From: tip-bot for Vlastimil Babka <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: tglx@linutronix.de, dave.hansen@intel.com, mingo@kernel.org,
ak@linux.intel.com, hpa@zytor.com, linux-kernel@vger.kernel.org,
mhocko@suse.com, vbabka@suse.cz, torvalds@linux-foundation.org
Subject: [tip:x86/urgent] x86/speculation/l1tf: Suggest what to do on systems with too much RAM
Date: Fri, 24 Aug 2018 00:55:32 -0700 [thread overview]
Message-ID: <tip-4b81eae3d37dee69231592182e1e34706f149a6e@git.kernel.org> (raw)
In-Reply-To: <966571f0-9d7f-43dc-92c6-a10eec7a1254@suse.cz>
Commit-ID: 4b81eae3d37dee69231592182e1e34706f149a6e
Gitweb: https://git.kernel.org/tip/4b81eae3d37dee69231592182e1e34706f149a6e
Author: Vlastimil Babka <vbabka@suse.cz>
AuthorDate: Thu, 23 Aug 2018 16:21:29 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 24 Aug 2018 09:51:14 +0200
x86/speculation/l1tf: Suggest what to do on systems with too much RAM
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
---
arch/x86/kernel/cpu/bugs.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index cb4a16292aa7..5c32b5006738 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -702,6 +702,10 @@ static void __init l1tf_select_mitigation(void)
half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT;
if (e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_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 Documentation/admin-guide/l1tf.rst might help you decide.\n");
return;
}
next prev parent reply other threads:[~2018-08-24 7:56 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-23 13:44 [PATCH] x86/speculation/l1tf: fix off-by-one error when warning that system has too much RAM Vlastimil Babka
2018-08-23 13:56 ` Michal Hocko
2018-08-23 14:28 ` [PATCH] x86/speculation/l1tf: suggest what to do on systems with " Vlastimil Babka
2018-08-23 15:46 ` Andi Kleen
2018-08-23 19:25 ` Michal Hocko
2018-08-23 19:38 ` Andi Kleen
2018-08-23 20:05 ` Michal Hocko
2018-08-23 22:07 ` Andi Kleen
2018-08-23 19:03 ` kbuild test robot
2018-08-23 19:23 ` kbuild test robot
2018-08-23 19:27 ` Michal Hocko
2018-08-24 7:32 ` Vlastimil Babka
2018-08-24 7:55 ` tip-bot for Vlastimil Babka [this message]
2018-08-24 10:36 ` Vlastimil Babka
2018-08-24 12:10 ` Vlastimil Babka
2018-08-24 12:20 ` Michal Hocko
2018-08-24 13:57 ` [tip:x86/urgent] x86/speculation/l1tf: Suggest " tip-bot for Vlastimil Babka
2018-08-23 15:44 ` [PATCH] x86/speculation/l1tf: fix off-by-one error when warning that system has " Andi Kleen
2018-08-23 20:20 ` Vlastimil Babka
2018-08-24 2:22 ` Andre Tomt
2018-08-24 3:35 ` Andi Kleen
2018-08-29 2:04 ` Christopher Snowhill
2018-08-24 8:52 ` xxxxxx xxxxxx
2018-08-24 7:55 ` [tip:x86/urgent] x86/speculation/l1tf: Fix " tip-bot for Vlastimil Babka
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