[PATCH] parisc: Detect qemu as early as possible in boot process

[PATCH] parisc: Detect qemu as early as possible in boot process

[Helge Deller]

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 <deller@gmx.de>
CC: stable@vger.kernel.org # v4.9+

diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index eb39e7e380d7..841db71958cd 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -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);

diff --git a/arch/parisc/kernel/setup.c b/arch/parisc/kernel/setup.c
index 15dd9e21be7e..d908058d05c1 100644
--- a/arch/parisc/kernel/setup.c
+++ b/arch/parisc/kernel/setup.c
@@ -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();