€•ÿ+      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ1/translations/zh_CN/arch/x86/x86_64/5level-paging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ1/translations/zh_TW/arch/x86/x86_64/5level-paging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ1/translations/it_IT/arch/x86/x86_64/5level-paging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ1/translations/ja_JP/arch/x86/x86_64/5level-paging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ1/translations/ko_KR/arch/x86/x86_64/5level-paging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ1/translations/sp_SP/arch/x86/x86_64/5level-paging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒK/var/lib/git/docbuild/linux/Documentation/arch/x86/x86_64/5level-paging.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒ5-level paging”h]”hŒ5-level paging”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒOverview”h]”hŒOverview”…””}”(hhÌhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hhÉhžhhŸh³h KubhŒ	paragraph”“”)”}”(hŒ×Original x86-64 was limited by 4-level paging to 256 TiB of virtual address
space and 64 TiB of physical address space. We are already bumping into
this limit: some vendors offer servers with 64 TiB of memory today.”h]”hŒ×Original x86-64 was limited by 4-level paging to 256 TiB of virtual address
space and 64 TiB of physical address space. We are already bumping into
this limit: some vendors offer servers with 64 TiB of memory today.”…””}”(hhÜhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K	hhÉhžhubhÛ)”}”(hŒÄTo overcome the limitation upcoming hardware will introduce support for
5-level paging. It is a straight-forward extension of the current page
table structure adding one more layer of translation.”h]”hŒÄTo overcome the limitation upcoming hardware will introduce support for
5-level paging. It is a straight-forward extension of the current page
table structure adding one more layer of translation.”…””}”(hhêhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhÉhžhubhÛ)”}”(hŒ†It bumps the limits to 128 PiB of virtual address space and 4 PiB of
physical address space. This "ought to be enough for anybody" Â©.”h]”hŒŠIt bumps the limits to 128 PiB of virtual address space and 4 PiB of
physical address space. This â€œought to be enough for anybodyâ€ Â©.”…””}”(hhøhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhÉhžhubhÛ)”}”(hŒ*QEMU 2.9 and later support 5-level paging.”h]”hŒ*QEMU 2.9 and later support 5-level paging.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhÉhžhubhÛ)”}”(hŒ]Virtual memory layout for 5-level paging is described in
Documentation/arch/x86/x86_64/mm.rst”h]”hŒ]Virtual memory layout for 5-level paging is described in
Documentation/arch/x86/x86_64/mm.rst”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhÉhžhubeh}”(h]”Œoverview”ah ]”h"]”Œoverview”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒEnabling 5-level paging”h]”hŒEnabling 5-level paging”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj*  hžhhŸh³h KubhÛ)”}”(hŒ(CONFIG_X86_5LEVEL=y enables the feature.”h]”hŒ(CONFIG_X86_5LEVEL=y enables the feature.”…””}”(hj;  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Khj*  hžhubhÛ)”}”(hŒ•Kernel with CONFIG_X86_5LEVEL=y still able to boot on 4-level hardware.
In this case additional page table level -- p4d -- will be folded at
runtime.”h]”hŒ•Kernel with CONFIG_X86_5LEVEL=y still able to boot on 4-level hardware.
In this case additional page table level -- p4d -- will be folded at
runtime.”…””}”(hjI  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Khj*  hžhubeh}”(h]”Œenabling-5-level-paging”ah ]”h"]”Œenabling 5-level paging”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒ*User-space and large virtual address space”h]”hŒ*User-space and large virtual address space”…””}”(hjb  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj_  hžhhŸh³h K#ubhÛ)”}”(hX+  On x86, 5-level paging enables 56-bit userspace virtual address space.
Not all user space is ready to handle wide addresses. It's known that
at least some JIT compilers use higher bits in pointers to encode their
information. It collides with valid pointers with 5-level paging and
leads to crashes.”h]”hX-  On x86, 5-level paging enables 56-bit userspace virtual address space.
Not all user space is ready to handle wide addresses. Itâ€™s known that
at least some JIT compilers use higher bits in pointers to encode their
information. It collides with valid pointers with 5-level paging and
leads to crashes.”…””}”(hjp  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K$hj_  hžhubhÛ)”}”(hŒ]To mitigate this, we are not going to allocate virtual address space
above 47-bit by default.”h]”hŒ]To mitigate this, we are not going to allocate virtual address space
above 47-bit by default.”…””}”(hj~  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K*hj_  hžhubhÛ)”}”(hŒ‚But userspace can ask for allocation from full address space by
specifying hint address (with or without MAP_FIXED) above 47-bits.”h]”hŒ‚But userspace can ask for allocation from full address space by
specifying hint address (with or without MAP_FIXED) above 47-bits.”…””}”(hjŒ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K-hj_  hžhubhÛ)”}”(hŒåIf hint address set above 47-bit, but MAP_FIXED is not specified, we try
to look for unmapped area by specified address. If it's already
occupied, we look for unmapped area in *full* address space, rather than
from 47-bit window.”h]”(hŒ²If hint address set above 47-bit, but MAP_FIXED is not specified, we try
to look for unmapped area by specified address. If itâ€™s already
occupied, we look for unmapped area in ”…””}”(hjš  hžhhŸNh NubhŒemphasis”“”)”}”(hŒ*full*”h]”hŒfull”…””}”(hj¤  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j¢  hjš  ubhŒ/ address space, rather than
from 47-bit window.”…””}”(hjš  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K0hj_  hžhubhÛ)”}”(hŒ]A high hint address would only affect the allocation in question, but not
any future mmap()s.”h]”hŒ]A high hint address would only affect the allocation in question, but not
any future mmap()s.”…””}”(hj¼  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K5hj_  hžhubhÛ)”}”(hŒ¾Specifying high hint address on older kernel or on machine without 5-level
paging support is safe. The hint will be ignored and kernel will fall back
to allocation from 47-bit address space.”h]”hŒ¾Specifying high hint address on older kernel or on machine without 5-level
paging support is safe. The hint will be ignored and kernel will fall back
to allocation from 47-bit address space.”…””}”(hjÊ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K8hj_  hžhubhÛ)”}”(hŒœThis approach helps to easily make application's memory allocator aware
about large address space without manually tracking allocated virtual
address space.”h]”hŒžThis approach helps to easily make applicationâ€™s memory allocator aware
about large address space without manually tracking allocated virtual
address space.”…””}”(hjØ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K<hj_  hžhubhÛ)”}”(hX  One important case we need to handle here is interaction with MPX.
MPX (without MAWA extension) cannot handle addresses above 47-bit, so we
need to make sure that MPX cannot be enabled we already have VMA above
the boundary and forbid creating such VMAs once MPX is enabled.”h]”hX  One important case we need to handle here is interaction with MPX.
MPX (without MAWA extension) cannot handle addresses above 47-bit, so we
need to make sure that MPX cannot be enabled we already have VMA above
the boundary and forbid creating such VMAs once MPX is enabled.”…””}”(hjæ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K@hj_  hžhubeh}”(h]”Œ*user-space-and-large-virtual-address-space”ah ]”h"]”Œ*user-space and large virtual address space”ah$]”h&]”uh1h´hh¶hžhhŸh³h K#ubeh}”(h]”Œlevel-paging”ah ]”h"]”Œ5-level paging”ah$]”h&]”uh1h´hhhžhhŸh³h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h³uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¹NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j'  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h³Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j  jþ  j'  j$  j\  jY  jù  jö  uŒ	nametypes”}”(j  ‰j'  ‰j\  ‰jù  ‰uh}”(jþ  h¶j$  hÉjY  j*  jö  j_  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.