linux-kernel - [PATCH] x86, amd: modify the control_va_addr_alignment _

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Message-Id: <20220315001045.7680-1-rdunlap@infradead.org>
Date:   Mon, 14 Mar 2022 17:10:45 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     linux-kernel@...r.kernel.org
Cc:     patches@...ts.linux.dev, Randy Dunlap <rdunlap@...radead.org>,
        Igor Zhbanov <i.zhbanov@...russia.ru>,
        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>, x86@...nel.org
Subject: [PATCH] x86, amd: modify the control_va_addr_alignment __setup handler

Clean up control_va_addr_alignment():

a. Make '=' required instead of optional (as documented).
b. Print a warning if an invalid option value is used.
c. Return 1 from the __setup handler when an invalid option value is
   used. This prevents the kernel from polluting init's (limited)
   environment space with the entire string.

Fixes: dfb09f9b7ab0 ("x86, amd: Avoid cache aliasing penalties on AMD family 15h")
Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
Reported-by: Igor Zhbanov <i.zhbanov@...russia.ru>
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@...russia.ru
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
---
 arch/x86/kernel/sys_x86_64.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- lnx-517-rc8.orig/arch/x86/kernel/sys_x86_64.c
+++ lnx-517-rc8/arch/x86/kernel/sys_x86_64.c
@@ -68,9 +68,6 @@ static int __init control_va_addr_alignm
 	if (*str == 0)
 		return 1;
 
-	if (*str == '=')
-		str++;
-
 	if (!strcmp(str, "32"))
 		va_align.flags = ALIGN_VA_32;
 	else if (!strcmp(str, "64"))
@@ -80,11 +77,11 @@ static int __init control_va_addr_alignm
 	else if (!strcmp(str, "on"))
 		va_align.flags = ALIGN_VA_32 | ALIGN_VA_64;
 	else
-		return 0;
+		pr_warn("invalid option value: 'align_va_addr=%s'\n", str);
 
 	return 1;
 }
-__setup("align_va_addr", control_va_addr_alignment);
+__setup("align_va_addr=", control_va_addr_alignment);
 
 SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
 		unsigned long, prot, unsigned long, flags,