diff mbox series

[2/4] RISC-V: Implement nosmp commandline option.

Message ID 20190424214801.18880-3-atish.patra@wdc.com (mailing list archive)
State New, archived
Headers show
Series Miscellaneous kernel command line fixes | expand

Commit Message

Atish Patra April 24, 2019, 9:47 p.m. UTC 
nosmp command line option sets max_cpus to zero. No secondary harts
will boot if this is enabled. But present cpu mask will still point to
all possible masks.

Fix present cpu mask for nosmp usecase.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/kernel/smpboot.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Comments

Sudeep Holla April 25, 2019, 9:41 a.m. UTC | #1 
On Wed, Apr 24, 2019 at 02:47:59PM -0700, Atish Patra wrote:
> nosmp command line option sets max_cpus to zero. No secondary harts
> will boot if this is enabled. But present cpu mask will still point to
> all possible masks.
>
> Fix present cpu mask for nosmp usecase.
>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

I just noticed RISC-V has CONFIG_SMP option configurable. ARM64 has
it always on and no option to disable :)

Anyways, this looks good.

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>

--
Regards,
Sudeep
diff mbox series

Patch

diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index eb533b5c2c8c..a8ad200581aa 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -47,6 +47,17 @@  void __init smp_prepare_boot_cpu(void)
 
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
+	int cpuid;
+
+	/* This covers non-smp usecase mandated by "nosmp" option */
+	if (max_cpus == 0)
+		return;
+
+	for_each_possible_cpu(cpuid) {
+		if (cpuid == smp_processor_id())
+			continue;
+		set_cpu_present(cpuid, true);
+	}
 }
 
 void __init setup_smp(void)
@@ -74,7 +85,6 @@  void __init setup_smp(void)
 
 		cpuid_to_hartid_map(cpuid) = hart;
 		set_cpu_possible(cpuid, true);
-		set_cpu_present(cpuid, true);
 		cpuid++;
 	}