• Yinghai Lu's avatar
    x86: disable the GART early, 64-bit · aaf23042
    Yinghai Lu authored
    For K8 system: 4G RAM with memory hole remapping enabled, or more than
    4G RAM installed.
    
    when try to use kexec second kernel, and the first doesn't include
    gart_shutdown. the second kernel could have different aper position than
    the first kernel. and second kernel could use that hole as RAM that is
    still used by GART set by the first kernel. esp. when try to kexec
    2.6.24 with sparse mem enable from previous kernel (from RHEL 5 or SLES
    10). the new kernel will use aper by GART (set by first kernel) for
    vmemmap. and after new kernel setting one new GART. the position will be
    real RAM. the _mapcount set is lost.
    
    Bad page state in process 'swapper'
    page:ffffe2000e600020 flags:0x0000000000000000 mapping:0000000000000000 mapcount:1 count:0
    Trying to fix it up, but a reboot is needed
    Backtrace:
    Pid: 0, comm: swapper Not tainted 2.6.24-rc7-smp-gcdf71a10-dirty #13
    
    Call Trace:
     [<ffffffff8026401f>] bad_page+0x63/0x8d
     [<ffffffff80264169>] __free_pages_ok+0x7c/0x2a5
     [<ffffffff80ba75d1>] free_all_bootmem_core+0xd0/0x198
     [<ffffffff80ba3a42>] numa_free_all_bootmem+0x3b/0x76
     [<ffffffff80ba3461>] mem_init+0x3b/0x152
     [<ffffffff80b959d3>] start_kernel+0x236/0x2c2
     [<ffffffff80b9511a>] _sinittext+0x11a/0x121
    
    and
     [ffffe2000e600000-ffffe2000e7fffff] PMD ->ffff81001c200000 on node 0
    phys addr is : 0x1c200000
    
    RHEL 5.1 kernel -53 said:
    PCI-DMA: aperture base @ 1c000000 size 65536 KB
    
    new kernel said:
    Mapping aperture over 65536 KB of RAM @ 3c000000
    
    So could try to disable that GART if possible.
    
    According to Ingo
    
    > hm, i'm wondering, instead of modifying the GART, why dont we simply
    > _detect_ whatever GART settings we have inherited, and propagate that
    > into our e820 maps? I.e. if there's inconsistency, then punch that out
    > from the memory maps and just dont use that memory.
    >
    > that way it would not matter whether the GART settings came from a [old
    > or crashing] Linux kernel that has not called gart_iommu_shutdown(), or
    > whether it's a BIOS that has set up an aperture hole inconsistent with
    > the memory map it passed. (or the memory map we _think_ i tried to pass
    > us)
    >
    > it would also be more robust to only read and do a memory map quirk
    > based on that, than actively trying to change the GART so early in the
    > bootup. Later on we have to re-enable the GART _anyway_ and have to
    > punch a hole for it.
    >
    > and as a bonus, we would have shored up our defenses against crappy
    > BIOSes as well.
    
    add e820 modification for gart inconsistent setting.
    
    gart_fix_e820=off could be used to disable e820 fix.
    Signed-off-by: default avatarYinghai Lu <yinghai.lu@sun.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    aaf23042
gart.h 812 Bytes