-----Original Message-----
From: Russell King <redacted> On Behalf Of Russell King
Sent: 2023年10月24日 23:19
To: linux-pm@vger.kernel.org; loongarch@lists.linux.dev;
linux-acpi@vger.kernel.org; linux-arch@vger.kernel.org;
linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
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linux-ia64@vger.kernel.org; linux-parisc@vger.kernel.org
Cc: Salil Mehta <redacted>; Jean-Philippe Brucker
[off-list ref]; Jianyong Wu [off-list ref]; Justin He
[off-list ref]; James Morse [off-list ref]; Catalin
Marinas [off-list ref]; Will Deacon [off-list ref]; Mark
Rutland [off-list ref]; Lorenzo Pieralisi [off-list ref]
Subject: [PATCH 34/39] arm64: psci: Ignore DENIED CPUs

From: Jean-Philippe Brucker <redacted>

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.

See https://developer.arm.com/documentation/den0022/f/?lang=en page 58.

Signed-off-by: Jean-Philippe Brucker <redacted> [ morse:
Rewrote commit message ]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Russell King (Oracle) <redacted>
---
Changes since RFC v2
 * Add specification reference
 * Use EPERM rather than EPROBE_DEFER
---
 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..68ec7fbe166f 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 != -EPERM)
+			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..ee82e7880d8c 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 -EPERM;
 	return psci_to_linux_errno(err);
 }

--
2.30.2