kernel/amd64: Add initial LAPIC code

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

3 files changed, 229 insertions, 0 deletions

diff --git a/sys/arch/amd64/amd64/acpi_machdep.c b/sys/arch/amd64/amd64/acpi_machdep.c
index d1686df..3bcdc9d 100644
--- a/sys/arch/amd64/amd64/acpi_machdep.c
+++ b/sys/arch/amd64/amd64/acpi_machdep.c
@@ -33,6 +33,7 @@
 #include <dev/acpi/acpivar.h>
 #include <dev/acpi/tables.h>
 #include <machine/ioapic.h>
+#include <machine/lapic.h>
 
 #define pr_trace(fmt, ...) kprintf("acpi: " fmt, ##__VA_ARGS__)
 
@@ -50,6 +51,7 @@ acpi_init_madt(void)
 
     cur = (uint8_t *)(madt + 1);
     end = (uint8_t *)madt + madt->hdr.length;
+    g_lapic_base = madt->lapic_addr;
 
     while (cur < end) {
         apichdr = (void *)cur;
diff --git a/sys/arch/amd64/amd64/lapic.c b/sys/arch/amd64/amd64/lapic.c
new file mode 100644
index 0000000..f61715d
--- /dev/null
+++ b/sys/arch/amd64/amd64/lapic.c
@@ -0,0 +1,214 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/panic.h>
+#include <sys/mmio.h>
+#include <sys/syslog.h>
+#include <machine/lapicvar.h>
+#include <machine/lapic.h>
+#include <machine/cpuid.h>
+#include <machine/cpu.h>
+#include <machine/msr.h>
+
+#define pr_trace(fmt, ...) kprintf("lapic: " fmt, ##__VA_ARGS__)
+
+/*
+ * Only calls pr_trace if we are the BSP.
+ */
+#define bsp_trace(...) do {                     \
+        uint64_t msr_val;                       \
+                                                \
+        msr_val = rdmsr(IA32_APIC_BASE_MSR);    \
+        if (ISSET(msr_val, BIT(8))) {           \
+            pr_trace(__VA_ARGS__);              \
+        }                                       \
+    } while (0);
+
+uintptr_t g_lapic_base = 0;
+
+/*
+ * Returns true if LAPIC is supported.
+ *
+ * LAPIC is supported if CPUID.(EAX=1H):EDX[9] == 1
+ */
+static inline bool
+lapic_supported(void)
+{
+    uint32_t eax, edx, tmp;
+
+    CPUID(0x00000001, eax, tmp, tmp, edx);
+    return ISSET(edx, BIT(9));
+}
+
+/*
+ * Checks if the processor supports x2APIC
+ * mode. Returns true if so.
+ */
+static inline bool
+lapic_has_x2apic(void)
+{
+    uint32_t ecx, tmp;
+
+    CPUID(0x00000001, tmp, tmp, ecx, tmp);
+    return ISSET(ecx, BIT(21));
+}
+
+/*
+ * Reads a 32 bit value from Local APIC
+ * register space.
+ *
+ * @reg: Register to read from.
+ */
+static inline uint64_t
+lapic_readl(uint32_t reg)
+{
+    void *addr;
+    const struct cpu_info *ci = this_cpu();
+
+    if (!ci->has_x2apic) {
+        addr = (void *)(g_lapic_base + reg);
+        return mmio_read32(addr);
+    } else {
+        reg >>= 4;
+        return rdmsr(x2APIC_MSR_BASE + reg);
+    }
+}
+
+/*
+ * Writes a 32 bit value to Local APIC
+ * register space.
+ *
+ * @reg: Register to write to.
+ */
+static inline void
+lapic_writel(uint32_t reg, uint64_t val)
+{
+    void *addr;
+    const struct cpu_info *ci = this_cpu();
+
+    if (!ci->has_x2apic) {
+        addr = (void *)(g_lapic_base + reg);
+        mmio_write32(addr, val);
+    } else {
+        reg >>= 4;
+        wrmsr(x2APIC_MSR_BASE + reg, val);
+    }
+}
+
+/*
+ * Set bits within a LAPIC register
+ * without overwriting the whole thing.
+ *
+ * @reg: Reg with bits to be set.
+ * @value: Value in reg will be ORd with this.
+ */
+static inline void
+lapic_reg_set(uint32_t reg, uint32_t value)
+{
+    uint32_t old;
+
+    old = lapic_readl(reg);
+    lapic_writel(reg, old | value);
+}
+
+/*
+ * Clear bits within a LAPIC register
+ * without overwriting the whole thing.
+ *
+ * @reg: Reg with bits to be cleared.
+ * @value: Value in reg will be cleared by this value.
+ */
+static inline void
+lapic_reg_clear(uint32_t reg, uint32_t value)
+{
+    uint32_t old;
+
+    old = lapic_readl(reg);
+    lapic_writel(reg, old & ~(value));
+}
+
+/*
+ * Hardware and software enable the Local APIC
+ * through IA32_APIC_BASE_MSR
+ */
+static inline void
+lapic_enable(const struct cpu_info *ci)
+{
+    uint64_t tmp;
+
+    /* Hardware enable the Local APIC */
+    tmp = rdmsr(IA32_APIC_BASE_MSR);
+    tmp |= ci->has_x2apic << x2APIC_ENABLE_SHIFT;
+    wrmsr(IA32_APIC_BASE_MSR, tmp | LAPIC_HW_ENABLE);
+
+    /* Software enable the Local APIC */
+    lapic_reg_set(LAPIC_SVR, LAPIC_SW_ENABLE);
+}
+
+/*
+ * Reads the Local APIC ID of the current
+ * processor.
+ */
+static inline uint32_t
+lapic_read_id(const struct cpu_info *ci)
+{
+    if (!ci->has_x2apic) {
+        return (lapic_readl(LAPIC_ID) >> 24) & 0xF;
+    } else {
+        return lapic_readl(LAPIC_ID);
+    }
+}
+
+void
+lapic_init(void)
+{
+    struct cpu_info *ci = this_cpu();
+
+    /*
+     * Hyra currently depends on the existance
+     * of a Local APIC.
+     */
+    if (!lapic_supported()) {
+        panic("This machine does not support LAPIC!\n");
+    }
+
+    /* Ensure the LAPIC base is valid */
+    if (g_lapic_base == 0) {
+        panic("Invalid LAPIC base\n");
+    }
+
+    ci->has_x2apic = lapic_has_x2apic();
+    lapic_enable(ci);
+
+    ci->apicid = lapic_read_id(ci);
+    bsp_trace("BSP LAPIC enabled in %s mode (id=%d)\n",
+        ci->has_x2apic ? "x2APIC" : "xAPIC", ci->apicid);
+}
diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 275c23e..983a480 100644
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -34,6 +34,7 @@
 #include <machine/trap.h>
 #include <machine/asm.h>
 #include <machine/cpuid.h>
+#include <machine/lapic.h>
 
 #if defined(__SPECTRE_IBRS)
 #define SPECTRE_IBRS  __SPECTRE_IBRS
@@ -76,6 +77,16 @@ try_mitigate_spectre(void)
     ibrs_enable();
 }
 
+/*
+ * Get the descriptor for the currently
+ * running processor.
+ */
+struct cpu_info *
+this_cpu(void)
+{
+    return (void *)amd64_read_gs_base();
+}
+
 void
 cpu_startup(void)
 {
@@ -84,5 +95,7 @@ cpu_startup(void)
 
     setup_vectors();
     amd64_write_gs_base((uintptr_t)&g_bsp_ci);
+
     try_mitigate_spectre();
+    lapic_init();
 }