linux-kernel - Re: [PATCH 03/29] x86/boot/e820: Simplify the PPro Erratum #50 workaround

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Message-ID: <aCW_0VyzQU10kwPx@gmail.com>
Date: Thu, 15 May 2025 12:20:01 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: linux-kernel@...r.kernel.org, Andy Shevchenko <andy@...nel.org>,
	Arnd Bergmann <arnd@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Juergen Gross <jgross@...e.com>, "H . Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mike Rapoport <rppt@...nel.org>,
	Paul Menzel <pmenzel@...gen.mpg.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH 03/29] x86/boot/e820: Simplify the PPro Erratum #50
 workaround


* Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> Mon, Apr 21, 2025 at 08:51:43PM +0200, Ingo Molnar kirjoitti:
> > No need to print out the table - users won't really be able
> > to tell much from it anyway and the messages around this
> > erratum are unnecessarily obtuse.
> > 
> > Instead clearly inform the user that a 256 kB hole is being
> > punched in their memory map at the 1.75 GB physical address.
> > 
> > Not that there are many PPro users left. :-)
> 
> ...
> 
> > +		e820__range_update(0x70000000ULL, 0x40000ULL, E820_TYPE_RAM, E820_TYPE_RESERVED);
> 
> Perhaps, 0x40000ULL --> SZ_256K ?

Indeed! I folded in the change below.

Thanks,

	Ingo

==============================>
 arch/x86/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index a1e2d64bb28d..f40dffc3e014 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -985,7 +985,7 @@ void __init setup_arch(char **cmdline_p)
 #ifdef CONFIG_X86_32
 	if (ppro_with_ram_bug()) {
 		pr_info("Applying PPro RAM bug workaround: punching 256 kB hole at 1.75 GB physical.\n");
-		e820__range_update(0x70000000ULL, 0x40000ULL, E820_TYPE_RAM, E820_TYPE_RESERVED);
+		e820__range_update(0x70000000ULL, SZ_256K, E820_TYPE_RAM, E820_TYPE_RESERVED);
 		e820__update_table(e820_table);
 	}
 #else