lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 16 Dec 2020 13:38:05 +0100
From:   Jessica Yu <>
To:     Peter Zijlstra <>
Cc:     Dexuan Cui <>, Ingo Molnar <>,
        Daniel Bristot de Oliveira <>,
        "" <>,
        "" <>,
        Josh Poimboeuf <>
Subject: Re: static_branch_enable() does not work from a __init function?

+++ Peter Zijlstra [16/12/20 10:26 +0100]:
>On Wed, Dec 16, 2020 at 03:54:29AM +0000, Dexuan Cui wrote:
>> PS, I originally found: in arch/x86/kvm/vmx/vmx.c: vmx_init(), it looks
>> like the line "static_branch_enable(&enable_evmcs);" does not take effect
>> in a v5.4-based kernel, but does take effect in the v5.10 kernel in the
>> same x86-64 virtual machine on Hyper-V, so I made the above test module
>> to test static_branch_enable(), and found that static_branch_enable() in
>> the test module does not work with both v5.10 and my v5.4 kernel, if the
>> __init marker is used.

By the way, it probably works now because there was a workaround
merged in v5.10, that mentions this very issue:

commit 064eedf2c50f692088e1418c553084bf9c1432f8
Author: Vitaly Kuznetsov <>
Date:   Wed Oct 14 16:33:46 2020 +0200

    KVM: VMX: eVMCS: make evmcs_sanitize_exec_ctrls() work again

    It was noticed that evmcs_sanitize_exec_ctrls() is not being executed
    nowadays despite the code checking 'enable_evmcs' static key looking
    correct. Turns out, static key magic doesn't work in '__init' section
    (and it is unclear when things changed) but setup_vmcs_config() is called
    only once per CPU so we don't really need it to. Switch to checking
    'enlightened_vmcs' instead, it is supposed to be in sync with

    Opportunistically make evmcs_sanitize_exec_ctrls '__init' and drop unneeded
    extra newline from it.

    Reported-by: Yang Weijiang <>
    Signed-off-by: Vitaly Kuznetsov <>
    Message-Id: <>
    Signed-off-by: Paolo Bonzini <>

Powered by blists - more mailing lists