From: Vlastimil Babka <vbabka@suse.cz> To: Michal Hocko <mhocko@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>, x86@kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@linux-foundation.org>, Andi Kleen <ak@linux.intel.com>, Dave Hansen <dave.hansen@intel.com>, stable@vger.kernel.org Subject: Re: [PATCH] x86/speculation/l1tf: suggest what to do on systems with too much RAM Date: Fri, 24 Aug 2018 09:32:00 +0200 [thread overview] Message-ID: <966571f0-9d7f-43dc-92c6-a10eec7a1254@suse.cz> (raw) In-Reply-To: <20180823192709.GT29735@dhcp22.suse.cz> 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: ----8<---- From 977c5db27fe35a84807850b947bc5678c4d467b3 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka <vbabka@suse.cz> Date: Thu, 23 Aug 2018 16:21:29 +0200 Subject: [PATCH] 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. Let's make the warning more helpful by suggesting the proper mem=X kernel boot param 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> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Vlastimil Babka <vbabka@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; } -- 2.18.0
WARNING: multiple messages have this Message-ID (diff)
From: Vlastimil Babka <vbabka@suse.cz> To: Michal Hocko <mhocko@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>, x86@kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@linux-foundation.org>, Andi Kleen <ak@linux.intel.com>, Dave Hansen <dave.hansen@intel.com>, stable@vger.kernel.org Subject: Re: [PATCH] x86/speculation/l1tf: suggest what to do on systems with too much RAM Date: Fri, 24 Aug 2018 09:32:00 +0200 [thread overview] Message-ID: <966571f0-9d7f-43dc-92c6-a10eec7a1254@suse.cz> (raw) In-Reply-To: <20180823192709.GT29735@dhcp22.suse.cz> 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: ----8<---- >From 977c5db27fe35a84807850b947bc5678c4d467b3 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka <vbabka@suse.cz> Date: Thu, 23 Aug 2018 16:21:29 +0200 Subject: [PATCH] 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. Let's make the warning more helpful by suggesting the proper mem=X kernel boot param 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> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Vlastimil Babka <vbabka@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; } -- 2.18.0
next prev parent reply other threads:[~2018-08-24 7:32 UTC|newest] Thread overview: 26+ 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 [this message] 2018-08-24 7:32 ` Vlastimil Babka 2018-08-24 7:55 ` [tip:x86/urgent] x86/speculation/l1tf: Suggest " tip-bot for Vlastimil Babka 2018-08-24 10:36 ` [PATCH] x86/speculation/l1tf: suggest " Vlastimil Babka 2018-08-24 12:10 ` 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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