[U-Boot] [PATCH v4 1/2] armv8: Support loading 32-bit OS in AArch32 execution state
Huan Wang
alison.wang at nxp.com
Thu Jun 30 09:16:12 CEST 2016
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.
Best Regards,
Alison Wang
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