
2. kernel only reserve the range when we make sure these is legacy device on that range.

YH
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