Re: [edk2-devel] [PATCH V2] UefiCpuPkg/CpuDxe: Fix boot error

["Laszlo Ersek" <lersek@redhat.com>]

Adding James, Mike, and Tom:

On 01/07/21 04:10, Guo Dong wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3084
> 
> When DXE drivers are dispatched above 4GB memory in 64bit
> mode, the address setCodeSelectorLongJump in stack will
> be override by parameter. Jump to Qword is not supported
> by some processors. So use "o64 retf" instead.
> 
> Signed-off-by: Guo Dong <guo.dong@intel.com>
> ---
>  UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm b/UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm
> index c3489bcc3e..a8216cd56f 100644
> --- a/UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm
> +++ b/UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm
> @@ -20,13 +20,11 @@
>  ;------------------------------------------------------------------------------
>  global ASM_PFX(SetCodeSelector)
>  ASM_PFX(SetCodeSelector):
> -    sub     rsp, 0x10
> +    push    rcx,
>      lea     rax, [setCodeSelectorLongJump]
> -    mov     [rsp], rax
> -    mov     [rsp+4], cx
> -    jmp     dword far [rsp]
> +    push    rax
> +    o64 retf
>  setCodeSelectorLongJump:
> -    add     rsp, 0x10
>      ret
>  
>  ;------------------------------------------------------------------------------
> 

I'm asking for:

- a Reviewed-by or Tested-by from James please, and
- an Acked-by or Reviewed-by from Mike please, and
- a Reviewed-by or Tested-by from Tom please.

Personally I'm not going to verify the details of the conversion of the
mode switch, from the far jump to the far ret, but squinting from a
distance, the patch looks plausible.

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks!
Laszlo