- Add a proper kernel cmdline option to control the TLB invalidation method on

x86 prompted mainly by a recent finding on AMD related to INVLPGB/TYLBSYNC
   invalidations. Having the command line option is simply another way to
   alleviate the situation short-term
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Merge tag 'x86_urgent_for_v7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fix from Borislav Petkov:

 - Add a proper kernel cmdline option to control the TLB invalidation
   method on x86 prompted mainly by a recent finding on AMD related to
   INVLPGB/TYLBSYNC invalidations.

   Having the command line option is simply another way to alleviate
   the situation short-term

* tag 'x86_urgent_for_v7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/CPU: Add a tlbi= cmdline switch

Documentation/admin-guide/kernel-parameters.txt

@@ -7568,6 +7568,10 @@ Kernel parameters
 			See Documentation/admin-guide/mm/transhuge.rst for more
 			details.
 
+	tlbi=		[X86-64]
+			Format: {ipi}
+			ipi: switch to IPI-based TLB flushing
+
 	topology=	[S390,EARLY]
 			Format: {off | on}
 			Specify if the kernel should make use of the cpu

arch/x86/kernel/cpu/common.c

@@ -2664,3 +2664,13 @@ void __init arch_cpu_finalize_init(void)
 	 */
 	mem_encrypt_init();
 }
+
+/* Control TLB flushing methods */
+static int __init tlbi_setup(char *str)
+{
+	if (!strcmp(str, "ipi"))
+		setup_clear_cpu_cap(X86_FEATURE_INVLPGB);
+
+	return 1;
+}
+__setup("tlbi=", tlbi_setup);