1 files changed, 95 insertions, 0 deletions
diff --git a/arch/s390/kernel/abs_lowcore.c b/arch/s390/kernel/abs_lowcore.c
new file mode 100644
index 000000000000..fb92e8ed0525
--- /dev/null
+++ b/arch/s390/kernel/abs_lowcore.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/pgtable.h>
+#include <asm/abs_lowcore.h>
+
+#define ABS_LOWCORE_UNMAPPED	1
+#define ABS_LOWCORE_LAP_ON	2
+#define ABS_LOWCORE_IRQS_ON	4
+
+unsigned long __bootdata_preserved(__abs_lowcore);
+bool __ro_after_init abs_lowcore_mapped;
+
+int abs_lowcore_map(int cpu, struct lowcore *lc, bool alloc)
+{
+	unsigned long addr = __abs_lowcore + (cpu * sizeof(struct lowcore));
+	unsigned long phys = __pa(lc);
+	int rc, i;
+
+	for (i = 0; i < LC_PAGES; i++) {
+		rc = __vmem_map_4k_page(addr, phys, PAGE_KERNEL, alloc);
+		if (rc) {
+			/*
+			 * Do not unmap allocated page tables in case the
+			 * allocation was not requested. In such a case the
+			 * request is expected coming from an atomic context,
+			 * while the unmap attempt might sleep.
+			 */
+			if (alloc) {
+				for (--i; i >= 0; i--) {
+					addr -= PAGE_SIZE;
+					vmem_unmap_4k_page(addr);
+				}
+			}
+			return rc;
+		}
+		addr += PAGE_SIZE;
+		phys += PAGE_SIZE;
+	}
+	return 0;
+}
+
+void abs_lowcore_unmap(int cpu)
+{
+	unsigned long addr = __abs_lowcore + (cpu * sizeof(struct lowcore));
+	int i;
+
+	for (i = 0; i < LC_PAGES; i++) {
+		vmem_unmap_4k_page(addr);
+		addr += PAGE_SIZE;
+	}
+}
+
+struct lowcore *get_abs_lowcore(unsigned long *flags)
+{
+	unsigned long irq_flags;
+	union ctlreg0 cr0;
+	int cpu;
+
+	*flags = 0;
+	cpu = get_cpu();
+	if (abs_lowcore_mapped) {
+		return ((struct lowcore *)__abs_lowcore) + cpu;
+	} else {
+		if (cpu != 0)
+			panic("Invalid unmapped absolute lowcore access\n");
+		local_irq_save(irq_flags);
+		if (!irqs_disabled_flags(irq_flags))
+			*flags |= ABS_LOWCORE_IRQS_ON;
+		__ctl_store(cr0.val, 0, 0);
+		if (cr0.lap) {
+			*flags |= ABS_LOWCORE_LAP_ON;
+			__ctl_clear_bit(0, 28);
+		}
+		*flags |= ABS_LOWCORE_UNMAPPED;
+		return lowcore_ptr[0];
+	}
+}
+
+void put_abs_lowcore(struct lowcore *lc, unsigned long flags)
+{
+	if (abs_lowcore_mapped) {
+		if (flags)
+			panic("Invalid mapped absolute lowcore release\n");
+	} else {
+		if (smp_processor_id() != 0)
+			panic("Invalid mapped absolute lowcore access\n");
+		if (!(flags & ABS_LOWCORE_UNMAPPED))
+			panic("Invalid unmapped absolute lowcore release\n");
+		if (flags & ABS_LOWCORE_LAP_ON)
+			__ctl_set_bit(0, 28);
+		if (flags & ABS_LOWCORE_IRQS_ON)
+			local_irq_enable();
+	}
+	put_cpu();
+}