linux-kernel - Re: [patch 7/7 v2] x86: add xloadflags bit for efi runtime support on kexec

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Date:	Thu, 14 Nov 2013 09:36:49 +0800
From:	Dave Young <dyoung@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	x86@...nel.org, mjg59@...f.ucam.org,
	James.Bottomley@...senPartnership.com, vgoyal@...hat.com,
	ebiederm@...ssion.com, horms@...ge.net.au,
	kexec@...ts.infradead.org, bp@...en8.de
Subject: Re: [patch 7/7 v2] x86: add xloadflags bit for efi runtime support
 on kexec

On 11/13/13 at 08:20am, H. Peter Anvin wrote:
> On 11/05/2013 12:20 AM, dyoung@...hat.com wrote:
> > Old kexec-tools can not load new kernel. The reason is previously kexec-tools
> > do not fill efi_info in x86 setup header thus efi init fail and switch
> > to noefi boot. In new kexec-tools it will by default fill efi_info and
> > pass other efi required infomation to 2nd kernel so kexec kernel efi
> > initialization will success finally.
> > 
> > To prevent from breaking userspace, add a new xloadflags bit so kexec-tools
> > will check the flag and switch to old logic.
> > 
> > Signed-off-by: Dave Young <dyoung@...hat.com>
> > ---
> >  arch/x86/boot/header.S                |    9 ++++++++-
> >  arch/x86/include/uapi/asm/bootparam.h |    1 +
> >  2 files changed, 9 insertions(+), 1 deletion(-)
> > 
> > --- linux-2.6.orig/arch/x86/boot/header.S
> > +++ linux-2.6/arch/x86/boot/header.S
> > @@ -391,7 +391,14 @@ xloadflags:
> >  #else
> >  # define XLF23 0
> >  #endif
> > -			.word XLF0 | XLF1 | XLF23
> > +
> > +#if defined(CONFIG_X86_64) && defined(CONFIG_EFI)
> > +# define XLF4 XLF_EFI_KEXEC
> > +#else
> > +# define XLF4 0
> > +#endif
> > +
> > +			.word XLF0 | XLF1 | XLF23 | XLF4
> >  
> >  cmdline_size:   .long   COMMAND_LINE_SIZE-1     #length of the command line,
> >                                                  #added with boot protocol
> > --- linux-2.6.orig/arch/x86/include/uapi/asm/bootparam.h
> > +++ linux-2.6/arch/x86/include/uapi/asm/bootparam.h
> > @@ -24,6 +24,7 @@
> >  #define XLF_CAN_BE_LOADED_ABOVE_4G	(1<<1)
> >  #define XLF_EFI_HANDOVER_32		(1<<2)
> >  #define XLF_EFI_HANDOVER_64		(1<<3)
> > +#define XLF_EFI_KEXEC			(1<<4)
> >  
> >  #ifndef __ASSEMBLY__
> >  
> > 
> 
> Also needs to be added to Documentation/x86/boot.txt with the exact
> semantics being exposed.

Will do

> 
> 	-hpa
> 
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