linux-kernel - Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support

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Date:   Wed, 28 Sep 2022 18:38:53 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Eric DeVolder <eric.devolder@...cle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, ebiederm@...ssion.com,
        dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        hpa@...or.com, nramas@...ux.microsoft.com, thomas.lendacky@....com,
        robh@...nel.org, efault@....de, rppt@...nel.org, david@...hat.com,
        sourabhjain@...ux.ibm.com, konrad.wilk@...cle.com,
        boris.ostrovsky@...cle.com
Subject: Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support

On Wed, Sep 28, 2022 at 06:07:24PM +0200, Borislav Petkov wrote:
>  #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
>  	/* Ensure elfcorehdr segment large enough for hotplug changes */
> @@ -407,9 +408,8 @@ int crash_load_segments(struct kimage *image)
>  	image->elf_headers_sz = kbuf.memsz;
>  	image->elfcorehdr_index = image->nr_segments;
>  	image->elfcorehdr_index_valid = true;

And that ifdeffery above can be made more readable too:

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index a526c893abe8..7aab6e942761 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -399,16 +399,15 @@ int crash_load_segments(struct kimage *image)
 	image->elf_headers_sz	= kbuf.bufsz;
 	kbuf.memsz		= kbuf.bufsz;
 
-#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
 	/* Ensure elfcorehdr segment large enough for hotplug changes */
-	kbuf.memsz =
-		(CONFIG_NR_CPUS_DEFAULT + CONFIG_CRASH_MAX_MEMORY_RANGES) *
-			sizeof(Elf64_Phdr);
-	/* Mark as usable to crash kernel, else crash kernel fails on boot */
-	image->elf_headers_sz = kbuf.memsz;
-	image->elfcorehdr_index = image->nr_segments;
-	image->elfcorehdr_index_valid = true;
-#endif
+	if (IS_ENABLED(CONFIG_CRASH_MAX_MEMORY_RANGES)) {
+		kbuf.memsz = (CONFIG_NR_CPUS_DEFAULT + CONFIG_CRASH_MAX_MEMORY_RANGES) * sizeof(Elf64_Phdr);
+
+		/* Mark as usable to crash kernel, else crash kernel fails on boot */
+		image->elf_headers_sz = kbuf.memsz;
+		image->elfcorehdr_index = image->nr_segments;
+		image->elfcorehdr_index_valid = true;
+	}
 
 	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
 	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;

-- 
Regards/Gruss,
    Boris.

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