From: Suzuki K Poulose suzuki.poulose@arm.com
[ Upstream commit 1d676673d665fd2162e7e466dcfbe5373bfdb73e ]
Currently we advertise the ID_AA6DFR0_EL1.TRACEVER for the guest, when the trace register accesses are trapped (CPTR_EL2.TTA == 1). So, the guest will get an undefined instruction, if trusts the ID registers and access one of the trace registers. Lets be nice to the guest and hide the feature to avoid unexpected behavior.
Even though this can be done at KVM sysreg emulation layer, we do this by removing the TRACEVER from the sanitised feature register field. This is fine as long as the ETM drivers can handle the individual trace units separately, even when there are differences among the CPUs.
Cc: Will Deacon will@kernel.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Mark Rutland mark.rutland@arm.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20210323120647.454211-2-suzuki.poulose@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kernel/cpufeature.c | 1 - 1 file changed, 1 deletion(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index b1f7bfadab9f..be6014fe5c3e 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -380,7 +380,6 @@ static const struct arm64_ftr_bits ftr_id_aa64dfr0[] = { * of support. */ S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_EXACT, ID_AA64DFR0_PMUVER_SHIFT, 4, 0), - ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64DFR0_TRACEVER_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64DFR0_DEBUGVER_SHIFT, 4, 0x6), ARM64_FTR_END, };