linux-kernel - Re: [PATCHv11 05/19] x86/relocate_kernel: Use named labels for less confusion

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Message-ID: <t3zx4f6ynru7qp4oel4syza2alcuxz7q7hxqgf2lxusgobnsnh@vtnecqrsxci5>
Date: Wed, 29 May 2024 14:17:29 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Nikolay Borisov <nik.borisov@...e.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, 
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>, Elena Reshetova <elena.reshetova@...el.com>, 
	Jun Nakajima <jun.nakajima@...el.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Tom Lendacky <thomas.lendacky@....com>, "Kalra, Ashish" <ashish.kalra@....com>, 
	Sean Christopherson <seanjc@...gle.com>, "Huang, Kai" <kai.huang@...el.com>, 
	Ard Biesheuvel <ardb@...nel.org>, Baoquan He <bhe@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, 
	"K. Y. Srinivasan" <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, 
	kexec@...ts.infradead.org, linux-hyperv@...r.kernel.org, linux-acpi@...r.kernel.org, 
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv11 05/19] x86/relocate_kernel: Use named labels for less
 confusion

On Wed, May 29, 2024 at 01:47:50PM +0300, Nikolay Borisov wrote:
> 
> 
> On 28.05.24 г. 12:55 ч., Kirill A. Shutemov wrote:
> > From: Borislav Petkov <bp@...en8.de>
> > 
> > That identity_mapped() functions was loving that "1" label to the point
> > of completely confusing its readers.
> > 
> > Use named labels in each place for clarity.
> > 
> > No functional changes.
> > 
> > Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > ---
> >   arch/x86/kernel/relocate_kernel_64.S | 13 +++++++------
> >   1 file changed, 7 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
> > index 56cab1bb25f5..085eef5c3904 100644
> > --- a/arch/x86/kernel/relocate_kernel_64.S
> > +++ b/arch/x86/kernel/relocate_kernel_64.S
> > @@ -148,9 +148,10 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
> >   	 */
> >   	movl	$X86_CR4_PAE, %eax
> >   	testq	$X86_CR4_LA57, %r13
> > -	jz	1f
> > +	jz	.Lno_la57
> >   	orl	$X86_CR4_LA57, %eax
> > -1:
> > +.Lno_la57:
> > +
> >   	movq	%rax, %cr4
> >   	jmp 1f
> 
> That jmp 1f becomes redundant now as it simply jumps 1 line below.
> 

Nothing changed wrt this jump. It dates back to initial kexec
implementation.

See 5234f5eb04ab ("[PATCH] kexec: x86_64 kexec implementation").

But I don't see functional need in it.

Anyway, it is outside of the scope of the patch.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov