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From: Jeremy Linton <jeremy.linton@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: stefan.wahren@i2se.com, mlangsdo@redhat.com,
	suzuki.poulose@arm.com, marc.zyngier@arm.com,
	catalin.marinas@arm.com, julien.thierry@arm.com,
	will.deacon@arm.com, linux-kernel@vger.kernel.org,
	Jeremy Linton <jeremy.linton@arm.com>,
	steven.price@arm.com, ykaukab@suse.de, dave.martin@arm.com,
	shankerd@codeaurora.org
Subject: [PATCH v4 09/12] arm64: Use firmware to detect CPUs that are not affected by Spectre-v2
Date: Fri, 25 Jan 2019 12:07:08 -0600	[thread overview]
Message-ID: <20190125180711.1970973-10-jeremy.linton@arm.com> (raw)
In-Reply-To: <20190125180711.1970973-1-jeremy.linton@arm.com>

From: Marc Zyngier <marc.zyngier@arm.com>

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

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 4d23b4d4cfa8..024c83ffff99 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -217,22 +217,36 @@ 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:
-- 
2.17.2


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  parent reply	other threads:[~2019-01-25 18:09 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-25 18:06 [PATCH v4 00/12] arm64: add system vulnerability sysfs entries Jeremy Linton
2019-01-25 18:07 ` [PATCH v4 01/12] Documentation: Document arm64 kpti control Jeremy Linton
2019-01-30 18:02   ` Andre Przywara
2019-02-06 19:24     ` Jeremy Linton
2019-02-06 21:06       ` André Przywara
2019-01-31 17:58   ` Andre Przywara
2019-02-07  0:25   ` Jonathan Corbet
2019-01-25 18:07 ` [PATCH v4 02/12] arm64: Provide a command line to disable spectre_v2 mitigation Jeremy Linton
2019-01-30 18:03   ` Andre Przywara
2019-01-25 18:07 ` [PATCH v4 03/12] arm64: Remove the ability to build a kernel without ssbd Jeremy Linton
2019-01-30 18:04   ` Andre Przywara
2019-02-15 18:20     ` Catalin Marinas
2019-02-15 18:54       ` Jeremy Linton
2019-01-25 18:07 ` [PATCH v4 04/12] arm64: remove the ability to build a kernel without hardened branch predictors Jeremy Linton
2019-01-30 18:04   ` Andre Przywara
2019-01-25 18:07 ` [PATCH v4 05/12] arm64: remove the ability to build a kernel without kpti Jeremy Linton
2019-01-30 18:05   ` Andre Przywara
2019-01-25 18:07 ` [PATCH v4 06/12] arm64: add sysfs vulnerability show for spectre v1 Jeremy Linton
2019-01-31 17:52   ` Andre Przywara
2019-01-25 18:07 ` [PATCH v4 07/12] arm64: add sysfs vulnerability show for meltdown Jeremy Linton
2019-01-31  9:28   ` Julien Thierry
2019-01-31 21:48     ` Jeremy Linton
2019-01-31 17:54   ` Andre Przywara
2019-01-31 21:53     ` Jeremy Linton
2019-01-25 18:07 ` [PATCH v4 08/12] arm64: Advertise mitigation of Spectre-v2, or lack thereof Jeremy Linton
2019-01-31 17:54   ` Andre Przywara
2019-01-25 18:07 ` Jeremy Linton [this message]
2019-01-31 17:55   ` [PATCH v4 09/12] arm64: Use firmware to detect CPUs that are not affected by Spectre-v2 Andre Przywara
2019-01-25 18:07 ` [PATCH v4 10/12] arm64: add sysfs vulnerability show for spectre v2 Jeremy Linton
2019-01-31 17:55   ` Andre Przywara
2019-01-25 18:07 ` [PATCH v4 11/12] arm64: add sysfs vulnerability show for speculative store bypass Jeremy Linton
2019-01-31 17:55   ` Andre Przywara
2019-01-25 18:07 ` [PATCH v4 12/12] arm64: enable generic CPU vulnerabilites support Jeremy Linton
2019-01-31 17:56   ` Andre Przywara
2019-02-08 20:05 ` [PATCH v4 00/12] arm64: add system vulnerability sysfs entries Stefan Wahren

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