On 08/24/2018 12:36 PM, Vlastimil Babka wrote:
On 08/24/2018 09:32 AM, Vlastimil Babka wrote:
On 08/23/2018 09:27 PM, Michal Hocko wrote:
On Thu 23-08-18 16:28:12, Vlastimil Babka wrote:
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. Let's make the warning more helpful by suggesting the proper mem=X kernel boot param, a rough calculation of how much RAM can be lost (not precise if there's holes between MAX_PA/2 and max_pfn in the e820 map) 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 Cc: stable@vger.kernel.org Signed-off-by: Vlastimil Babka vbabka@suse.cz
I wouldn't bother with max_pfn-half_pa part but other than that this is much more useful than the original message.
Right, and it causes build failures on some configs.
Acked-by: Michal Hocko mhocko@suse.com
Thanks! Here's a v2:
Just realized that kvm printk's refer to the online version at https://www.kernel.org/doc/html/latest/admin-guide/l1tf.html which should be easier for the users of distro kernels, should I change that?
FWIW, if it's not possible to amend anymore... ----8<----
From a650e6a4b989c6e029ac1ab4e0a68553e074ba7a Mon Sep 17 00:00:00 2001
From: Vlastimil Babka vbabka@suse.cz Date: Fri, 24 Aug 2018 14:05:45 +0200 Subject: [PATCH] x86/speculation/l1tf: replace Documentation path with kernel.org URL
The URL might be easier to reach for users of distro kernels without unpacked source, and be more up-to-date. It's also used in KVM warnings related to L1TF.
Signed-off-by: Vlastimil Babka vbabka@suse.cz --- arch/x86/kernel/cpu/bugs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 5c32b5006738..4c2313d0b9ca 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -705,7 +705,7 @@ static void __init l1tf_select_mitigation(void) 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 Documentation/admin-guide/l1tf.rst might help you decide.\n"); + pr_info("Reading https://www.kernel.org/doc/html/latest/admin-guide/l1tf.html might help you decide.\n"); return; }