kernel/amd64: Add preemptable flag to cpu_info

Add a new 'preempt' field to cpu_info' to indicate if that specific processor is preemptable.

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 6 insertions, 0 deletions

diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 94b2d18..72de150 100644
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -609,6 +609,7 @@ cpu_startup(struct cpu_info *ci)
 
     try_mitigate_spectre();
     ci->online = 1;
+    ci->preempt  = 1;
 
     cpu_get_info(ci);
     cpu_enable_smep();
diff --git a/sys/arch/amd64/amd64/proc_machdep.c b/sys/arch/amd64/amd64/proc_machdep.c
index a1d6563..56348be 100644
--- a/sys/arch/amd64/amd64/proc_machdep.c
+++ b/sys/arch/amd64/amd64/proc_machdep.c
@@ -273,6 +273,11 @@ md_sched_switch(struct trapframe *tf)
     struct cpu_info *ci;
 
     ci = this_cpu();
+    if (!ci->preempt) {
+        sched_oneshot(false);
+        return;
+    }
+
     td = ci->curtd;
     mi_sched_switch(td);