Commit 10a70416 authored Jun 13, 2018 by Andi Kleen Committed by Thomas Gleixner Jun 20, 2018

x86/speculation/l1tf: Make sure the first page is always reserved



The L1TF workaround doesn't make any attempt to mitigate speculate accesses
to the first physical page for zeroed PTEs. Normally it only contains some
data from the early real mode BIOS.

It's not entirely clear that the first page is reserved in all
configurations, so add an extra reservation call to make sure it is really
reserved. In most configurations (e.g.  with the standard reservations)
it's likely a nop.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>

parent 6b28baca

arch/x86/kernel/setup.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -823,6 +823,12 @@ void __init setup_arch(char **cmdline_p)
		memblock_reserve(__pa_symbol(_text),
		(unsigned long)__bss_stop - (unsigned long)_text);

		/*
		* Make sure page 0 is always reserved because on systems with
		* L1TF its contents can be leaked to user processes.
		*/
		memblock_reserve(0, PAGE_SIZE);

		early_reserve_initrd();

		/*

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