[U-Boot] [PATCH v4 1/2] armv8: Support loading 32-bit OS in AArch32 execution state
Huan Wang
alison.wang at nxp.com
Mon Jul 4 05:39:13 CEST 2016
> On 30.06.16 09:16, Huan Wang wrote:
> > Hi, Alex,
> >
> >>> Am 15.06.2016 um 05:04 schrieb Huan Wang <alison.wang at nxp.com>:
> >>>
> >>> Hi, Alex,
> >>>
> >>>>> On 06/08/2016 07:14 AM, Alison Wang wrote:
> >>>>> To support loading a 32-bit OS, the execution state will change
> >>>>> from
> >>>>> AArch64 to AArch32 when jumping to kernel.
> >>>>>
> >>>>> The architecture information will be got through checking FIT
> >>>>> image, then U-Boot will load 32-bit OS or 64-bit OS automatically.
> >>>>>
> >>>>> Signed-off-by: Ebony Zhu <ebony.zhu at nxp.com>
> >>>>> Signed-off-by: Alison Wang <alison.wang at nxp.com>
> >>>>> Signed-off-by: Chenhui Zhao <chenhui.zhao at nxp.com>
> >>>>> ---
> >>>>> Changes in v4:
> >>>>> - Correct config ARM64_SUPPORT_AARCH32.
> >>>>> - Omit arch and ftaddr arguments.
> >>>>> - Rename "xreg5" to "tmp".
> >>>>> - Use xxx_RES1 to combine all RES1 fields in xxx register.
> >>>>> - Use an immediate cmp directly.
> >>>>> - Use #ifdef for CONFIG_ARM64_SUPPORT_AARCH32.
> >>>>>
> >>>>> Changes in v3:
> >>>>> - Comments the functions and the arguments.
> >>>>> - Rename the real parameters.
> >>>>> - Use the macros instead of the magic values.
> >>>>> - Remove the redundant codes.
> >>>>> - Clean up all of the mess in boot_jump_linux().
> >>>>> - Add CONFIG_ARM64_SUPPORT_AARCH32 to detect for some ARM64 system
> >>>> doesn't support AArch32 state.
> >>>>>
> >>>>> Changes in v2:
> >>>>> - armv8_switch_to_el2_aarch32() is removed. armv8_switch_to_el2_m
> >>>>> is
> >>>> used
> >>>>> to switch to AArch64 EL2 or AArch32 Hyp.
> >>>>> - armv8_switch_to_el1_aarch32() is removed. armv8_switch_to_el1_m
> >>>>> is
> >>>> used
> >>>>> to switch to AArch64 EL1 or AArch32 SVC.
> >>>>>
> >>>>> arch/arm/Kconfig | 6 ++
> >>>>> arch/arm/cpu/armv8/start.S | 1 +
> >>>>> arch/arm/cpu/armv8/transition.S | 8 +-
> >>>>> arch/arm/include/asm/macro.h | 172
> >>>> ++++++++++++++++++++++++++++++----------
> >>>>> arch/arm/include/asm/system.h | 111 +++++++++++++++++++++++++-
> >>>>> arch/arm/lib/bootm.c | 19 ++++-
> >>>>> common/image-fit.c | 19 ++++-
> >>>>> 7 files changed, 284 insertions(+), 52 deletions(-)
> >>>>>
> >>>>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index
> >>>>> 77eab66..9cf4acd 100644
> >>>>> --- a/arch/arm/Kconfig
> >>>>> +++ b/arch/arm/Kconfig
> >>>>> @@ -91,6 +91,12 @@ config SYS_L2CACHE_OFF
> >>>>> If SoC does not support L2CACHE or one do not want to
> enable
> >>>>> L2CACHE, choose this option.
> >>>>>
> >>>>> +config ARM64_SUPPORT_AARCH32
> >>>>> + bool "ARM64 system support AArch32 execution state"
> >>>>> + default y if ARM64 && !TARGET_THUNDERX_88XX
> >>>>> + help
> >>>>> + This ARM64 system supports AArch32 execution state.
> >>>>> +
> >>>>> choice
> >>>>> prompt "Target select"
> >>>>> default TARGET_HIKEY
> >>>>> diff --git a/arch/arm/cpu/armv8/start.S
> >>>>> b/arch/arm/cpu/armv8/start.S index e933021..dd69501 100644
> >>>>> --- a/arch/arm/cpu/armv8/start.S
> >>>>> +++ b/arch/arm/cpu/armv8/start.S
> >>>>> @@ -234,6 +234,7 @@ WEAK(lowlevel_init)
> >>>>> /*
> >>>>> * All slaves will enter EL2 and optionally EL1.
> >>>>> */
> >>>>> + ldr x3, =ES_TO_AARCH64
> >>>>> bl armv8_switch_to_el2
> >>>>> #ifdef CONFIG_ARMV8_SWITCH_TO_EL1
> >>>>> bl armv8_switch_to_el1
> >>>>> diff --git a/arch/arm/cpu/armv8/transition.S
> >>>> b/arch/arm/cpu/armv8/transition.S
> >>>>> index 253a39b..e61b6ae 100644
> >>>>> --- a/arch/arm/cpu/armv8/transition.S
> >>>>> +++ b/arch/arm/cpu/armv8/transition.S
> >>>>> @@ -11,13 +11,13 @@
> >>>>> #include <asm/macro.h>
> >>>>>
> >>>>> ENTRY(armv8_switch_to_el2)
> >>>>> - switch_el x0, 1f, 0f, 0f
> >>>>> + switch_el x4, 1f, 0f, 0f
> >>>>> 0: ret
> >>>>> -1: armv8_switch_to_el2_m x0
> >>>>> +1: armv8_switch_to_el2_m x0, x3, x4
> >>>>> ENDPROC(armv8_switch_to_el2)
> >>>>>
> >>>>> ENTRY(armv8_switch_to_el1)
> >>>>> - switch_el x0, 0f, 1f, 0f
> >>>>> + switch_el x4, 0f, 1f, 0f
> >>>>> 0: ret
> >>>>> -1: armv8_switch_to_el1_m x0, x1
> >>>>> +1: armv8_switch_to_el1_m x0, x3, x4
> >>>>> ENDPROC(armv8_switch_to_el1)
> >>>>> diff --git a/arch/arm/include/asm/macro.h
> >>>> b/arch/arm/include/asm/macro.h
> >>>>> index 9bb0efa..109724f 100644
> >>>>> --- a/arch/arm/include/asm/macro.h
> >>>>> +++ b/arch/arm/include/asm/macro.h
> >>>>> @@ -8,6 +8,9 @@
> >>>>>
> >>>>> #ifndef __ASM_ARM_MACRO_H__
> >>>>> #define __ASM_ARM_MACRO_H__
> >>>>> +
> >>>>> +#include <asm/system.h>
> >>>>> +
> >>>>> #ifdef __ASSEMBLY__
> >>>>>
> >>>>> /*
> >>>>> @@ -135,13 +138,20 @@ lr .req x30
> >>>>> #endif
> >>>>> .endm
> >>>>>
> >>>>> -.macro armv8_switch_to_el2_m, xreg1
> >>>>> - /* 64bit EL2 | HCE | SMD | RES1 (Bits[5:4]) | Non-secure
> >> EL0/EL1
> >>>> */
> >>>>> - mov \xreg1, #0x5b1
> >>>>> - msr scr_el3, \xreg1
> >>>>> +/*
> >>>>> + * Switch from EL3 to EL2 for ARMv8
> >>>>> + * @ep: kernel entry point
> >>>>> + * @flag: The execution state flag for lower exception
> >>>>> + * level, ES_TO_AARCH64 or ES_TO_AARCH32
> >>>>> + * @tmp: temporary register
> >>>>> + *
> >>>>> + * x1 is machine nr and x2 is ftaddr, they will be passed
> >>>>> + * to the guest.
> >>>>> + */
> >>>>> +.macro armv8_switch_to_el2_m, ep, flag, tmp
> >>>>> msr cptr_el3, xzr /* Disable coprocessor traps to
> EL3
> >>>> */
> >>>>> - mov \xreg1, #0x33ff
> >>>>> - msr cptr_el2, \xreg1 /* Disable coprocessor traps to
> EL2
> >> */
> >>>>> + mov \tmp, #CPTR_EL2_RES1
> >>>>> + msr cptr_el2, \tmp /* Disable coprocessor traps to
> >> EL2
> >>>> */
> >>>>>
> >>>>> /* Initialize Generic Timers */
> >>>>> msr cntvoff_el2, xzr
> >>>>> @@ -152,45 +162,91 @@ lr .req x30
> >>>>> * and RES0 bits (31,30,27,26,24,21,20,17,15-13,10-6) +
> >>>>> * EE,WXN,I,SA,C,A,M to 0
> >>>>> */
> >>>>> - mov \xreg1, #0x0830
> >>>>> - movk \xreg1, #0x30C5, lsl #16
> >>>>> - msr sctlr_el2, \xreg1
> >>>>> + ldr \tmp, =(SCTLR_EL2_RES1 | SCTLR_EL2_EE_LE |\
> >>>>> + SCTLR_EL2_WXN_DIS | SCTLR_EL2_ICACHE_DIS |\
> >>>>> + SCTLR_EL2_SA_DIS | SCTLR_EL2_DCACHE_DIS |\
> >>>>> + SCTLR_EL2_ALIGN_DIS | SCTLR_EL2_MMU_DIS)
> >>>>> + msr sctlr_el2, \tmp
> >>>>> +
> >>>>> + mov \tmp, sp
> >>>>> + msr sp_el2, \tmp /* Migrate SP */
> >>>>> + mrs \tmp, vbar_el3
> >>>>> + msr vbar_el2, \tmp /* Migrate VBAR */
> >>>>> +
> >>>>> + /* Check switch to AArch64 EL2 or AArch32 Hypervisor mode */
> >>>>> + cmp \flag, #ES_TO_AARCH32
> >>>>> + b.eq 1f
> >>>>> +
> >>>>> + /*
> >>>>> + * The next lower exception level is AArch64, 64bit EL2 | HCE
> |
> >>>>> + * SMD | RES1 (Bits[5:4]) | Non-secure EL0/EL1.
> >>>>> + */
> >>>>> + ldr \tmp, =(SCR_EL3_RW_AARCH64 | SCR_EL3_HCE_EN |\
> >>>>> + SCR_EL3_SMD_DIS | SCR_EL3_RES1 |\
> >>>>> + SCR_EL3_NS_EN)
> >>>>> + msr scr_el3, \tmp
> >>>>>
> >>>>> /* Return to the EL2_SP2 mode from EL3 */
> >>>>> - mov \xreg1, sp
> >>>>> - msr sp_el2, \xreg1 /* Migrate SP */
> >>>>> - mrs \xreg1, vbar_el3
> >>>>> - msr vbar_el2, \xreg1 /* Migrate VBAR */
> >>>>> - mov \xreg1, #0x3c9
> >>>>> - msr spsr_el3, \xreg1 /* EL2_SP2 | D | A | I | F */
> >>>>> + ldr \tmp, =(SPSR_EL_DEBUG_MASK | SPSR_EL_SERR_MASK |\
> >>>>> + SPSR_EL_IRQ_MASK | SPSR_EL_FIQ_MASK |\
> >>>>> + SPSR_EL_M_AARCH64 | SPSR_EL_M_EL2H)
> >>>>> + msr spsr_el3, \tmp
> >>>>> msr elr_el3, lr
> >>>>
> >>>> So if we switch into AArch64 mode, we return ...
> >>>>
> >>>>> eret
> >>>>> +
> >>>>> +1:
> >>>>> + /*
> >>>>> + * The next lower exception level is AArch32, 32bit EL2 | HCE
> |
> >>>>> + * SMD | RES1 (Bits[5:4]) | Non-secure EL0/EL1.
> >>>>> + */
> >>>>> + ldr \tmp, =(SCR_EL3_RW_AARCH32 | SCR_EL3_HCE_EN |\
> >>>>> + SCR_EL3_SMD_DIS | SCR_EL3_RES1 |\
> >>>>> + SCR_EL3_NS_EN)
> >>>>> + msr scr_el3, \tmp
> >>>>> +
> >>>>> + /* Return to AArch32 Hypervisor mode */
> >>>>> + ldr \tmp, =(SPSR_EL_END_LE | SPSR_EL_ASYN_MASK |\
> >>>>> + SPSR_EL_IRQ_MASK | SPSR_EL_FIQ_MASK |\
> >>>>> + SPSR_EL_T_A32 | SPSR_EL_M_AARCH32 |\
> >>>>> + SPSR_EL_M_HYP)
> >>>>> + msr spsr_el3, \tmp
> >>>>> + msr elr_el3, \ep
> >>>>> +
> >>>>> + mov \ep, #0
> >>>>
> >>>> ... while if we switch to AArch32 mode we jump to ep.
> >>>>
> >>>> I think it would make a lot of sense if we could *always* jump to
> ep.
> >>>> Just swizzle the argument order so that you get
> >>>>
> >>>> if ((IH_ARCH_DEFAULT == IH_ARCH_ARM64) &&
> >>>> (images->os.arch == IH_ARCH_ARM))
> >>>> armv8_switch_to_el2(0,
> >>>> gd->bd->bi_arch_number, (uintptr_t)images->ft_addr, (u64)images->ep,
> ES_TO_AARCH32);
> >>>> else
> >>>> armv8_switch_to_el2((uintptr_t)images->ft_addr, 0 0, images->ep,
> >>>> ES_TO_AARCH64);
> >>> [Alison Wang] I don't agree it would make a lot of sense if we could
> >>> *always* jump to ep.
> >>> If we switch to EL2 AArch32 mode, it will happen at the last minute
> >>> from U-Boot to kernel. The ep is the entry pointer for kernel.
> >>> If we switch to EL2 AArch64 mode, it will happen earlier. For
> >>> primary core, it will call kernel entry after the switch. For
> >>> secondary cores, it will switch from EL3 AArch64 to EL2 AArch64
> >>> first, then it will wait until the spin-table is written by the
> >>> kernel, later it will jump
> >> to kernel.
> >>
> >> Then jump to a separate function that continues the execution stream.
> >> I really think we should keep the interface between both flags as
> >> identical as possible.
> > [Alison Wang] I think you are right. I will change the code to
> > *always* jump to ep in v5.
> >>
> >>>>
> >>>> If you *really really really* are attached to booting into EL1,
> >>>> just add a small function that calls armv8_switch_to_el1() for you
> >>>> and pass the pointer to that as ep to the el2 switch. If I were you
> >>>> I'd just remove the EL1 mess.
> >>> [Alison Wang] I agreed with you to remove the EL1 mess.
> >>
> >> Awesome, thanks.
> > [Alison Wang] When I tried to remove the EL1 mess, I found
> > CONFIG_ARMV8_SWITCH_TO_EL1 is enabled for Versatile Express Aemv8a. If
> > that platform uses it, I have a concern about removing it.
>
> Do you have access to the respective simulator? It's probably only
> enabled because in the very very very early days of Linux bringup Linux
> didn't know how to run in EL2 yet. So we can probably just drop it.
>
> But let's CC people who might know :).
>
[Alison Wang] Alex, thanks for the explanation.
Does anyone disagree to remove CONFIG_ARMV8_SWITCH_TO_EL1 and other corresponding functions?
If there is no disagreement, I will remove them in the v5 patches.
Best Regards,
Alison Wang
More information about the U-Boot
mailing list