Re: [PATCH v7 12/16] arm64: psci: Ignore DENIED CPUs

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On 4/18/24 23:54, Jonathan Cameron wrote:
From: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>

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

See page 58.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
[ morse: Rewrote commit message ]
Signed-off-by: James Morse <james.morse@xxxxxxx>
Tested-by: Miguel Luis <miguel.luis@xxxxxxxxxx>
Tested-by: Vishnu Pajjuri <vishnu@xxxxxxxxxxxxxxxxxxxxxx>
Tested-by: Jianyong Wu <jianyong.wu@xxxxxxx>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
v7: No change
  arch/arm64/kernel/psci.c | 2 +-
  arch/arm64/kernel/smp.c  | 3 ++-
  2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 29a8e444db83..fabd732d0a2d 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 != -EPERM)
  		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 4ced34f62dab..dc0e0b3ec2d4 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -132,7 +132,8 @@ 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;

The changes in smp.c are based the assumption that PSCI is the only backend, which
isn't true. So we probably need move this error message to specific backend, which
could be PSCI, ACPI parking protocol, or smp_spin_table.


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