diff options
| author | Vlastimil Babka <vbabka@suse.cz> | 2018-08-23 16:21:29 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-09-05 09:18:38 +0200 |
| commit | 72f6531162bd2f1b57e8114c8358fca507090f41 (patch) | |
| tree | a01adcad9d1db596c2dcf5bd94050c1744e1b900 | |
| parent | 7b69cd6fa088e473869512672969e6c490cac1b6 (diff) | |
x86/speculation/l1tf: Suggest what to do on systems with too much RAM
commit 6a012288d6906fee1dbc244050ade1dafe4a9c8d upstream.
Two users have reported [1] that they have an "extremely unlikely" system
with more than MAX_PA/2 memory and L1TF mitigation is not effective.
Make the warning more helpful by suggesting the proper mem=X kernel boot
parameter to make it effective and a link to the L1TF document to help
decide if the mitigation is worth the unusable RAM.
[1] https://bugzilla.suse.com/show_bug.cgi?id=1105536
Suggested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/966571f0-9d7f-43dc-92c6-a10eec7a1254@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 34e4aaaf03d2..b9e6b60df148 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -654,6 +654,10 @@ static void __init l1tf_select_mitigation(void) half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT; if (e820_any_mapped(half_pa, ULLONG_MAX - half_pa, E820_RAM)) { pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n"); + pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n", + half_pa); + pr_info("However, doing so will make a part of your RAM unusable.\n"); + pr_info("Reading https://www.kernel.org/doc/html/latest/admin-guide/l1tf.html might help you decide.\n"); return; } |