[PATCH RFC 3/5] powerpc/speculation: Add support for 'cpu_spec_mitigations=' cmdline options

Josh Poimboeuf
2019-04-04T16:52:47Z

Configure powerpc CPU runtime speculation bug mitigations in accordance
with the 'cpu_spec_mitigations=' cmdline options. This affects
Meltdown, Spectre v1, Spectre v2, and Speculative Store Bypass.

The default behavior is unchanged.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
Documentation/admin-guide/kernel-parameters.txt | 9 +++++----
arch/powerpc/kernel/security.c | 6 +++---
arch/powerpc/kernel/setup_64.c | 2 +-
3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 29dc03971630..0e8eae1e8a25 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2552,10 +2552,11 @@

off
Disable all speculative CPU mitigations.
- Equivalent to: nopti [x86]
+ Equivalent to: nopti [x86, powerpc]
+ nospectre_v1 [powerpc]
nospectre_v2 [x86]
spectre_v2_user=off [x86]
- spec_store_bypass_disable=off [x86]
+ spec_store_bypass_disable=off [x86, powerpc]
l1tf=off [x86]

auto (default)
@@ -2568,7 +2569,7 @@
Equivalent to: pti=auto [x86]
spectre_v2=auto [x86]
spectre_v2_user=auto [x86]
- spec_store_bypass_disable=auto [x86]
+ spec_store_bypass_disable=auto [x86, powerpc]
l1tf=flush [x86]

auto,nosmt
@@ -2579,7 +2580,7 @@
Equivalent to: pti=auto [x86]
spectre_v2=auto [x86]
spectre_v2_user=auto [x86]
- spec_store_bypass_disable=auto [x86]
+ spec_store_bypass_disable=auto [x86, powerpc]
l1tf=flush,nosmt [x86]

mminit_loglevel=
diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index b33bafb8fcea..5aed4ad729ba 100644
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -57,7 +57,7 @@ void setup_barrier_nospec(void)
enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);

- if (!no_nospec)
+ if (!no_nospec && cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
enable_barrier_nospec(enable);
}

@@ -116,7 +116,7 @@ static int __init handle_nospectre_v2(char *p)
early_param("nospectre_v2", handle_nospectre_v2);
void setup_spectre_v2(void)
{
- if (no_spectrev2)
+ if (no_spectrev2 || cpu_spec_mitigations == CPU_SPEC_MITIGATIONS_OFF)
do_btb_flush_fixups();
else
btb_flush_enabled = true;
@@ -300,7 +300,7 @@ void setup_stf_barrier(void)

stf_enabled_flush_types = type;

- if (!no_stf_barrier)
+ if (!no_stf_barrier && cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
stf_barrier_enable(enable);
}

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index ba404dd9ce1d..d9d796a66a79 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -932,7 +932,7 @@ void setup_rfi_flush(enum l1d_flush_type types, bool enable)

enabled_flush_types = types;

- if (!no_rfi_flush)
+ if (!no_rfi_flush || cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
rfi_flush_enable(enable);
}

--
2.17.2