arm64: psci: Ignore DENIED CPUs

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.

Note the alternatives to the PSCI cpu_boot() callback do not
return -EPERM so the change in smp.c has no affect.

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: Gavin Shan <gshan@redhat.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240529133446.28446-16-Jonathan.Cameron@huawei.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 29a8e444db836a70a17fecf2794f358a5f8f3003..fabd732d0a2dfee37074ef4ebb6ce5894871c8bd 100644 (file)
--- 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 6b0572daa9dab85f09356e6ae52a92350c1876de..a755b9f902fab704911750ed2db4d7e074eae65b 100644 (file)
--- 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;
        }