linux-kernel - Re: [PATCH 4.9 20/76] powerpc/64: Disable the speculation barrier from the command line

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Date:   Wed, 17 Apr 2019 18:41:20 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Diana Madalina Craciun <diana.craciun@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "stable\@vger.kernel.org" <stable@...r.kernel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.9 20/76] powerpc/64: Disable the speculation barrier from the command line

Diana Madalina Craciun <diana.craciun@....com> writes:
> Hi,
>
> I have tested the patches on NXP platforms and they worked as expected.

Thanks Diana.

cheers

> On 4/15/2019 9:45 PM, Greg Kroah-Hartman wrote:
>> commit cf175dc315f90185128fb061dc05b6fbb211aa2f upstream.
>>
>> The speculation barrier can be disabled from the command line
>> with the parameter: "nospectre_v1".
>>
>> Signed-off-by: Diana Craciun <diana.craciun@....com>
>> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  arch/powerpc/kernel/security.c | 12 +++++++++++-
>>  1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
>> index bf298d0c475f..813e38ff81ce 100644
>> --- a/arch/powerpc/kernel/security.c
>> +++ b/arch/powerpc/kernel/security.c
>> @@ -17,6 +17,7 @@
>>  unsigned long powerpc_security_features __read_mostly = SEC_FTR_DEFAULT;
>>
>>  bool barrier_nospec_enabled;
>> +static bool no_nospec;
>>
>>  static void enable_barrier_nospec(bool enable)
>>  {
>> @@ -43,9 +44,18 @@ void setup_barrier_nospec(void)
>>         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
>>                  security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
>>
>> -       enable_barrier_nospec(enable);
>> +       if (!no_nospec)
>> +               enable_barrier_nospec(enable);
>>  }
>>
>> +static int __init handle_nospectre_v1(char *p)
>> +{
>> +       no_nospec = true;
>> +
>> +       return 0;
>> +}
>> +early_param("nospectre_v1", handle_nospectre_v1);
>> +
>>  #ifdef CONFIG_DEBUG_FS
>>  static int barrier_nospec_set(void *data, u64 val)
>>  {
>> --
>> 2.19.1
>>
>>
>>
>>