| From foo@baz Tue Aug 14 16:14:56 CEST 2018 |
| From: Vlastimil Babka <vbabka@suse.cz> |
| Date: Thu, 21 Jun 2018 12:36:29 +0200 |
| Subject: x86/speculation/l1tf: Extend 64bit swap file size limit |
| |
| 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; |
| } |
