diff mbox series

[for-stable-4.19] arm64: Use firmware to detect CPUs that are not affected by Spectre-v2

Message ID 20191009091023.19336-1-ard.biesheuvel@linaro.org
State Superseded
Headers show
Series [for-stable-4.19] arm64: Use firmware to detect CPUs that are not affected by Spectre-v2 | expand

Commit Message

Ard Biesheuvel Oct. 9, 2019, 9:10 a.m. UTC 
From: Marc Zyngier <marc.zyngier@arm.com>


[ Upstream commit 517953c2c47f9c00a002f588ac856a5bc70cede3 ]

The SMCCC ARCH_WORKAROUND_1 service can indicate that although the
firmware knows about the Spectre-v2 mitigation, this particular
CPU is not vulnerable, and it is thus not necessary to call
the firmware on this CPU.

Let's use this information to our benefit.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Tested-by: Stefan Wahren <stefan.wahren@i2se.com>

Signed-off-by: Will Deacon <will.deacon@arm.com>

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

---
 arch/arm64/kernel/cpu_errata.c | 32 ++++++++++++++------
 1 file changed, 23 insertions(+), 9 deletions(-)

-- 
2.20.1

Comments

Greg KH Oct. 9, 2019, 9:33 a.m. UTC | #1 
On Wed, Oct 09, 2019 at 11:10:23AM +0200, Ard Biesheuvel wrote:
> From: Marc Zyngier <marc.zyngier@arm.com>

> 

> [ Upstream commit 517953c2c47f9c00a002f588ac856a5bc70cede3 ]

> 

> The SMCCC ARCH_WORKAROUND_1 service can indicate that although the

> firmware knows about the Spectre-v2 mitigation, this particular

> CPU is not vulnerable, and it is thus not necessary to call

> the firmware on this CPU.

> 

> Let's use this information to our benefit.

> 

> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>

> Reviewed-by: Andre Przywara <andre.przywara@arm.com>

> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

> Tested-by: Stefan Wahren <stefan.wahren@i2se.com>

> Signed-off-by: Will Deacon <will.deacon@arm.com>

> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---

>  arch/arm64/kernel/cpu_errata.c | 32 ++++++++++++++------

>  1 file changed, 23 insertions(+), 9 deletions(-)


Now queued up, thanks.

greg k-h
diff mbox series

Patch

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index a9ad932160cc..c623b58a7e2b 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -198,22 +198,36 @@  static int detect_harden_bp_fw(void)
 	case PSCI_CONDUIT_HVC:
 		arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
 				  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
-		if ((int)res.a0 < 0)
+		switch ((int)res.a0) {
+		case 1:
+			/* Firmware says we're just fine */
+			return 0;
+		case 0:
+			cb = call_hvc_arch_workaround_1;
+			/* This is a guest, no need to patch KVM vectors */
+			smccc_start = NULL;
+			smccc_end = NULL;
+			break;
+		default:
 			return -1;
-		cb = call_hvc_arch_workaround_1;
-		/* This is a guest, no need to patch KVM vectors */
-		smccc_start = NULL;
-		smccc_end = NULL;
+		}
 		break;
 
 	case PSCI_CONDUIT_SMC:
 		arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
 				  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
-		if ((int)res.a0 < 0)
+		switch ((int)res.a0) {
+		case 1:
+			/* Firmware says we're just fine */
+			return 0;
+		case 0:
+			cb = call_smc_arch_workaround_1;
+			smccc_start = __smccc_workaround_1_smc_start;
+			smccc_end = __smccc_workaround_1_smc_end;
+			break;
+		default:
 			return -1;
-		cb = call_smc_arch_workaround_1;
-		smccc_start = __smccc_workaround_1_smc_start;
-		smccc_end = __smccc_workaround_1_smc_end;
+		}
 		break;
 
 	default: