linux-kernel - [RFC PATCH v2 31/35] arm64: psci: Ignore DENIED CPUs

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Message-Id: <20230913163823.7880-32-james.morse@arm.com>
Date:   Wed, 13 Sep 2023 16:38:19 +0000
From:   James Morse <james.morse@....com>
To:     linux-pm@...r.kernel.org, loongarch@...ts.linux.dev,
        linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, kvmarm@...ts.linux.dev
Cc:     x86@...nel.org, Salil Mehta <salil.mehta@...wei.com>,
        Russell King <linux@...linux.org.uk>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        jianyong.wu@....com, justin.he@....com
Subject: [RFC PATCH v2 31/35] arm64: psci: Ignore DENIED CPUs

From: Jean-Philippe Brucker <jean-philippe@...aro.org>

When a CPU is marked as disabled, but online capable in the MADT, PSCI
applies some firmware policy to control when it can be brought online.
PSCI returns DENIED to a CPU_ON request if this is not currently
permitted. The OS can learn the current policy from the _STA enabled bit.

Handle the PSCI DENIED return code gracefully instead of printing an
error.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
[ morse: Rewrote commit message ]
Signed-off-by: James Morse <james.morse@....com>
---
 arch/arm64/kernel/psci.c     | 2 +-
 arch/arm64/kernel/smp.c      | 3 ++-
 drivers/firmware/psci/psci.c | 2 ++
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 29a8e444db83..4fcc0cdd757b 100644
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -40,7 +40,7 @@ static int cpu_psci_cpu_boot(unsigned int cpu)
 {
 	phys_addr_t pa_secondary_entry = __pa_symbol(secondary_entry);
 	int err = psci_ops.cpu_on(cpu_logical_map(cpu), pa_secondary_entry);
-	if (err)
+	if (err && err != -EPROBE_DEFER)
 		pr_err("failed to boot CPU%d (%d)\n", cpu, err);
 
 	return err;
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 8c8f55721786..e958db987665 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -124,7 +124,8 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	/* Now bring the CPU into our world */
 	ret = boot_secondary(cpu, idle);
 	if (ret) {
-		pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
+		if (ret != -EPROBE_DEFER)
+			pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
 		return ret;
 	}
 
diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index d9629ff87861..f7ab3fed3528 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -218,6 +218,8 @@ static int __psci_cpu_on(u32 fn, unsigned long cpuid, unsigned long entry_point)
 	int err;
 
 	err = invoke_psci_fn(fn, cpuid, entry_point, 0);
+	if (err == PSCI_RET_DENIED)
+		return -EPROBE_DEFER;
 	return psci_to_linux_errno(err);
 }
 
-- 
2.39.2