Re: [PATCH] x86/speculation/l1tf: suggest what to do on systems with too much RAM
From: Michal Hocko <mhocko@kernel.org>
Date: 2018-08-24 12:21:01
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On Fri 24-08-18 14:10:54, Vlastimil Babka wrote:
On 08/24/2018 12:36 PM, Vlastimil Babka wrote:quoted
On 08/24/2018 09:32 AM, Vlastimil Babka wrote:quoted
On 08/23/2018 09:27 PM, Michal Hocko wrote:quoted
On Thu 23-08-18 16:28:12, Vlastimil Babka wrote:quoted
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 <redacted>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.quoted
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<----quoted
From a650e6a4b989c6e029ac1ab4e0a68553e074ba7a Mon Sep 17 00:00:00 2001From: Vlastimil Babka <redacted> 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.
Yes, URL is much more convenient than a reference to the kernel source documentation. If the link below is meant to be long lived then sure.
Signed-off-by: Vlastimil Babka <redacted>
Acked-by: Michal Hocko <mhocko@suse.com>
quoted hunk ↗ jump to hunk
--- 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; }-- 2.18.0
-- Michal Hocko SUSE Labs