From: Rik van Riel Date: Thu, 6 Aug 2026 15:54:57 +0000 (-0700) Subject: x86/CPU: Add a tlbi= cmdline switch X-Git-Tag: v7.2~7^2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=abe7c8b09bd72a9c726016257c6281f129b4c02d;p=thirdparty%2Fkernel%2Flinux.git x86/CPU: Add a tlbi= cmdline switch With the recently found INVLPGB / TLBSYNC issue, there has been some interest in disabling INVLPGB-based TLB flushing, in order to rule out that CPU issue as a cause of userspace crashes. Add a kernel command line option to control the TLB flushing behavior. If the need arises, we will add a "tlbi=broadcast" for the case when TLB invalidation broadcasts need to be explicitly selected, but this is not needed now yet. [ bp: Rewrite commit message, move to cpu/common.c, add documentation. ] Fixes: 767ae437a32d ("x86/mm: Add INVLPGB feature and Kconfig entry") Suggested-by: Borislav Petkov Signed-off-by: Rik van Riel Signed-off-by: Borislav Petkov (AMD) Cc: Link: https://patch.msgid.link/20260729204341.3eb0b5ea@fangorn --- diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3d35270dddef..e8ff36982d97 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/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 diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index a3df21d26460..a3caddd411ec 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/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);