linux-kernel - [v4.17-rcx] Lost IBPB, IBRS_FW support for spectre

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Date:   Mon, 30 Apr 2018 17:59:46 +0200
From:   Jörg Otte <jrg.otte@...il.com>
To:     kirill.shutemov@...ux.intel.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [v4.17-rcx] Lost IBPB, IBRS_FW support for spectre_v2 mitigation.

Hi,

In v4.16 I already had support for BPB, IBRS_FW for spectre_v2 mitigation.
But this went away in v17-rcx.

With 4.16 I have:
jojo@...hte:~$ cd /sys/devices/system/cpu/vulnerabilities; grep ".*" *
meltdown:Mitigation: PTI
spectre_v1:Mitigation: __user pointer sanitization
spectre_v2:Mitigation: Full generic retpoline, IBPB, IBRS_FW

With 4.17-rcx I have:
meltdown:Mitigation: PTI
spectre_v1:Mitigation: __user pointer sanitization
spectre_v2:Mitigation: Full generic retpoline

Processor is
vendor_id       : GenuineIntel
cpu family      : 6
model           : 60
model name      : Intel(R) Core(TM) i5-4200M CPU @ 2.50GHz
stepping        : 3
microcode       : 0x24


The problem goes away if I revert:
d94a155 x86/cpu: Prevent cpuinfo_x86::x86_phys_bits adjustment corruption

Thanks, Jörg