Hi, sharma:
Thanks for your answer!
I described my understanding on current ARM UEFI code:
1. Most ARM UEFI code package is based on ARMv7 SOCs.
Because of lacking ARMv8 development board, so enthusiast ported uefi code
on 32bit SOC.
2. ARMv8 supports aarch32 state.
So, if ARMv8 SOC powered to aarch32 state:
Developer could use current 32bit uefi code as code base to boot to uefi
shell environment.
3. at uefi shell environment, there are 2 methods to boot 64bit linux kernel.
(1) switch to aarch64 state, then boot to linux kernel's entry point.
(2) linux kernel's entry point included code to switch itself's execute
state to aarch64.if this assumption exist, uefi bootloader just keep aarch32
state.
Best wishes,
-----邮件原件-----
发件人: [email protected] [mailto:[email protected]]
发送时间: 2014年1月13日 11:26
收件人: '[email protected]'
抄送: '[email protected]'
主题: Re: [edk2] [edk2-ARM] ARMv8 bootloader question
Hi Tiger,
AFAIK, the AArch64 ISA is written from scratch for 64-bit support.
Although it is backward compatible with AArch32 and binaries compiled
for AArch32 (ARMv7 compatible) are supposed to run well on the ARMv8
machine running in AArch32 mode.
However, as per my understanding (and Olivier can correct me if I am wrong
here),
the UEFI code for ARMv8 executes in AArch64 mode - usually if the ARM core
boots up in AArch64 in EL3, bootloaders like UEFI/u-boot also execute in
AArch64 EL3
or EL2.
Regards,
Bhupesh
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> Sent: Monday, January 13, 2014 6:32 AM
> To: [email protected]
> Cc: [email protected]
> Subject: [edk2] [edk2-ARM] ARMv8 bootloader question
>
> Hi, Oliver:
> I have a question abourt ARMv8 CPU's bootloader.
> ARMv8 supports: AARCH32 / AARCH64
> Take an example:
> An ARMv8 SOC, when power up / reset, its default state is : AARCH32 Then,
> could i still run an old arm uefi bootloader which written by
> ARMv7 instruction set?
> I will switch ARMv8 SOC to AARCH64 before jumping into linux kernel.
> Is it possible?
>
> Best wishes,
>
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