linux-kernel - [PATCH v2 3/6] arm64: errata: Add QCOM_KRYO_4XX_GOLD to the spectre_bhb_k24

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Message-ID: <20241213165201.v2.3.Ie4ef54abe02e7eb0eee50f830575719bf23bda48@changeid>
Date: Fri, 13 Dec 2024 16:52:04 -0800
From: Douglas Anderson <dianders@...omium.org>
To: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>
Cc: linux-arm-msm@...r.kernel.org,
	Jeffrey Hugo <quic_jhugo@...cinc.com>,
	Julius Werner <jwerner@...omium.org>,
	linux-arm-kernel@...ts.infradead.org,
	Roxana Bradescu <roxabee@...gle.com>,
	Trilok Soni <quic_tsoni@...cinc.com>,
	bjorn.andersson@....qualcomm.com,
	Douglas Anderson <dianders@...omium.org>,
	stable@...r.kernel.org,
	James Morse <james.morse@....com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/6] arm64: errata: Add QCOM_KRYO_4XX_GOLD to the spectre_bhb_k24_list

Qualcomm Kryo 400-series Gold cores appear to have a derivative of an
ARM Cortex A76 in them. Since A76 needs Spectre mitigation via looping
then the Kyro 400-series Gold cores also should need Spectre
mitigation via looping.

Fixes: 558c303c9734 ("arm64: Mitigate spectre style branch history side channels")
Cc: stable@...r.kernel.org
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---
The "k" value here really should come from analysis by Qualcomm, but
until we can get that analysis let's choose the same value as A76: 24.

Ideally someone from Qualcomm can confirm that this mitigation is
needed and confirm / provide the proper "k" value.

...or do people think that this should go in the k32 list to be
safe. At least adding it to the list of CPUs we don't warn about seems
like a good idea since it seems very unlikely that it needs a FW
mitigation when the A76 it's based on doesn't.

...or should we just drop this until Qualcomm tells us the right "k"
value here?

Changes in v2:
- Slight change to wording and notes of KRYO_4XX_GOLD patch

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

diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
index 012485b75019..04c3f0567999 100644
--- a/arch/arm64/kernel/proton-pack.c
+++ b/arch/arm64/kernel/proton-pack.c
@@ -887,6 +887,7 @@ u8 spectre_bhb_loop_affected(int scope)
 			MIDR_ALL_VERSIONS(MIDR_CORTEX_A76),
 			MIDR_ALL_VERSIONS(MIDR_CORTEX_A77),
 			MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
+			MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_GOLD),
 			{},
 		};
 		static const struct midr_range spectre_bhb_k11_list[] = {
-- 
2.47.1.613.gc27f4b7a9f-goog