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arm64: errata: Add workaround for Arm errata 3194386 and 3312417

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Cortex-X4 and Neoverse-V3 suffer from errata whereby an MSR to the SSBS
special-purpose register does not affect subsequent speculative
instructions, permitting speculative store bypassing for a window of
time. This is described in their Software Developer Errata Notice (SDEN)
documents:

* Cortex-X4 SDEN v8.0, erratum 3194386:
  https://developer.arm.com/documentation/SDEN-2432808/0800/

* Neoverse-V3 SDEN v6.0, erratum 3312417:
  https://developer.arm.com/documentation/SDEN-2891958/0600/

To workaround these errata, it is necessary to place a speculation
barrier (SB) after MSR to the SSBS special-purpose register. This patch
adds the requisite SB after writes to SSBS within the kernel, and hides
the presence of SSBS from EL0 such that userspace software which cares
about SSBS will manipulate this via prctl(PR_GET_SPECULATION_CTRL, ...).

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20240508081400.235362-5-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Mark Rutland 2024-05-08 09:14:00 +01:00 committed by Will Deacon
parent 0ce85db6c2
commit 7187bb7d0b
7 changed files with 88 additions and 0 deletions
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4
Documentation/arch/arm64/silicon-errata.rst
View file

@ -140,6 +140,8 @@ stable kernels.
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-X2 | #2224489 | ARM64_ERRATUM_2224489 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Cortex-X4 | #3194386 | ARM64_ERRATUM_3194386 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-N1 | #1188873,1418040| ARM64_ERRATUM_1418040 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-N1 | #1349291 | N/A |
@ -156,6 +158,8 @@ stable kernels.
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-V1 | #1619801 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-V3 | #3312417 | ARM64_ERRATUM_3312417 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | MMU-500 | #841119,826419 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | MMU-600 | #1076982,1209401| N/A |

42
arch/arm64/Kconfig
View file

@ -1064,6 +1064,48 @@ config ARM64_ERRATUM_3117295
If unsure, say Y.
config ARM64_WORKAROUND_SPECULATIVE_SSBS
bool
config ARM64_ERRATUM_3194386
bool "Cortex-X4: 3194386: workaround for MSR SSBS not self-synchronizing"
select ARM64_WORKAROUND_SPECULATIVE_SSBS
default y
help
This option adds the workaround for ARM Cortex-X4 erratum 3194386.
On affected cores "MSR SSBS, #0" instructions may not affect
subsequent speculative instructions, which may permit unexepected
speculative store bypassing.
Work around this problem by placing a speculation barrier after
kernel changes to SSBS. The presence of the SSBS special-purpose
register is hidden from hwcaps and EL0 reads of ID_AA64PFR1_EL1, such
that userspace will use the PR_SPEC_STORE_BYPASS prctl to change
SSBS.
If unsure, say Y.
config ARM64_ERRATUM_3312417
bool "Neoverse-V3: 3312417: workaround for MSR SSBS not self-synchronizing"
select ARM64_WORKAROUND_SPECULATIVE_SSBS
default y
help
This option adds the workaround for ARM Neoverse-V3 erratum 3312417.
On affected cores "MSR SSBS, #0" instructions may not affect
subsequent speculative instructions, which may permit unexepected
speculative store bypassing.
Work around this problem by placing a speculation barrier after
kernel changes to SSBS. The presence of the SSBS special-purpose
register is hidden from hwcaps and EL0 reads of ID_AA64PFR1_EL1, such
that userspace will use the PR_SPEC_STORE_BYPASS prctl to change
SSBS.
If unsure, say Y.
config CAVIUM_ERRATUM_22375
bool "Cavium erratum 22375, 24313"
default y

2
arch/arm64/include/asm/cpucaps.h
View file

@ -58,6 +58,8 @@ cpucap_is_possible(const unsigned int cap)
return IS_ENABLED(CONFIG_NVIDIA_CARMEL_CNP_ERRATUM);
case ARM64_WORKAROUND_REPEAT_TLBI:
return IS_ENABLED(CONFIG_ARM64_WORKAROUND_REPEAT_TLBI);
case ARM64_WORKAROUND_SPECULATIVE_SSBS:
return IS_ENABLED(CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS);
}
return true;

19
arch/arm64/kernel/cpu_errata.c
View file

@ -432,6 +432,18 @@ static const struct midr_range erratum_spec_unpriv_load_list[] = {
};
#endif
#ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS
static const struct midr_range erratum_spec_ssbs_list[] = {
#ifdef CONFIG_ARM64_ERRATUM_3194386
MIDR_ALL_VERSIONS(MIDR_CORTEX_X4),
#endif
#ifdef CONFIG_ARM64_ERRATUM_3312417
MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V3),
#endif
{}
};
#endif
const struct arm64_cpu_capabilities arm64_errata[] = {
#ifdef CONFIG_ARM64_WORKAROUND_CLEAN_CACHE
{
@ -729,6 +741,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
MIDR_FIXED(MIDR_CPU_VAR_REV(1,1), BIT(25)),
},
#endif
#ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS
{
.desc = "ARM errata 3194386, 3312417",
.capability = ARM64_WORKAROUND_SPECULATIVE_SSBS,
ERRATA_MIDR_RANGE_LIST(erratum_spec_ssbs_list),
},
#endif
#ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_UNPRIV_LOAD
{
.desc = "ARM errata 2966298, 3117295",

8
arch/arm64/kernel/cpufeature.c
View file

@ -2307,6 +2307,14 @@ static void user_feature_fixup(void)
if (regp)
regp->user_mask &= ~ID_AA64ISAR1_EL1_BF16_MASK;
}
if (cpus_have_cap(ARM64_WORKAROUND_SPECULATIVE_SSBS)) {
struct arm64_ftr_reg *regp;
regp = get_arm64_ftr_reg(SYS_ID_AA64PFR1_EL1);
if (regp)
regp->user_mask &= ~ID_AA64PFR1_EL1_SSBS_MASK;
}
}
static void elf_hwcap_fixup(void)

12
arch/arm64/kernel/proton-pack.c
View file

@ -558,6 +558,18 @@ static enum mitigation_state spectre_v4_enable_hw_mitigation(void)
/* SCTLR_EL1.DSSBS was initialised to 0 during boot */
set_pstate_ssbs(0);
/*
* SSBS is self-synchronizing and is intended to affect subsequent
* speculative instructions, but some CPUs can speculate with a stale
* value of SSBS.
*
* Mitigate this with an unconditional speculation barrier, as CPUs
* could mis-speculate branches and bypass a conditional barrier.
*/
if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS))
spec_bar();
return SPECTRE_MITIGATED;
}

1
arch/arm64/tools/cpucaps
View file

@ -102,4 +102,5 @@ WORKAROUND_NVIDIA_CARMEL_CNP
WORKAROUND_QCOM_FALKOR_E1003
WORKAROUND_REPEAT_TLBI
WORKAROUND_SPECULATIVE_AT
WORKAROUND_SPECULATIVE_SSBS
WORKAROUND_SPECULATIVE_UNPRIV_LOAD