[v2,6/6] arm64: errata: Add QCOM_KRYO_3XX_GOLD to the spectre_bhb_firmware_mitigated_list

Commit Message

Douglas Anderson Dec. 14, 2024, 12:52 a.m. UTC

Qualcomm Kryo 200-series Gold cores appear to have a derivative of an
ARM Cortex A75 in them. Since A75 needs Spectre mitigation via
firmware then the Kyro 300-series Gold cores also should need Spectre
mitigation via firmware.

Unless devices with a Kryo 3XX gold core have a firmware that provides
ARM_SMCCC_ARCH_WORKAROUND_3 (which seems unlikely at the time this
patch is posted), this will make devices with these cores report that
they are vulnerable to Spectre BHB with no mitigation in place. This
patch will also cause them not to do a WARN splat at boot about an
unknown CPU ID and to stop trying to do a "loop" mitigation for these
cores which is (presumably) not reliable for them.

Fixes: 558c303c9734 ("arm64: Mitigate spectre style branch history side channels")
Cc: [e-mail]
Signed-off-by: Douglas Anderson <[e-mail]>
---
I don't really have any good way to test this patch but it seems
likely it's needed.

NOTE: presumably this patch won't actually do much on its own because
(I believe) it requires a firmware update (one adding
ARM_SMCCC_ARCH_WORKAROUND_3) to go with it.

Changes in v2:
- Rebased / reworded QCOM_KRYO_3XX_GOLD patch

 arch/arm64/kernel/proton-pack.c | 1 +
 1 file changed, 1 insertion(+)

Patch

diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
index 3b179a1bf815..f8e0d87d9e2d 100644
--- a/arch/arm64/kernel/proton-pack.c
+++ b/arch/arm64/kernel/proton-pack.c
@@ -845,6 +845,7 @@  static const struct midr_range spectre_bhb_firmware_mitigated_list[] = {
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A75),
 	MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_2XX_GOLD),
+	MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_3XX_GOLD),
 	{},
 };