[Bug 1085958] New: when nospectre_v2 be used spec_ctrl flags only disappear on Core0

bugzilla_noreply＠novell.com

20 Mar 2018 20 Mar '18

06:05

http://bugzilla.suse.com/show_bug.cgi?id=1085958 Bug ID: 1085958 Summary: when nospectre_v2 be used spec_ctrl flags only disappear on Core0 Classification: openSUSE Product: openSUSE Distribution Version: Leap 42.3 Hardware: Other OS: Other Status: NEW Severity: Normal Priority: P5 - None Component: Kernel Assignee: kernel-maintainers@forge.provo.novell.com Reporter: jnwang@suse.com QA Contact: qa-bugs@suse.de Found By: --- Blocker: --- When I use nospectre_v2 on kernel cmdline, lscpu doesn't display spec_ctrl flags. but when I cat /proc/cpuinfo | grep spec_ctrl: I will see spec_ctrl flag on other logic core except core0. kernel version: 4.4.120-8.g7186d16-default http://download.opensuse.org/repositories/Kernel:/openSUSE-42.3/standard/ -- You are receiving this mail because: You are on the CC list for the bug.

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bugzilla_noreply＠novell.com

20 Mar 20 Mar

06:12

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 James Wang changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bpetkov@suse.com, | |jkosina@suse.com -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

27 Mar 27 Mar

16:04

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 Takashi Iwai changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jslaby@suse.com, | |tiwai@suse.com -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

29 Mar 29 Mar

09:28

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 http://bugzilla.suse.com/show_bug.cgi?id=1085958#c1 Jiri Slaby changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |CONFIRMED --- Comment #1 from Jiri Slaby --- Ugh, oh my. The interaction of upstream vs. non-upstream spectre v2 handling is in start_kernel as follows:

...

parse_early_param nospec <- if passed "nospec" parameter check_bugs identify_boot_cpu identify_cpu(boot_cpu_data) init_intel x86_spec_check -> non-upstream IBRS setup_force_cpu_cap(X86_FEATURE_SPEC_CTRL) apply_forced_caps spectre_v2_select_mitigation spectre_v2_parse_cmdline nospec -> set by "nospectre_v2" param setup_clear_cpu_cap(X86_FEATURE_SPEC_CTRL) rest_init kernel_init kernel_init_freeable smp_init -> distribute

So non-upstream spec v2 sets the forced flag, but later call to nospec won't help, as it does not remove forced flag to be cleared. So nospectre_v2 removes the flag only from the boot cpu. This should fix it: --- a/arch/x86/kernel/cpu/spec_ctrl.c +++ b/arch/x86/kernel/cpu/spec_ctrl.c @@ -100,3 +100,4 @@ int nospec(char *str) return 0; } early_param("nospec", nospec); +early_param("nospectre_v2", nospec); -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

09:37

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 http://bugzilla.suse.com/show_bug.cgi?id=1085958#c2 --- Comment #2 from Jiri Slaby --- Building at: https://build.opensuse.org/project/monitor?project=home%3Ajirislaby%3Abnc108... Check it once it's built. -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

09:56

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 http://bugzilla.suse.com/show_bug.cgi?id=1085958#c3 Borislav Petkov changed: What |Removed |Added ---------------------------------------------------------------------------- Flags| |needinfo?(jkosina@suse.com) --- Comment #3 from Borislav Petkov --- Actually, the logic we came up with there is to set ibrs_state and ibpb_state to 0 if nospec has disabled them. Otherwise they're initalized to -1 to differentiate that no cmdline switch was supplied. And x86_spec_check() should look at ibrs_state too at entry, I wonder why jikos is looking at ibpb_state only. jikos? -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

9 Apr 9 Apr

08:32

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 Borislav Petkov changed: What |Removed |Added ---------------------------------------------------------------------------- Flags|needinfo?(jkosina@suse.com) | -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

08:46

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 http://bugzilla.suse.com/show_bug.cgi?id=1085958#c6 Jiri Slaby changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jnwang@suse.com Flags| |needinfo?(jnwang@suse.com) --- Comment #6 from Jiri Slaby --- (In reply to Jiri Slaby from comment #2)

...

Check it once it's built.

Ping -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

09:17

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 http://bugzilla.suse.com/show_bug.cgi?id=1085958#c7 --- Comment #7 from James Wang --- Created attachment 766406 --> http://bugzilla.suse.com/attachment.cgi?id=766406&action=edit verify Jslaby's kernel with nospectre_v2 -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

09:21

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 http://bugzilla.suse.com/show_bug.cgi?id=1085958#c8 --- Comment #8 from James Wang --- Created attachment 766408 --> http://bugzilla.suse.com/attachment.cgi?id=766408&action=edit verify Jslaby's kernel without nospectre_v2 -- You are receiving this mail because: You are on the CC list for the bug.

bugzilla_noreply＠novell.com

09:22

New subject: [Bug 1085958] when nospectre_v2 be used spec_ctrl flags only disappear on Core0

http://bugzilla.suse.com/show_bug.cgi?id=1085958 http://bugzilla.suse.com/show_bug.cgi?id=1085958#c9 James Wang changed: What |Removed |Added ---------------------------------------------------------------------------- Flags|needinfo?(jnwang@suse.com) | --- Comment #9 from James Wang --- Verify fix on (In reply to Jiri Slaby from comment #2)

...

Building at:

https://build.opensuse.org/project/ monitor?project=home%3Ajirislaby%3Abnc1085958

Check it once it's built.

It works. -- You are receiving this mail because: You are on the CC list for the bug.