linux.git/arch/xtensa/kernel/head.S, branch v7.1

arch, mm: consolidate empty_zero_page

2026-04-05T20:53:01+00:00

Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of
ZERO_PAGE() to 4.

Every architecture defines empty_zero_page that way or another, but for the
most of them it is always a page aligned page in BSS and most definitions
of ZERO_PAGE do virt_to_page(empty_zero_page).

Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the
core MM and drop these definitions in architectures that do not implement
colored zero page (MIPS and s390).

ZERO_PAGE() remains a macro because turning it to a wrapper for a static
inline causes severe pain in header dependencies.

For the most part the change is mechanical, with these being noteworthy:

* alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot
  parameters. Switching to a generic empty_zero_page removes the aliasing
  and keeps ZERO_PGE for boot parameters only
* arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of
  ZERO_PAGE() is kept intact.
* m68k/parisc/um: allocated empty_zero_page from memblock,
  although they do not support zero page coloring and having it in BSS
  will work fine.
* sparc64 can have empty_zero_page in BSS rather allocate it, but it
  can't use virt_to_page() for BSS. Keep it's definition of ZERO_PAGE()
  but instead of allocating it, make mem_map_zero point to
  empty_zero_page.
* sh: used empty_zero_page for boot parameters at the very early boot.
  Rename the parameters page to boot_params_page and let sh use the generic
  empty_zero_page.
* hexagon: had an amusing comment about empty_zero_page

	/* A handy thing to have if one has the RAM. Declared in head.S */

  that unfortunately had to go :)

Link: https://lkml.kernel.org/r/20260211103141.3215197-4-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) 
Acked-by: Helge Deller 		[parisc]
Tested-by: Helge Deller 		[parisc]
Reviewed-by: Christophe Leroy (CS GROUP) 
Acked-by: Dave Hansen 
Acked-by: Catalin Marinas 
Acked-by: Magnus Lindholm 	[alpha]
Acked-by: Dinh Nguyen 	[nios2]
Acked-by: Andreas Larsson 	[sparc]
Acked-by: David Hildenbrand (Arm) 
Acked-by: Liam R. Howlett 
Cc: "Borislav Petkov (AMD)" 
Cc: David S. Miller 
Cc: Geert Uytterhoeven 
Cc: Guo Ren 
Cc: Huacai Chen 
Cc: Ingo Molnar 
Cc: Johannes Berg 
Cc: John Paul Adrian Glaubitz 
Cc: Lorenzo Stoakes 
Cc: Madhavan Srinivasan 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Hocko 
Cc: Michal Simek 
Cc: Palmer Dabbelt 
Cc: Richard Weinberger 
Cc: Russell King 
Cc: Stafford Horne 
Cc: Suren Baghdasaryan 
Cc: Vineet Gupta 
Cc: Vlastimil Babka 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

xtensa: use register window specific opcodes only when present

2021-10-19T05:19:35+00:00

xtensa core may be configured without register windows support, don't
use register window specific opcodes in that case. Use window register
specific opcodes to initialize hardware or reset core to a known state
regardless of the chosen ABI.

Signed-off-by: Max Filippov

xtensa: implement call0 ABI support in assembly

2021-10-19T05:19:35+00:00

Replace hardcoded register and opcode names with ABI-agnostic macros.
Add register save/restore code where necessary. Conditionalize windowed
only or call0 only code. Add stack initialization matching _switch_to
epilogue to copy_thread.

Signed-off-by: Max Filippov

xtensa: Couple of typo fixes

2021-04-04T22:39:04+00:00

s/contans/contains/
s/desination/destination/

Signed-off-by: Bhaskar Chowdhury 
Message-Id: <20210325040832.26018-1-unixbhaskar@gmail.com>
Signed-off-by: Max Filippov

xtensa: add XIP kernel support

2019-11-26T19:33:38+00:00

XIP (eXecute In Place) kernel image is the image that can be run
directly from ROM, using RAM only for writable data.

XIP xtensa kernel differs from regular xtensa kernel in the following
ways:
- it has exception/IRQ vectors merged into text section. No vectors
  relocation takes place at kernel startup.
- .data/.bss location must be specified in the kernel configuration,
  its content is copied there in the _startup function.
- .init.text is merged with the rest of text and is executed from ROM.
- when MMU is used the virtual address where the kernel will be mapped
  must be specified in the kernel configuration. It may be in the KSEG
  or in the KIO, __pa macro is adjusted to be able to handle both.

Signed-off-by: Max Filippov

xtensa: fix section name for start_info

2019-10-21T06:48:29+00:00

.data.init.refok has been removed from the kernel long ago, replaced
with __REFDATA. Fix start_info definition.

Signed-off-by: Max Filippov

xtensa: clean up PS_WOE_BIT usage

2019-09-01T20:11:57+00:00

PS_WOE_BIT is mainly used to generate PS.WOE mask in the code. Introduce
PS_WOE_MASK macro and use it instead.

Signed-off-by: Max Filippov

xtensa: SMP: fix secondary CPU initialization

2019-01-26T10:02:13+00:00

- add missing memory barriers to the secondary CPU synchronization spin
  loops; add comment to the matching memory barrier in the boot_secondary
  and __cpu_die functions;
- use READ_ONCE/WRITE_ONCE to access cpu_start_id/cpu_start_ccount
  instead of reading/writing them directly;
- re-initialize cpu_running every time before starting secondary CPU to
  flush possible previous CPU startup results.

Signed-off-by: Max Filippov

xtensa: don't use l32r opcode directly

2018-12-05T20:53:07+00:00

xtensa assembler is capable of representing register loads with either
movi + addmi, l32r or const16, depending on the core configuration.
Don't use '.literal' and 'l32r' directly in the code, use 'movi' and let
the assembler relax them.

Signed-off-by: Max Filippov

xtensa: fix boot parameters address translation

2018-11-14T08:15:32+00:00

The bootloader may pass physical address of the boot parameters structure
to the MMUv3 kernel in the register a2. Code in the _SetupMMU block in
the arch/xtensa/kernel/head.S is supposed to map that physical address to
the virtual address in the configured virtual memory layout.

This code haven't been updated when additional 256+256 and 512+512
memory layouts were introduced and it may produce wrong addresses when
used with these layouts.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov