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| author | Vlastimil Babka <vbabka@suse.cz> | 2018-06-21 12:36:29 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-15 17:37:27 +0200 |
| commit | f70abc9107e16ae881287889ad8980f74e902bb4 (patch) | |
| tree | fb05d0559a8860a5cee95fd80e1e378996be2fbb | |
| parent | 5b44df38ed667231be3cb7e161f184d987fd819d (diff) | |
| download | linux-f70abc9107e16ae881287889ad8980f74e902bb4.tar.gz | |
x86/speculation/l1tf: Extend 64bit swap file size limit
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/mm/init.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 1b530197d11490..c0870df32b2d36 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -891,7 +891,15 @@ 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; } |