linux-kernel - Re: [BUG 2.6.31-rc1] HIGHMEM64G causes hang in PCI init on 32-bit x86

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Date:	Tue, 30 Jun 2009 10:45:40 +0200
From:	Mikael Pettersson <mikpe@...uu.se>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mikael Pettersson <mikpe@...uu.se>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Matthew Wilcox <matthew@....cx>,
	Grant Grundler <grundler@...isc-linux.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org
Subject: Re: [BUG 2.6.31-rc1] HIGHMEM64G causes hang in PCI init on 32-bit
 x86

Yinghai Lu writes:
 > Linus Torvalds wrote:
 > > 
 > > On Mon, 29 Jun 2009, Yinghai Lu wrote:
 > >> +		end = round_up(start, ram_alignment(start)) - 1;
 > >> +		if (start > (resource_size_t)end)
 > >>  			continue;
 > >> -		reserve_region_with_split(&iomem_resource, start,
 > >> -						  end - 1, "RAM buffer");
 > >> +		reserve_region_with_split(&iomem_resource, (resource_size_t)start,
 > >> +					  (resource_size_t)end, "RAM buffer");
 > > 
 > > Hmm. You shouldn't need the casts with reserve_region_with_split(), and 
 > > they just make things uglier.
 > > 
 > > Also, I wonder if we should do something like this instead
 > > 
 > > 	#define MAX_RESOURCE_SIZE ((resource_size_t)-1)
 > > 
 > > 	...
 > > 	end = round_up(start, ram_alignment(start)) - 1;
 > > 	if (end > MAX_RESOURCE_SIZE)
 > > 		end = MAX_RESOURCE_SIZE;
 > > 	if (start > end)
 > > 		continue;
 > > 
 > > Because otherwise we'll just be ignoring resources that cross the resource 
 > > size boundary, which sounds wrong.
 > > 
 > > We _could_ have a RAM resource that crosses the 4GB boundary, after all.
 > > 
 > > Yeah, it doesn't happen much in practice, because usually the 3G-4G range 
 > > is left for PCI mappings etc, so we might never hit this in practice, but 
 > > still, this sounds like a more correct thing to do.
 > > 
 > > It also avoids the cast. We simply cap the end to the max that 
 > > 'resource_size_t' can hold.
 > 
 > Mikael, please try this on your system, and send out /proc/iomem
 > 
 > Thanks
 > 
 > Yinghai
 > 
 > [PATCH] x86: add boundary check for 32bit res before expand e820 resource to alignment
 > 
 > fix hang with HIGHMEM_64G and 32bit resource.
 > 
 > according to hpa and Linus, use (resource_size_t)-1 to fend off big ranges.
 > 
 > Signed-off-by: Yinghai Lu <yinghai@...nel.org>

Thanks, 2.6.31-rc1 vanilla (which didn't boot) plus this one does boot.
/proc/iomem now looks as follows:

00000000-0009ebff : System RAM
0009ec00-0009ffff : reserved
000a0000-000bffff : Video RAM area
000c0000-000ccfff : Video ROM
000e4000-000fffff : reserved
  000f0000-000fffff : System ROM
00100000-7ff8ffff : System RAM
  00100000-002e022e : Kernel code
  002e022f-0038aaf7 : Kernel data
  003d8000-003fc9f3 : Kernel bss
7ff90000-7ff9dfff : ACPI Tables
7ff9e000-7ffdffff : ACPI Non-volatile Storage
7ffe0000-7fffffff : reserved
80000000-800000ff : 0000:00:1f.3
bff00000-dfefffff : PCI Bus 0000:01
  c0000000-cfffffff : 0000:01:00.0
e0000000-efffffff : PCI MMCONFIG 0 [00-ff]
  e0000000-efffffff : pnp 00:0e
febfe000-febfec00 : pnp 00:09
fec00000-fec00fff : IOAPIC 0
  fec00000-fec00fff : pnp 00:0b
fed00000-fed003ff : HPET 0
fed14000-fed19fff : pnp 00:01
fed1c000-fed1ffff : pnp 00:09
fed20000-fed8ffff : pnp 00:09
fee00000-fee00fff : Local APIC
  fee00000-fee00fff : reserved
    fee00000-fee00fff : pnp 00:0b
ff800000-ff8fffff : PCI Bus 0000:01
  ff8c0000-ff8dffff : 0000:01:00.0
  ff8e0000-ff8effff : 0000:01:00.1
  ff8f0000-ff8fffff : 0000:01:00.0
ff900000-ff9fffff : PCI Bus 0000:02
  ff9ffc00-ff9ffcff : 0000:02:02.0
    ff9ffc00-ff9ffcff : 8139too
ffaf8000-ffafbfff : 0000:00:1b.0
  ffaf8000-ffafbfff : ICH HD audio
ffaff000-ffaff3ff : 0000:00:1d.7
  ffaff000-ffaff3ff : ehci_hcd
ffaff400-ffaff7ff : 0000:00:1a.7
  ffaff400-ffaff7ff : ehci_hcd
ffaff800-ffafffff : 0000:00:1f.2
  ffaff800-ffafffff : ahci
ffb00000-ffffffff : reserved
  ffb00000-ffbfffff : pnp 00:09
  fff00000-fffffffe : pnp 00:09
100000000-1ffffffff : System RAM
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