There are a few places where the idreg overrides are read w/ the MMU off, for example the VHE and hVHE checks in __finalise_el2. And while the infrastructure gets this _mostly_ right (i.e. does the appropriate cache maintenance), the placement of the data itself is problematic and could share a cache line with something else.
Depending on how unforgiving an implementation's handling of mismatched attributes is, this could lead to data corruption. In one observed case, the system_cpucaps shared a line with arm64_sw_feature_override and the cpucaps got nuked after entering the hyp stub...
Even though only a few overrides are read without the MMU on, just throw the whole lot into the mmuoff section and be done with it.
Cc: stable@vger.kernel.org # v5.15+ Tested-by: Moritz Fischer moritzf@google.com Tested-by: Pedro Martelletto martelletto@google.com Reported-by: Jon Masters jonmasters@google.com Signed-off-by: Oliver Upton oliver.upton@linux.dev --- arch/arm64/kernel/cpufeature.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index d41128e37701..92506d9f90db 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -755,17 +755,20 @@ static const struct arm64_ftr_bits ftr_raz[] = { #define ARM64_FTR_REG(id, table) \ __ARM64_FTR_REG_OVERRIDE(#id, id, table, &no_override)
-struct arm64_ftr_override id_aa64mmfr0_override; -struct arm64_ftr_override id_aa64mmfr1_override; -struct arm64_ftr_override id_aa64mmfr2_override; -struct arm64_ftr_override id_aa64pfr0_override; -struct arm64_ftr_override id_aa64pfr1_override; -struct arm64_ftr_override id_aa64zfr0_override; -struct arm64_ftr_override id_aa64smfr0_override; -struct arm64_ftr_override id_aa64isar1_override; -struct arm64_ftr_override id_aa64isar2_override; - -struct arm64_ftr_override arm64_sw_feature_override; +#define DEFINE_FTR_OVERRIDE(name) \ + struct arm64_ftr_override __section(".mmuoff.data.read") name + +DEFINE_FTR_OVERRIDE(id_aa64mmfr0_override); +DEFINE_FTR_OVERRIDE(id_aa64mmfr1_override); +DEFINE_FTR_OVERRIDE(id_aa64mmfr2_override); +DEFINE_FTR_OVERRIDE(id_aa64pfr0_override); +DEFINE_FTR_OVERRIDE(id_aa64pfr1_override); +DEFINE_FTR_OVERRIDE(id_aa64zfr0_override); +DEFINE_FTR_OVERRIDE(id_aa64smfr0_override); +DEFINE_FTR_OVERRIDE(id_aa64isar1_override); +DEFINE_FTR_OVERRIDE(id_aa64isar2_override); + +DEFINE_FTR_OVERRIDE(arm64_sw_feature_override);
static const struct __ftr_reg_entry { u32 sys_id;
base-commit: 1dd3393696efba1598aa7692939bba99d0cffae3