arch/arm64/booting.rst

13 (EL0 - EL3), with EL0, EL1 and EL2 having a secure and a non-secure
17 For the purposes of this document, we will use the term `boot loader`
20 hypervisor code, or it may just be a handful of instructions for
26 1. Setup and initialise the RAM
32 1. Setup and initialise RAM
33 ---------------------------
37 The boot loader is expected to find and initialise all RAM that the
38 kernel will use for volatile data storage in the system.  It performs
39 this in a machine dependent manner.  (It may use internal algorithms
40 to automatically locate and size all RAM, or it may use knowledge of
41 the RAM in the machine, or any other method the boot loader designer
46 -------------------------
50 The device tree blob (dtb) must be placed on an 8-byte boundary and must
59 ------------------------------
71 ------------------------
75 The decompressed kernel image contains a 64-byte header as follows::
77   u32 code0;			/* Executable code */
78   u32 code1;			/* Executable code */
91 - As of v3.17, all fields are little endian unless stated otherwise.
93 - code0/code1 are responsible for branching to stext.
95 - when booting through EFI, code0/code1 are initially skipped.
100 - Prior to v3.17, the endianness of text_offset was not specified.  In
102   endianness of the kernel.  Where image_size is non-zero image_size is
103   little-endian and must be respected.  Where image_size is zero,
106 - The flags field (introduced in v3.17) is a little-endian 64-bit field
111   Bit 1-2	Kernel Page size.
113 			* 0 - Unspecified.
114 			* 1 - 4K
115 			* 2 - 16K
116 			* 3 - 64K
126 			  the 48-bit addressable range of physical memory
127   Bits 4-63	Reserved.
130 - When image_size is zero, a bootloader should attempt to keep as much
131   memory as possible free for use by the kernel immediately after the
136 address anywhere in usable system RAM and called there. The region
140 use by the kernel.
141 NOTE: versions prior to v4.6 cannot make use of memory below the
143 placed as close as possible to the start of system RAM.
156 - Quiesce all DMA capable devices so that memory does not get
160 - Primary CPU general-purpose register settings:
162     - x0 = physical address of device tree blob (dtb) in system RAM.
163     - x1 = 0 (reserved for future use)
164     - x2 = 0 (reserved for future use)
165     - x3 = 0 (reserved for future use)
167 - CPU mode
171   The CPU must be in non-secure state, either in EL2 (RECOMMENDED in order
174 - Caches, MMUs
190 - Architected timers
197 - Coherency
204 - System registers
212   - If EL3 is present:
214     - SCR_EL3.FIQ must have the same value across all CPUs the kernel is
216     - The value of SCR_EL3.FIQ must be the same as the one present at boot
219   - If EL3 is present and the kernel is entered at EL2:
221     - SCR_EL3.HCE (bit 8) must be initialised to 0b1.
224   - If EL3 is present:
226       - ICC_SRE_EL3.Enable (bit 3) must be initialised to 0b1.
227       - ICC_SRE_EL3.SRE (bit 0) must be initialised to 0b1.
228       - ICC_CTLR_EL3.PMHE (bit 6) must be set to the same value across
232   - If the kernel is entered at EL1:
234       - ICC.SRE_EL2.Enable (bit 3) must be initialised to 0b1
235       - ICC_SRE_EL2.SRE (bit 0) must be initialised to 0b1.
237   - The DT or ACPI tables must describe a GICv3 interrupt controller.
242   - If EL3 is present:
246   - If the kernel is entered at EL1:
250   - The DT or ACPI tables must describe a GICv2 interrupt controller.
254   - If EL3 is present:
256     - SCR_EL3.APK (bit 16) must be initialised to 0b1
257     - SCR_EL3.API (bit 17) must be initialised to 0b1
259   - If the kernel is entered at EL1:
261     - HCR_EL2.APK (bit 40) must be initialised to 0b1
262     - HCR_EL2.API (bit 41) must be initialised to 0b1
266   - If EL3 is present:
268     - CPTR_EL3.TAM (bit 30) must be initialised to 0b0
269     - CPTR_EL2.TAM (bit 30) must be initialised to 0b0
270     - AMCNTENSET0_EL0 must be initialised to 0b1111
271     - AMCNTENSET1_EL0 must be initialised to a platform specific value
275   - If the kernel is entered at EL1:
277     - AMCNTENSET0_EL0 must be initialised to 0b1111
278     - AMCNTENSET1_EL0 must be initialised to a platform specific value
284   - If EL3 is present and the kernel is entered at EL2:
286     - SCR_EL3.FGTEn (bit 27) must be initialised to 0b1.
290   - If EL3 is present and the kernel is entered at EL2:
292     - SCR_EL3.HXEn (bit 38) must be initialised to 0b1.
296   - If EL3 is present:
298     - CPTR_EL3.TFP (bit 10) must be initialised to 0b0.
300   - If EL2 is present and the kernel is entered at EL1:
302     - CPTR_EL2.TFP (bit 10) must be initialised to 0b0.
306   - if EL3 is present:
308     - CPTR_EL3.EZ (bit 8) must be initialised to 0b1.
310     - ZCR_EL3.LEN must be initialised to the same value for all CPUs the
313   - If the kernel is entered at EL1 and EL2 is present:
315     - CPTR_EL2.TZ (bit 8) must be initialised to 0b0.
317     - CPTR_EL2.ZEN (bits 17:16) must be initialised to 0b11.
319     - ZCR_EL2.LEN must be initialised to the same value for all CPUs the
324   - If EL3 is present:
326     - CPTR_EL3.ESM (bit 12) must be initialised to 0b1.
328     - SCR_EL3.EnTP2 (bit 41) must be initialised to 0b1.
330     - SMCR_EL3.LEN must be initialised to the same value for all CPUs the
333  - If the kernel is entered at EL1 and EL2 is present:
335     - CPTR_EL2.TSM (bit 12) must be initialised to 0b0.
337     - CPTR_EL2.SMEN (bits 25:24) must be initialised to 0b11.
339     - SCTLR_EL2.EnTP2 (bit 60) must be initialised to 0b1.
341     - SMCR_EL2.LEN must be initialised to the same value for all CPUs the
344     - HWFGRTR_EL2.nTPIDR2_EL0 (bit 55) must be initialised to 0b01.
346     - HWFGWTR_EL2.nTPIDR2_EL0 (bit 55) must be initialised to 0b01.
348     - HWFGRTR_EL2.nSMPRI_EL1 (bit 54) must be initialised to 0b01.
350     - HWFGWTR_EL2.nSMPRI_EL1 (bit 54) must be initialised to 0b01.
354   - If EL3 is present:
356     - SMCR_EL3.FA64 (bit 31) must be initialised to 0b1.
358  - If the kernel is entered at EL1 and EL2 is present:
360     - SMCR_EL2.FA64 (bit 31) must be initialised to 0b1.
364   - If EL3 is present:
366     - SCR_EL3.ATA (bit 26) must be initialised to 0b1.
368   - If the kernel is entered at EL1 and EL2 is present:
370     - HCR_EL2.ATA (bit 56) must be initialised to 0b1.
374   - If EL3 is present:
376     - SMCR_EL3.EZT0 (bit 30) must be initialised to 0b1.
378  - If the kernel is entered at EL1 and EL2 is present:
380     - SMCR_EL2.EZT0 (bit 30) must be initialised to 0b1.
384   - If the kernel is entered at EL1 and EL2 is present:
386     - HCRX_EL2.MSCEn (bit 11) must be initialised to 0b1.
390   - If EL3 is present:
392     - SCR_EL3.TCR2En (bit 43) must be initialised to 0b1.
394  - If the kernel is entered at EL1 and EL2 is present:
396     - HCRX_EL2.TCR2En (bit 14) must be initialised to 0b1.
400   - If EL3 is present:
402     - SCR_EL3.PIEn (bit 45) must be initialised to 0b1.
404   - If the kernel is entered at EL1 and EL2 is present:
406     - HFGRTR_EL2.nPIR_EL1 (bit 58) must be initialised to 0b1.
408     - HFGWTR_EL2.nPIR_EL1 (bit 58) must be initialised to 0b1.
410     - HFGRTR_EL2.nPIRE0_EL1 (bit 57) must be initialised to 0b1.
412     - HFGRWR_EL2.nPIRE0_EL1 (bit 57) must be initialised to 0b1.
424 - The primary CPU must jump directly to the first instruction of the
426   an 'enable-method' property for each cpu node.  The supported
427   enable-methods are described below.
432 - CPUs with a "spin-table" enable-method must have a 'cpu-release-addr'
434   naturally-aligned 64-bit zero-initalised memory location.
438   device tree) polling their cpu-release-addr location, which must be
440   to reduce the overhead of the busy-loop and a sev will be issued by
442   cpu-release-addr returns a non-zero value, the CPU must jump to this
443   value.  The value will be written as a single 64-bit little-endian
447 - CPUs with a "psci" enable method should remain outside of
458 - Secondary CPU general-purpose register settings
460   - x0 = 0 (reserved for future use)
461   - x1 = 0 (reserved for future use)
462   - x2 = 0 (reserved for future use)
463   - x3 = 0 (reserved for future use)