linux-kernel - Re: [PATCH 1/5] x86/boot: Initialize boot

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Message-ID: <20201008134458.GA2429573@rani.riverdale.lan>
Date:   Thu, 8 Oct 2020 09:44:58 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] x86/boot: Initialize boot_params in startup code

On Thu, Oct 08, 2020 at 11:04:20AM +0200, Joerg Roedel wrote:
> On Wed, Oct 07, 2020 at 03:53:47PM -0400, Arvind Sankar wrote:
> > Save the boot_params pointer passed in by the bootloader in
> > startup_32/64. This avoids having to initialize it in two different
> > places in C code, and having to preserve SI through the early assembly
> > code.
> > 
> > Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
> 
> Nice cleanup!
> 
> >  /*
> >   * Jump to the extracted kernel.
> >   */
> > -	xorl	%ebx, %ebx
> > +	movl	boot_params@...OFF(%ebx), %esi
> >  	jmp	*%eax
> >  SYM_FUNC_END(.Lrelocated)
> >  
> > @@ -209,6 +208,8 @@ SYM_DATA_START_LOCAL(gdt)
> >  	.quad	0x00cf92000000ffff	/* __KERNEL_DS */
> >  SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end)
> >  
> > +SYM_DATA(boot_params, .long 0)
> > +
> 
> You should add a comment here that boot_params needs to be in the .data
> section because in .bss it would get zeroed out again later. Same
> applies to the 64bit version of this.
> 
> With that changed:
> 
> Reviewed-by: Joerg Roedel <jroedel@...e.de>
> 

Ok.