kernel/amd64: lapic: Add ESR reading logic

Signed-off-by: sigsegv7 <ian@vegaa.systems>

1 files changed, 21 insertions, 0 deletions

diff --git a/sys/arch/amd64/lapic.c b/sys/arch/amd64/lapic.c
index af219d2..6f2f6c1 100644
--- a/sys/arch/amd64/lapic.c
+++ b/sys/arch/amd64/lapic.c
@@ -208,6 +208,27 @@ lapic_set_ldr(void)
         lapic_writel(LAPIC_LDR, LAPIC_STARTUP_LID);
 }
 
+/*
+ * Reads the Local APIC error status
+ * register. Returns the value read.
+ *
+ * XXX: It is a good idea to save the value returned as
+ *      each read will clear the register.
+ */
+static inline uint32_t
+lapic_read_esr(void)
+{
+    /*
+     * We'll need to write 0 to clear the ESR and reload
+     * it with any new errors that happened... In xAPIC mode
+     * we can write anything to do this; however, in x2APIC
+     * mode, writes of 0 are enforced. We'll only write 0 to
+     * work both with x2APIC and xAPIC mode...
+     */
+    lapic_writel(LAPIC_ERR, 0);
+    return lapic_readl(LAPIC_ERR);
+}
+
 void
 lapic_timer_init(size_t *freq_out)
 {