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2006-03-25[PATCH] x86_64: group memnodemap and memnodeshift in a memnode structureEric Dumazet
pfn_to_page() and others need to access both memnode_shift and the very first bytes of memnodemap[]. If we force memnode_shift to be just before the memnodemap array, we can reduce the memory footprint to one cache line instead of two for most setups. This patch introduce a 'memnode' structure where shift and map[] are carefully placed. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25[PATCH] x86_64: Try to allocate node memmap near the end of nodeAndi Kleen
This fixes problems with very large nodes (over 128GB) filling up all of the first 4GB with their mem_map and not leaving enough space for the swiotlb. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25[PATCH] x86_64: Add __init to fixmap functions that are only called during bootAndi Kleen
Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25[PATCH] x86_64: Implement early DMI scanningAndi Kleen
There are more and more cases where we need to know DMI information early to work around bugs. i386 already had early DMI scanning, but x86-64 didn't. Implement this now. This required some cleanup in the i386 code. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25[PATCH] x86_64: prefetch the mmap_sem in the fault pathArjan van de Ven
In a micro-benchmark that stresses the pagefault path, the down_read_trylock on the mmap_sem showed up quite high on the profile. Turns out this lock is bouncing between cpus quite a bit and thus is cache-cold a lot. This patch prefetches the lock (for write) as early as possible (and before some other somewhat expensive operations). With this patch, the down_read_trylock basically fell out of the top of profile. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25[PATCH] x86_64: actively synchronize vmalloc area when registering certain ↵Jan Beulich
callbacks While the modular aspect of the respective i386 patch doesn't apply to x86-64 (as the top level page directory entry is shared between modules and the base kernel), handlers registered with register_die_notifier() are still under similar constraints for touching ioremap()ed or vmalloc()ed memory. The likelihood of this problem becoming visible is of course significantly lower, as the assigned virtual addresses would have to cross a 2**39 byte boundary. This is because the callback gets invoked (a) in the page fault path before the top level page table propagation gets carried out (hence a fault to propagate the top level page table entry/entries mapping to module's code/data would nest infinitly) and (b) in the NMI path, where nested faults must absolutely not happen, since otherwise the IRET from the nested fault re-enables NMIs, potentially resulting in nested NMI occurences. Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25[PATCH] x86_64: Rename struct node in x86-64 NUMA code to struct bootnodeAndi Kleen
It conflicts with the struct node in node.h Actually the x86-64 version was there first, but .. Suggested by Jan Beulich Cc: jbeulich@novell.com Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-25[PATCH] x86_64: Use correct PUD for memory hotaddJan Beulich
Memory >39bits has a different PUD. Cc: "Tolentino, Matthew E" <matthew.e.tolentino@intel.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-22[PATCH] remove set_page_count() outside mm/Nick Piggin
set_page_count usage outside mm/ is limited to setting the refcount to 1. Remove set_page_count from outside mm/, and replace those users with init_page_count() and set_page_refcounted(). This allows more debug checking, and tighter control on how code is allowed to play around with page->_count. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-22[PATCH] x86_64: pageattr remove __put_pageNick Piggin
Remove page_count and __put_page from x86-64 pageattr Signed-off-by: Nick Piggin <npiggin@suse.de> Acked-by: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-22[PATCH] x86_64: pageattr use single listNick Piggin
Use page->lru.next to implement the singly linked list of pages rather than the struct deferred_page which needs to be allocated and freed for each page. Signed-off-by: Nick Piggin <npiggin@suse.de> Acked-by: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-17[PATCH] x86_64: Always pass full number of nodes to NUMA hash computationAndi Kleen
Previously the numa hash code would be confused by holes in the node space and stop early. This is the first part of the fix for the non boot issue with empty nodes on Opterons. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-17[PATCH] x86_64: Relax SRAT covers all memory check a bitAndi Kleen
Code was refusing good SRATs because about 12K got lost somewhere. Allow less than 1MB of difference before rejecting it. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-15[PATCH] x86_64: early initialization of cpu_to_nodeDaniel Yeisley
The early initialization of cpu_to_node code as it is now only updates the cpu_to_node array, and does not update cpu_pda()->nodemember. This will cause numa_node_id() to return 0 on systems where CPU 0 is not on Node 0. This leads to a kernel panic in slab.c. I've tested the patch below on a 16 processor x86_64 ES7000-600 server, and no longer see the panic I saw with the original 2.6.16-rc3. Signed-off-by: Dan Yeisley <dan.yeisley@unisys.com> Acked-by: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-04[PATCH] x86_64: minor odering correction to dump_pagetable()Jan Beulich
Checking of the validity of pointers should be consistently done before dereferencing the pointer. Signed-Off-By: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-04[PATCH] x86_64: Do more checking in the SRAT header codeAndi Kleen
- Check if the processor/memory affinity entries are long enough according to the ACPI 3.0 spec. - Ignore memory affinity entries that define a zero length region. All based on BIOS issues found in the field @) Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-04[PATCH] x86_64: Clear more state when ignoring empty node in SRAT parsingAndi Kleen
Might fix boot failures on systems with empty PXMs in SRAT Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-16[PATCH] x86_64: add x86-64 support for memory hot-addMatt Tolentino
Add x86-64 specific memory hot-add functions, Kconfig options, and runtime kernel page table update functions to make hot-add usable on x86-64 machines. Also, fixup the nefarious conditional locking and exports pointed out by Andi. Tested on Intel and IBM x86-64 memory hot-add capable systems. Signed-off-by: Matt Tolentino <matthew.e.tolentino@intel.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-16[PATCH] x86_64: Flexmap for 32bit and randomized mappings for 64bitAndi Kleen
Another try at this. For 32bit follow the 32bit implementation from Ingo - mappings are growing down from the end of stack now and vary randomly by 1GB. Randomized mappings for 64bit just vary the normal mmap break by 1TB. I didn't bother implementing full flex mmap for 64bit because it shouldn't be needed there. Cc: mingo@elte.hu Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-16x86-64: fix initrd freeingLinus Torvalds
The comparison of the initrd start address against "&_end" is unnecessary and incorrect. Make it match the x86 code that just compares the passed-in arguments. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-16[PATCH] x86_64: Don't try to put kernel page tables beyond ZONE_DMA32.Andi Kleen
For not fully explained reasons it broke mem=... on several setups. Also minor cleanup. Cc: axboe@suse.de Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Allow kernel page tables upto the end of memoryAndi Kleen
Previously they would be only allocated before the kernel text at 1MB. This limited the maximum supported memory to 128GB. Now allow the e820 allocator to put them everywhere. Try to put them beyond any DMA zones to avoid filling them up. This should free some GFP_DMA memory compared to earlier kernels. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Move NUMA page_to_pfn/pfn_to_page functions out of lineAndi Kleen
Saves about ~18K .text in defconfig There would be more optimization potential, but that's for later. Suggestion originally from Bill Irwin. Fix from Andy Whitcroft. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Node local pda take 2 -- cpu_pda preparationRavikiran G Thirumalai
Helper patch to change cpu_pda users to use macros to access cpu_pda instead of the cpu_pda[] array. Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org> Signed-off-by: Shai Fultheim <shai@scalex86.org> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Early initialization of cpu_to_nodeRavikiran Thirumalai
Patch enables early intialization of cpu_to_node. apicid_to_node is built by reading the SRAT table, from acpi_numa_init with ACPI_NUMA and k8_scan_nodes with K8_NUMA. x86_cpu_to_apicid is built by parsing the ACPI MADT table, from acpi_boot_init. We combine these two tables and setup cpu_to_node. Early intialization helps the static per_cpu_areas in getting pages from correct node. Change since last release: Do not initialize early init_cpu_to_node for faking node cases. Patch tested on TYAN dual core 4P board with K8 only, ACPI_NUMA. Tested on EM64T NUMA. Also tested with numa=off, numa=fake, and running a kernel compiled with NUMA on a regular EM64 2 way SMP. Signed-off-by: Alok N Kataria <alokk@calsoftinc.com> Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org> Signed-off-by: Shai Fultheim <shai@scalex86.org> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Use function pointers to call DMA mapping functionsMuli Ben-Yehuda
AK: I hacked Muli's original patch a lot and there were a lot of changes - all bugs are probably to blame on me now. There were also some changes in the fall back behaviour for swiotlb - in particular it doesn't try to use GFP_DMA now anymore. Also all DMA mapping operations use the same core dma_alloc_coherent code with proper fallbacks now. And various other changes and cleanups. Known problems: iommu=force swiotlb=force together breaks needs more testing. This patch cleans up x86_64's DMA mapping dispatching code. Right now we have three possible IOMMU types: AGP GART, swiotlb and nommu, and in the future we will also have Xen's x86_64 swiotlb and other HW IOMMUs for x86_64. In order to support all of them cleanly, this patch: - introduces a struct dma_mapping_ops with function pointers for each of the DMA mapping operations of gart (AMD HW IOMMU), swiotlb (software IOMMU) and nommu (no IOMMU). - gets rid of: if (swiotlb) return swiotlb_xxx(); - PCI_DMA_BUS_IS_PHYS is now checked against the dma_ops being set This makes swiotlb faster by avoiding double copying in some cases. Signed-Off-By: Muli Ben-Yehuda <mulix@mulix.org> Signed-Off-By: Jon D. Mason <jdmason@us.ibm.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Reject SRAT tables that don't cover all memoryAndi Kleen
Broken BIOS on Iwill 8way systems reports these and it causes the bootmem allocator to crash. Add a sanity check if all the PXMs in the SRAT table cover all memory as reported by e820. If the sanity check fails the SRAT is rejected and the code will fall back to discover the NUMA topology using the K8 northbridge registers when applicable. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Clean up some printks in NUMA codeAndi Kleen
Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Fix up coding style in numa.cAndi Kleen
No functional changes Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Fix off by one in IOMMU checkAndi Kleen
Fix off by one when checking if the machine has enougn memory to need IOMMU This caused the IOMMUs to be needlessly enabled for mem=4G Based on a patch from Jon Mason Signed-off-by: jdmason@us.ibm.com Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Convert page fault error codes to symbolic constants.Andi Kleen
Much better to deal with these than with the magic numbers. And remove the comment describing the bits - kernel source is no replacement for an architecture manual. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Remove unnecessary case from the page fault handlerAndi Kleen
Don't need to do the vmalloc check for the module range because its PML4 is shared with the kernel text. Also removed an unnecessary TLB flush. Pointed out by Jan Beulich Cc: jbeulich@novell.com Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Return -1 for unknown PCI bus affinityAndi Kleen
When we don't know the node a PCI bus is connected to return -1. This matches the generic code. Noticed by Ravikiran G Thirumalai <kiran@scalex86.org> Cc: Ravikiran G Thirumalai <kiran@scalex86.org> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Validate SLIT tableAndi Kleen
A lot of Opteron BIOS just pass 10 in all SLIT entries (10 is the normalized unit). This is actually worse than the default heuristic because it leads to pci_distance not knowing the difference between local and remote nodes anymore. This messes up some NUMA heuristics in generic code. In this case it's better to fall back to the default heuristic which just does nodea == nodeb ? 10 : 20. This patch does some basic sanity checking on the SLIT and only accepts the SLIT when it passes. Invariants enforced are: - Node to itself shall be 10 - Any other distance shouldn't be 10 - Distances smaller than 10 are illegal Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: Adjust page fault handlingJan Beulich
Adjust page fault protection error check before considering it to be a vmalloc synchronization candidate. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-11[PATCH] x86_64: make trap information available to die notification handlersJan Beulich
This adjusts things so that handlers of the die() notifier will have sufficient information about the trap currently being handled. It also adjusts the notify_die() prototype to (again) match that of i386. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-06[PATCH] x86/x86_64: mark rodata section read-only: x86-64 supportArjan van de Ven
x86-64 specific parts to make the .rodata section read only Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-06[PATCH] x86/x86_64: mark rodata section read only: generic x86-64 bugfixArjan van de Ven
Bug fix required for the .rodata work on x86-64: when change_page_attr() and friends need to break up a 2Mb page into 4Kb pages, it always set the NX bit on the PMD, which causes the cpu to consider the entire 2Mb region to be NX regardless of the actual PTE perms. This is fine in general, with one big exception: the 2Mb page that covers the last part of the kernel .text! The fix is to not invent a new permission for the new PMD entry, but to just inherit the existing one minus the PSE bit. Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-29[PATCH] x86_64: Fix incorrect node_present_pages on NUMARavikiran G Thirumalai
Currently, we do not pass the correct start_pfn to e820_hole_size, to calculate holes. Following patch fixes that. The bug results in incorrect number of node_present_pages for each pgdat and causes ugly output in /sys and probably VM inbalances. Signed-off-by: Alok N Kataria <alokk@calsoftinc.com> Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org> Signed-off-by: Andi Kleen <ak@suse.de> Sighed-off-by: Shair Fultheim <shai@scalex86.org> Sighed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-15[PATCH] i386,amd64: ioremap.c __iomem annotationsAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-12[PATCH] x86_64: Bug correction in populate_memnodemap()Eric Dumazet
As reported by Keith Mannthey, there are problems in populate_memnodemap() The bug was that the compute_hash_shift() was returning 31, with incorrect initialization of memnodemap[] To correct the bug, we must use (1UL << shift) instead of (1 << shift) to avoid an integer overflow, and we must check that shift < 64 to avoid an infinite loop. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-12[PATCH] i386/x86-64: Don't call change_page_attr with a spinlock heldAndi Kleen
It's illegal because it can sleep. Use a two step lookup scheme instead. First look up the vm_struct, then change the direct mapping, then finally unmap it. That's ok because nobody can change the particular virtual address range as long as the vm_struct is still in the global list. Also added some LinuxDoc documentation to iounmap. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14[PATCH] x86_64: Fix sparse memBob Picco
Fix up booting with sparse mem enabled. Otherwise it would just cause an early PANIC at boot. Signed-off-by: Bob Picco <bob.picco@hp.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14[PATCH] x86_64: Remove CONFIG_CHECKING and add command line option for ↵Andi Kleen
pagefault tracing CONFIG_CHECKING covered some debugging code used in the early times of the port. But it wasn't even SMP safe for quite some time and the bugs it checked for seem to be gone. This patch removes all the code to verify GS at kernel entry. There haven't been any new bugs in this area for a long time. Previously it also covered the sysctl for the page fault tracing. That didn't make much sense because that code was unconditionally compiled in. I made that a boot option now because it is typically only useful at boot. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14[PATCH] x86_64: Make node boundaries consistentMagnus Damm
The current x86_64 NUMA memory code is inconsequent when it comes to node memory ranges. The exact behaviour varies depending on which config option that is used. setup_node_bootmem() has start and end as arguments and these are used to calculate the size of the node like this: (end - start). This is all fine if end is pointing to the first non-available byte. The problem is that the current x86_64 code sometimes treats it as the last present byte and sometimes as the first non-available byte. The result is that some configurations might lose a page at the end of the range. This patch tries to fix CONFIG_ACPI_NUMA, CONFIG_K8_NUMA and CONFIG_NUMA_EMU so they all treat the end variable as the first non-available byte. This is the same way as the single node code. The patch is boot tested on dual x86_64 hardware with the above configurations, but maybe the removed code is needed as some workaround? Signed-off-by: Magnus Damm <magnus@valinux.co.jp> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14[PATCH] x86_64: Optimize NUMA node hash functionEric Dumazet
Compute the highest possible value for memnode_shift, in order to reduce footprint of memnodemap[] to the minimum, thus making all users (phys_to_nid(), kfree()), more cache friendly. Before the patch : Node 0 MemBase 0000000000000000 Limit 00000001ffffffff Node 1 MemBase 0000000200000000 Limit 00000003ffffffff Using 23 for the hash shift. Max adder is 3ffffffff After the patch : Node 0 MemBase 0000000000000000 Limit 00000001ffffffff Node 1 MemBase 0000000200000000 Limit 00000003ffffffff Using 33 for the hash shift. In this case, only 2 bytes of memnodemap[] are used, instead of 2048 Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14[PATCH] x86_64: Replace swiotlb extern with includeAndi Kleen
Minor victory on the continuous quest against all stray extern. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14[PATCH] x86_64: Replace cpu_pda extern with includeAndi Kleen
Minor cleanup - remove obsolete extern Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14[PATCH] x86_64: Only use asm/sections.h to declare section symbolsAndi Kleen
Adding __initdata_* to asm-generic/sections.h Replaces a lot of open coded externs in arch/x86_64/* I had to change __bss_end to __bss_stop to match the other architectures. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-14[PATCH] x86_64: Unmap NULL during early bootupSiddha, Suresh B
We should zap the low mappings, as soon as possible, so that we can catch kernel bugs more effectively. Previously early boot had NULL mapped and didn't trap on NULL references. This patch introduces boot_level4_pgt, which will always have low identity addresses mapped. Druing boot, all the processors will use this as their level4 pgt. On BP, we will switch to init_level4_pgt as soon as we enter C code and zap the low mappings as soon as we are done with the usage of identity low mapped addresses. On AP's we will zap the low mappings as soon as we jump to C code. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Ashok Raj <ashok.raj@intel.com> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>