linux-kernel - Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first

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Date:	Mon, 4 Jun 2012 22:04:57 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	David Miller <davem@...emloft.net>,
	Tony Luck <tony.luck@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Newbury <steve@...wbury.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first

On Mon, Jun 4, 2012 at 9:50 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Mon, Jun 4, 2012 at 7:37 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>> On Sun, Jun 3, 2012 at 6:05 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>>> On Fri, Jun 1, 2012 at 4:30 PM, Yinghai Lu <yinghai@...nel.org> wrote:
>>>> On Tue, May 29, 2012 at 1:50 PM, H. Peter Anvin <hpa@...or.com> wrote:
>>>>>
>>>>> The bus-side address space should not be more than 32 bits no matter
>>>>> what.  As Bjorn indicates, you seem to be mixing up bus and cpu
>>>>> addresses all over the place.
>>>>
>>>> please check update patches that is using converted pci bus address
>>>> for boundary checking.
>>>
>>> What problem does this fix?  There's significant risk that this
>>> allocation change  will make us trip over something, so it must fix
>>> something to make it worth considering.
>>
>> If we do not enable that, we would not find the problem.
>
> Sorry, that didn't make any sense to me.  I'm hoping you will point us
> to a bug report that is fixed by this patch.

current it only help Steve's test case.

>
>> On one my test setup that _CRS does state 64bit resource range,
>> but when I clear some device resource manually and let kernel allocate
>> high, just then find out those devices does not work with drivers.
>> It turns out _CRS have more big range than what the chipset setting states.
>> with fixing in BIOS, allocate high is working now on that platform.
>
> I didn't understand this either, sorry.  Are you saying that this
> patch helps us work around a BIOS defect?

Help us find out one BIOS defect.

>
>> yeah, how about
>>
>> pci=alloc_high
>>
>> and default to disabled ?
>
> I was actually thinking of something more specific, e.g., a way to
> place one device at an exact address.  I've implemented that a couple
> times already for testing various things.  But maybe a more general
> option like "pci=alloc_high" would make sense, too.

yeah.

>
....
> Linux has a long history of allocating bottom-up.  Windows has a long
> history of allocating top-down.  You're proposing a third alternative,
> allocating bottom-up starting at 4GB for 64-bit BARs.  If we change
> this area, I would prefer something that follows Windows because I
> think it will be closer to what's been tested by Windows.  Do you
> think your alternative is better?

hope we can figure out how windows is making it work.

Steve, Can you check if Windows is working with your test case ?

If it works, we may try do the same thing from Linux, so you will not need to
append "pci=nocrs pci=alloc_high"...

Thanks

Yinghai
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