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

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

On 1/6/21 9:10 PM, Guo Dong via groups.io 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>

With one little comment below, I verified this method allows my system to 
boot.

Tested-by: Tom Lendacky <thomas.lendacky@amd.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,

Extraneous comma after rcx.

Thanks,
Tom

>       lea     rax, [setCodeSelectorLongJump]
> -    mov     [rsp], rax
> -    mov     [rsp+4], cx
> -    jmp     dword far [rsp]
> +    push    rax
> +    o64 retf
>   setCodeSelectorLongJump:
> -    add     rsp, 0x10
>       ret
>   
>   ;------------------------------------------------------------------------------
>