From f290314f286b70a8f59becedd5f789c21f675b5d Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Thu, 20 Jun 2024 20:35:38 -0400
Subject: kernel/amd64: intr: Add splraise/splx support

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/amd64/intr.c   | 63 ++++++++++++++++++++++++++++++++++++++++---
 sys/arch/amd64/amd64/lapic.c  |  2 +-
 sys/include/arch/amd64/asm.h  | 14 ++++++++++
 sys/include/arch/amd64/cpu.h  |  1 +
 sys/include/arch/amd64/intr.h | 19 ++++++++++++-
 5 files changed, 93 insertions(+), 6 deletions(-)

(limited to 'sys')

diff --git a/sys/arch/amd64/amd64/intr.c b/sys/arch/amd64/amd64/intr.c
index b841da7..3e3f309 100644
--- a/sys/arch/amd64/amd64/intr.c
+++ b/sys/arch/amd64/amd64/intr.c
@@ -28,16 +28,71 @@
  */
 
 #include <sys/types.h>
+#include <sys/param.h>
+#include <sys/errno.h>
+#include <sys/panic.h>
 #include <machine/intr.h>
+#include <machine/cpu.h>
+#include <machine/asm.h>
+#include <vm/dynalloc.h>
+
+static struct intr_entry *intrs[256] = {0};
+
+void
+splraise(uint8_t s)
+{
+    struct cpu_info *ci = this_cpu();
+
+    if (s < ci->ipl) {
+        panic("splraise IPL less than current IPL\n");
+    }
+
+    amd64_write_cr8(s);
+    ci->ipl = s;
+}
+
+void
+splx(uint8_t s)
+{
+    struct cpu_info *ci = this_cpu();
+
+    if (s > ci->ipl) {
+        panic("splx IPL greater than current IPL\n");
+    }
+
+    amd64_write_cr8(s);
+    ci->ipl = s;
+}
 
 int
-intr_alloc_vector(void)
+intr_alloc_vector(const char *name, uint8_t priority)
 {
-    static size_t vec = 0x21;
+    size_t vec = MAX(priority << IPL_SHIFT, 0x20);
+    struct intr_entry *intr;
 
-    if (vec >= 0xFF) {
+    /* Sanity check */
+    if (vec > NELEM(intrs)) {
         return -1;
     }
 
-    return vec++;
+    /*
+     * Try to allocate an interrupt vector. An IPL is made up
+     * of 4 bits so there can be 16 vectors per IPL.
+     */
+    for (int i = vec; i < vec + 16; ++i) {
+        if (intrs[i] != NULL) {
+            continue;
+        }
+
+        intr = dynalloc(sizeof(*intr));
+        if (intr == NULL) {
+            return -ENOMEM;
+        }
+
+        intr->priority = priority;
+        intrs[i] = intr;
+        return i;
+    }
+
+    return -1;
 }
diff --git a/sys/arch/amd64/amd64/lapic.c b/sys/arch/amd64/amd64/lapic.c
index b7cefd4..896c2bd 100644
--- a/sys/arch/amd64/amd64/lapic.c
+++ b/sys/arch/amd64/amd64/lapic.c
@@ -317,7 +317,7 @@ lapic_init(void)
 
     /* Allocate a vector if needed */
     if (lapic_timer_vec == 0) {
-        lapic_timer_vec = intr_alloc_vector();
+        lapic_timer_vec = intr_alloc_vector("lapictmr", IPL_CLOCK);
         idt_set_desc(lapic_timer_vec, IDT_INT_GATE, ISR(lapic_tmr_isr),
             IST_SCHED);
     }
diff --git a/sys/include/arch/amd64/asm.h b/sys/include/arch/amd64/asm.h
index d7334fe..e85dd87 100644
--- a/sys/include/arch/amd64/asm.h
+++ b/sys/include/arch/amd64/asm.h
@@ -84,6 +84,20 @@ amd64_write_cr0(uint64_t val)
     __ASMV("mov %0, %%cr0" :: "r" (val) : "memory");
 }
 
+static inline uint64_t
+amd64_read_cr8(void)
+{
+    uint64_t cr8;
+    __ASMV("mov %%cr8, %0" : "=r" (cr8) :: "memory");
+    return cr8;
+}
+
+static inline void
+amd64_write_cr8(uint64_t val)
+{
+    __ASMV("mov %0, %%cr8" :: "r" (val) : "memory");
+}
+
 static inline uint64_t
 amd64_read_cr4(void)
 {
diff --git a/sys/include/arch/amd64/cpu.h b/sys/include/arch/amd64/cpu.h
index b5420a6..16936e9 100644
--- a/sys/include/arch/amd64/cpu.h
+++ b/sys/include/arch/amd64/cpu.h
@@ -38,6 +38,7 @@
 struct cpu_info {
     uint32_t apicid;
     uint8_t has_x2apic : 1;
+    uint8_t ipl;
     size_t lapic_tmr_freq;
     struct tss_entry *tss;
     struct proc *curtd;
diff --git a/sys/include/arch/amd64/intr.h b/sys/include/arch/amd64/intr.h
index 3f0da77..af5edf2 100644
--- a/sys/include/arch/amd64/intr.h
+++ b/sys/include/arch/amd64/intr.h
@@ -36,6 +36,23 @@
 #define IST_HW_IRQ  2U
 #define IST_SW_INT  3U
 
-int intr_alloc_vector(void);
+/* Upper 4 bits of interrupt vector */
+#define IPL_SHIFT 4
+
+/*
+ * Interrupt priority levels
+ */
+#define IPL_NONE    0   /* Don't defer anything */
+#define IPL_BIO     1   /* Block I/O */
+#define IPL_CLOCK   2   /* Clock */
+#define IPL_HIGH    3   /* Defer everything */
+
+struct intr_entry {
+    int priority;
+};
+
+int intr_alloc_vector(const char *name, uint8_t priority);
+void splraise(uint8_t s);
+void splx(uint8_t s);
 
 #endif
-- 
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