[PATCH 1/2] arm64: psci: respect MIGRATE_INFO_TYPE

[mark.rutland@arm.com (Mark Rutland)]

Commit e71246a23acb (PSCI: Add initial support for PSCIv0.2 functions)
added hooks for MIGRATE_INFO_TYPE, but didn't call it anywhere. This
means that currently a UP Trusted OS can reject CPU_OFF calls, which
will cause things to blow up.

This patch ensures we test MIGRATE_INFO_TYPE before calling CPU_OFF. If
there's a UP trusted OS hotplug is rejected. Full support for PSCI in
the presence of a UP trusted OS will require the use of MIGRATE and will
have to come as a later patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/kernel/psci.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 5539547..a5407af 100644
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -386,6 +386,20 @@ static int cpu_psci_cpu_disable(unsigned int cpu)
 	/* Fail early if we don't have CPU_OFF support */
 	if (!psci_ops.cpu_off)
 		return -EOPNOTSUPP;
+
+	/*
+	 * In the presence of a UP trusted OS, it might not be possible to
+	 * hotplug certain CPUs, and CPU_OFF may return (which would be bad).
+	 * Supporting a UP trusted OS requires careful use of
+	 * MIGRATE_INFO_UP_CPU and MIGRATE, so for now fail in the presence of
+	 * a UP Trusted OS.
+	 */
+	if (psci_ops.migrate_info_type &&
+		psci_ops.migrate_info_type() != PSCI_0_2_TOS_MP) {
+			pr_warn("Unable to handle UP trusted OS\n");
+			return -EPERM;
+	}
+
 	return 0;
 }
 
-- 
1.9.1