linux-kernel - Re: [PATCH v2 0/2] x86/kexec: Carry forward the boot DTB on kexec

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Message-ID: <aJ1MaPVWZCp0qpU2@MiWiFi-R3L-srv>
Date: Thu, 14 Aug 2025 10:39:36 +0800
From: Baoquan He <bhe@...hat.com>
To: Brian Mak <makb@...iper.net>
Cc: Dave Young <dyoung@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Graf <graf@...zon.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] x86/kexec: Carry forward the boot DTB on kexec

On 08/13/25 at 07:24pm, Brian Mak wrote:
> On Aug 12, 2025, at 8:54 PM, Dave Young <dyoung@...hat.com> wrote:
> 
> > Hi, The #ifdef CONFIG_* which can be replaced by #if defined(), but I
> > do not have a strong opinion.  other than that do you have kexec-tools
> > patch ready? It would be better to provide a link so that people can
> > try and test it.
> 
> Hi Dave,
> 
> Thanks for looking at this! The #ifdef CONFIG_* is used, as it matches
> the style of other ifdefs in this file. I'd like to keep it as-is for
> consistency.
> 
> I do have a prototype kexec-tools patch ready for testing. The changes
> can be found at this repo:
> 
> https://github.com/makb-juniper/kexec-tools.git
> 
> I've also placed the diff below.

Thanks, I will apply your patch and take a test.

Usually, Andrew will merge kexec/kdump patch if the patch is OK to him.
I will add comment if I have concern. Otherwise, I don't want Andrew to
bother to add my ACK.

> 
> diff --git a/kexec/kexec-syscall.h b/kexec/kexec-syscall.h
> index 9b17578..8419b23 100644
> --- a/kexec/kexec-syscall.h
> +++ b/kexec/kexec-syscall.h
> @@ -124,6 +124,8 @@ static inline long kexec_file_load(int kernel_fd, int initrd_fd,
>  #define KEXEC_FILE_ON_CRASH	0x00000002
>  #define KEXEC_FILE_NO_INITRAMFS	0x00000004
>  #define KEXEC_FILE_DEBUG	0x00000008
> +#define KEXEC_FILE_NO_CMA	0x00000010
> +#define KEXEC_FILE_FORCE_DTB	0x00000020
>  
>  /* These values match the ELF architecture values. 
>   * Unless there is a good reason that should continue to be the case.
> diff --git a/kexec/kexec.c b/kexec/kexec.c
> index 6bf12d7..0e13b6b 100644
> --- a/kexec/kexec.c
> +++ b/kexec/kexec.c
> @@ -1102,6 +1102,7 @@ void usage(void)
>  	       " --hotplug            Do in-kernel update of kexec segments on CPU/Memory\n"
>  	       "                      hot add/remove events, avoiding the need to reload\n"
>  	       "                      kdump kernel on online/offline events.\n"
> +	       " --force-dtb          Carry over the current boot's device tree blob (x86 only).\n"
>  	       " -d, --debug          Enable debugging to help spot a failure.\n"
>  	       " -S, --status         Return 1 if the type (by default crash) is loaded,\n"
>  	       "                      0 if not.\n"
> @@ -1640,6 +1641,9 @@ int main(int argc, char *argv[])
>  		case OPT_HOTPLUG:
>  			do_hotplug = 1;
>  			break;
> +		case OPT_FORCE_DTB:
> +			kexec_file_flags |= KEXEC_FILE_FORCE_DTB;
> +			break;
>  		default:
>  			break;
>  		}
> diff --git a/kexec/kexec.h b/kexec/kexec.h
> index a2e19c4..2235aa2 100644
> --- a/kexec/kexec.h
> +++ b/kexec/kexec.h
> @@ -235,7 +235,8 @@ extern int file_types;
>  #define OPT_LOAD_LIVE_UPDATE	263
>  #define OPT_EXEC_LIVE_UPDATE	264
>  #define OPT_HOTPLUG		        265
> -#define OPT_MAX		266
> +#define OPT_FORCE_DTB		266
> +#define OPT_MAX		267
>  #define KEXEC_OPTIONS \
>  	{ "help",		0, 0, OPT_HELP }, \
>  	{ "version",		0, 0, OPT_VERSION }, \
> @@ -263,6 +264,7 @@ extern int file_types;
>  	{ "status",		0, 0, OPT_STATUS }, \
>  	{ "print-ckr-size",     0, 0, OPT_PRINT_CKR_SIZE }, \
>  	{ "hotplug",		    0, 0, OPT_HOTPLUG }, \
> +	{ "force-dtb",          0, 0, OPT_FORCE_DTB }, \
>  
>  #define KEXEC_OPT_STR "h?vdfixyluet:pscaS"
>  
> 
> base-commit: daa29443819d3045338792b5ba950ed90e79d7a5
> -- 
> 2.25.1
>