From 9de4999050b5f2e847c84372c6a1aa1fe32bb269 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Thu, 2 Dec 2021 16:32:23 +0100 Subject: x86/realmode: Add comment for Global bit usage in trampoline_pgd Document the fact that using the trampoline_pgd will result in the creation of global TLB entries in the user range of the address space. Signed-off-by: Joerg Roedel Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20211202153226.22946-2-joro@8bytes.org --- arch/x86/mm/init.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'arch/x86/mm/init.c') diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 1895986842b9..4ba024d5b63a 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -714,6 +714,11 @@ static void __init memory_map_bottom_up(unsigned long map_start, static void __init init_trampoline(void) { #ifdef CONFIG_X86_64 + /* + * The code below will alias kernel page-tables in the user-range of the + * address space, including the Global bit. So global TLB entries will + * be created when using the trampoline page-table. + */ if (!kaslr_memory_enabled()) trampoline_pgd_entry = init_top_pgt[pgd_index(__PAGE_OFFSET)]; else -- cgit v1.2.3-70-g09d2