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

From: Bjorn Helgaas <bhelgaas@google.com>
To: Steven Newbury <steve@snewbury.org.uk>
Cc: Yinghai Lu <yinghai@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
	David Miller <davem@davemloft.net>,
	Tony Luck <tony.luck@intel.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first
Date: Wed, 6 Jun 2012 09:18:13 -0700	[thread overview]
Message-ID: <CAErSpo7BwkiVugTn9A8pM-OViRnNZ+az-pf9vjxYnd=iZ3AuSQ@mail.gmail.com> (raw)
In-Reply-To: <1338975852.5858.2.camel@Nokia-N900>

On Wed, Jun 6, 2012 at 2:44 AM, Steven Newbury <steve@snewbury.org.uk> wrote:
> On Tue,   5 Jun 2012, 06:04:57 BST, Yinghai Lu <yinghai@kernel.org> wrote:
>> > 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"...
>>
> Unfortunately I don't have a 64 bit version of Windows to test with.  Vista(32 bit) fails to even boot when docked, hot-plugging fails to allocate resources, but at least doesn't crash.
>
> From what I've read about the (64 bit) Windows allocation stragegy it's closer to Yinghai's method than the Linux default, preferring 64 bit resources (>4G) when possible.  I'll try to find the specification document again.

Here's the host bridge info from the BIOS (from
https://bugzilla.kernel.org/show_bug.cgi?id=10461 attachment
https://bugzilla.kernel.org/attachment.cgi?id=72869):

ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff])
pci_root PNP0A03:00: host bridge window [io  0x0000-0x0cf7]
pci_root PNP0A03:00: host bridge window [io  0x0d00-0xffff]
pci_root PNP0A03:00: host bridge window [mem 0x000a0000-0x000bffff]
pci_root PNP0A03:00: host bridge window [mem 0x000d0000-0x000dffff]
pci_root PNP0A03:00: host bridge window [mem 0xe0000000-0xf7ffffff]
pci_root PNP0A03:00: host bridge window [mem 0xfc000000-0xfebfffff]
pci_root PNP0A03:00: host bridge window [mem 0xfec10000-0xfecfffff]
pci_root PNP0A03:00: host bridge window [mem 0xfed1c000-0xfed1ffff]
pci_root PNP0A03:00: host bridge window [mem 0xfed90000-0xfed9ffff]
pci_root PNP0A03:00: host bridge window [mem 0xfed40000-0xfed44fff]
pci_root PNP0A03:00: host bridge window [mem 0xfeda7000-0xfedfffff]
pci_root PNP0A03:00: host bridge window [mem 0xfee10000-0xff9fffff]
pci_root PNP0A03:00: host bridge window [mem 0xffc00000-0xffdfffff]

There's no aperture above 4GB.  So I don't think any version of
Windows will ever assign a BAR above 4GB.