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Subject[PATCH v6 12/16] arm64: psci: Ignore DENIED CPUs
Date
From: Jean-Philippe Brucker <jean-philippe@linaro.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.

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

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
[ morse: Rewrote commit message ]
Signed-off-by: James Morse <james.morse@arm.com>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu@arm.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
v5: 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;
}

--
2.39.2

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