parisc: Detect qemu as early as possible in boot process

PATCH New Helge Deller 1 participant 1 message Apr 2, 2019 PA-RISC architecture

Share & tools

Helge Deller

author maintainer

2019-04-02 10:13 UTC #0 lore raw

PATCH 1/1 parisc: Detect qemu as early as possible in boot process

While adding LASI support to qemu, I noticed that the qemu detection in the kernel happens much too late. For example, when a LASI chip is found by the kernel, it registers the LASI LED driver as well. But when we run on qemu it makes sense to avoid spending unneccesary CPU cycles, so we need to access the running_on_qemu flag earlier as before.

This patch now makes the qemu detection the fist task of the Linux kernel by moving it to where the kernel enters the C-coding.

Fixes 310d82784fb4 ("parisc: qemu idle sleep support")

Signed-off-by Helge Deller <[email protected]>

CC [email protected] # v4.9+

arch/parisc/kernel/process.c +0 -6

index eb39e7e380d7..841db71958cd 100644
@@ -210,12 +210,6 @@ void __cpuidle arch_cpu_idle(void)
 
 static int __init parisc_idle_init(void)
 {
-	const char *marker;
-
-	/* check QEMU/SeaBIOS marker in PAGE0 */
-	marker = (char *) &PAGE0->pad0;
-	running_on_qemu = (memcmp(marker, "SeaBIOS", 8) == 0);
-
 	if (!running_on_qemu)
 		cpu_idle_poll_ctrl(1);

arch/parisc/kernel/setup.c +3 -0

index 15dd9e21be7e..d908058d05c1 100644
@@ -397,6 +397,9 @@ void __init start_parisc(void)
 	int ret, cpunum;
 	struct pdc_coproc_cfg coproc_cfg;
 
+	/* check QEMU/SeaBIOS marker in PAGE0 */
+	running_on_qemu = (memcmp(&PAGE0->pad0, "SeaBIOS", 8) == 0);
+
 	cpunum = smp_processor_id();
 
 	init_cpu_topology();