4.9-stable review patch. If anyone has any objections, please let me know.
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From: Vlastimil Babka vbabka@suse.cz
commit 1a7ed1ba4bba6c075d5ad61bb75e3fbc870840d6 upstream
The previous patch has limited swap file size so that large offsets cannot clear bits above MAX_PA/2 in the pte and interfere with L1TF mitigation.
It assumed that offsets are encoded starting with bit 12, same as pfn. But on x86_64, offsets are encoded starting with bit 9.
Thus the limit can be raised by 3 bits. That means 16TB with 42bit MAX_PA and 256TB with 46bit MAX_PA.
Fixes: 377eeaa8e11f ("x86/speculation/l1tf: Limit swap file size to MAX_PA/2") Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: David Woodhouse dwmw@amazon.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/mm/init.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
--- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -791,7 +791,15 @@ unsigned long max_swapfile_size(void)
if (boot_cpu_has_bug(X86_BUG_L1TF)) { /* Limit the swap file size to MAX_PA/2 for L1TF workaround */ - pages = min_t(unsigned long, l1tf_pfn_limit() + 1, pages); + unsigned long l1tf_limit = l1tf_pfn_limit() + 1; + /* + * We encode swap offsets also with 3 bits below those for pfn + * which makes the usable limit higher. + */ +#ifdef CONFIG_X86_64 + l1tf_limit <<= PAGE_SHIFT - SWP_OFFSET_FIRST_BIT; +#endif + pages = min_t(unsigned long, l1tf_limit, pages); } return pages; }