Re: [PATCH RFC 2/5] x86/speculation: Add support for 'cpu_spec_mitigations=' cmdline options

Randy Dunlap
2019-04-05T15:18:24Z

On 4/5/19 6:57 AM, Borislav Petkov wrote:
> On Thu, Apr 04, 2019 at 11:44:12AM -0500, Josh Poimboeuf wrote:
>> Configure x86 runtime CPU speculation bug mitigations in accordance with
>> the 'cpu_spec_mitigations=' cmdline options. This affects Meltdown,
>> Spectre v2, Speculative Store Bypass, and L1TF.
>>
>> The default behavior is unchanged.
>>
>> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
>> ---
>> .../admin-guide/kernel-parameters.txt | 15 +++++++++
>> arch/x86/include/asm/processor.h | 1 +
>> arch/x86/kernel/cpu/bugs.c | 32 ++++++++++++++++---
>> arch/x86/kvm/vmx/vmx.c | 2 ++
>> arch/x86/mm/pti.c | 4 ++-
>> 5 files changed, 49 insertions(+), 5 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index ac42e510bd6e..29dc03971630 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -2552,6 +2552,11 @@
>>
>> off
>> Disable all speculative CPU mitigations.
>> + Equivalent to: nopti [x86]
>> + nospectre_v2 [x86]
>> + spectre_v2_user=off [x86]
>> + spec_store_bypass_disable=off [x86]
>> + l1tf=off [x86]
>>
>> auto (default)
>> Mitigate all speculative CPU vulnerabilities,
>> @@ -2560,12 +2565,22 @@
>> surprised by SMT getting disabled across kernel
>> upgrades, or who have other ways of avoiding
>> SMT-based attacks.
>> + Equivalent to: pti=auto [x86]
>> + spectre_v2=auto [x86]
>> + spectre_v2_user=auto [x86]
>> + spec_store_bypass_disable=auto [x86]
>> + l1tf=flush [x86]
>>
>> auto,nosmt
>> Mitigate all speculative CPU vulnerabilities,
>> disabling SMT if needed. This is for users who
>> always want to be fully mitigated, even if it
>> means losing SMT.
>> + Equivalent to: pti=auto [x86]
>> + spectre_v2=auto [x86]
>> + spectre_v2_user=auto [x86]
>> + spec_store_bypass_disable=auto [x86]
>> + l1tf=flush,nosmt [x86]
>>
>> mminit_loglevel=
>> [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
>
> Yap, those sets look ok.

nit: s/x86/X86/g
according to Documentation/admin-guide/kernel-parameters.rst

--
~Randy