[PATCH] x86, amd: modify the control_va_addr_alignment __setup handler

[Randy Dunlap]

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@xxxxxxxxxxxxx>
Reported-by: Igor Zhbanov <i.zhbanov@xxxxxxxxxxxx>
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@xxxxxxxxxxxx
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
---
 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,