Revert "s390/smp: rework absolute lowcore access"

This reverts commit 7d06fed.

This introduced vmem_mutex locking from vmem_map_4k_page()
function called from smp_reinit_ipl_cpu() with interrupts
disabled. While it is a pre-SMP early initcall no other CPUs
running in parallel nor other code taking vmem_mutex on this
boot stage - it still needs to be fixed.

Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/boot/startup.c

@@ -10,13 +10,11 @@
 #include <asm/sclp.h>
 #include <asm/diag.h>
 #include <asm/uv.h>
-#include <asm/abs_lowcore.h>
 #include "decompressor.h"
 #include "boot.h"
 #include "uv.h"
 
 unsigned long __bootdata_preserved(__kaslr_offset);
-unsigned long __bootdata_preserved(__abs_lowcore);
 unsigned long __bootdata(__amode31_base);
 unsigned long __bootdata_preserved(VMALLOC_START);
 unsigned long __bootdata_preserved(VMALLOC_END);
@@ -182,8 +180,7 @@ static void setup_kernel_memory_layout(void)
 	/* force vmalloc and modules below kasan shadow */
 	vmax = min(vmax, KASAN_SHADOW_START);
 #endif
-	__abs_lowcore = round_down(vmax - ABS_LOWCORE_MAP_SIZE, sizeof(struct lowcore));
-	MODULES_END = round_down(__abs_lowcore, _SEGMENT_SIZE);
+	MODULES_END = vmax;
 	MODULES_VADDR = MODULES_END - MODULES_LEN;
 	VMALLOC_END = MODULES_VADDR;
 

arch/s390/include/asm/pgtable.h

@@ -1781,8 +1781,6 @@ static inline swp_entry_t __swp_entry(unsigned long type, unsigned long offset)
 
 extern int vmem_add_mapping(unsigned long start, unsigned long size);
 extern void vmem_remove_mapping(unsigned long start, unsigned long size);
-extern int vmem_map_4k_page(unsigned long addr, unsigned long phys, pgprot_t prot);
-extern void vmem_unmap_4k_page(unsigned long addr);
 extern int s390_enable_sie(void);
 extern int s390_enable_skey(void);
 extern void s390_reset_cmma(struct mm_struct *mm);

arch/s390/include/asm/processor.h

@@ -307,6 +307,21 @@ static __always_inline void __noreturn disabled_wait(void)
 #define ARCH_LOW_ADDRESS_LIMIT	0x7fffffffUL
 
 extern int memcpy_real(void *, unsigned long, size_t);
+extern void memcpy_absolute(void *, void *, size_t);
+
+#define put_abs_lowcore(member, x) do {					\
+	unsigned long __abs_address = offsetof(struct lowcore, member);	\
+	__typeof__(((struct lowcore *)0)->member) __tmp = (x);		\
+									\
+	memcpy_absolute(__va(__abs_address), &__tmp, sizeof(__tmp));	\
+} while (0)
+
+#define get_abs_lowcore(x, member) do {					\
+	unsigned long __abs_address = offsetof(struct lowcore, member);	\
+	__typeof__(((struct lowcore *)0)->member) *__ptr = &(x);	\
+									\
+	memcpy_absolute(__ptr, __va(__abs_address), sizeof(*__ptr));	\
+} while (0)
 
 extern int s390_isolate_bp(void);
 extern int s390_isolate_bp_guest(void);

arch/s390/kernel/Makefile

@@ -40,7 +40,7 @@ obj-y	+= sysinfo.o lgr.o os_info.o machine_kexec.o
 obj-y	+= runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o
 obj-y	+= entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o
 obj-y	+= nospec-branch.o ipl_vmparm.o machine_kexec_reloc.o unwind_bc.o
-obj-y	+= smp.o text_amode31.o stacktrace.o abs_lowcore.o
+obj-y	+= smp.o text_amode31.o stacktrace.o
 
 extra-y				+= head64.o vmlinux.lds
 

arch/s390/kernel/ipl.c

@@ -29,7 +29,6 @@
 #include <asm/sclp.h>
 #include <asm/checksum.h>
 #include <asm/debug.h>
-#include <asm/abs_lowcore.h>
 #include <asm/os_info.h>
 #include <asm/sections.h>
 #include <asm/boot_data.h>
@@ -1643,16 +1642,12 @@ static struct shutdown_action __refdata dump_action = {
 static void dump_reipl_run(struct shutdown_trigger *trigger)
 {
 	unsigned long ipib = (unsigned long) reipl_block_actual;
-	struct lowcore *abs_lc;
-	unsigned long flags;
 	unsigned int csum;
 
 	csum = (__force unsigned int)
 	       csum_partial(reipl_block_actual, reipl_block_actual->hdr.len, 0);
-	abs_lc = get_abs_lowcore(&flags);
-	abs_lc->ipib = ipib;
-	abs_lc->ipib_checksum = csum;
-	put_abs_lowcore(abs_lc, flags);
+	put_abs_lowcore(ipib, ipib);
+	put_abs_lowcore(ipib_checksum, csum);
 	dump_run(trigger);
 }
 

arch/s390/kernel/machine_kexec.c

@@ -21,7 +21,6 @@
 #include <asm/elf.h>
 #include <asm/asm-offsets.h>
 #include <asm/cacheflush.h>
-#include <asm/abs_lowcore.h>
 #include <asm/os_info.h>
 #include <asm/set_memory.h>
 #include <asm/stacktrace.h>
@@ -223,18 +222,13 @@ void machine_kexec_cleanup(struct kimage *image)
 
 void arch_crash_save_vmcoreinfo(void)
 {
-	struct lowcore *abs_lc;
-	unsigned long flags;
-
 	VMCOREINFO_SYMBOL(lowcore_ptr);
 	VMCOREINFO_SYMBOL(high_memory);
 	VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS);
 	vmcoreinfo_append_str("SAMODE31=%lx\n", __samode31);
 	vmcoreinfo_append_str("EAMODE31=%lx\n", __eamode31);
 	vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
-	abs_lc = get_abs_lowcore(&flags);
-	abs_lc->vmcore_info = paddr_vmcoreinfo_note();
-	put_abs_lowcore(abs_lc, flags);
+	put_abs_lowcore(vmcore_info, paddr_vmcoreinfo_note());
 }
 
 void machine_shutdown(void)

arch/s390/kernel/os_info.c

@@ -13,7 +13,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <asm/checksum.h>
-#include <asm/abs_lowcore.h>
+#include <asm/lowcore.h>
 #include <asm/os_info.h>
 #include <asm/asm-offsets.h>
 
@@ -57,16 +57,13 @@ void os_info_entry_add(int nr, void *ptr, u64 size)
  */
 void __init os_info_init(void)
 {
-	struct lowcore *abs_lc;
-	unsigned long flags;
+	void *ptr = &os_info;
 
 	os_info.version_major = OS_INFO_VERSION_MAJOR;
 	os_info.version_minor = OS_INFO_VERSION_MINOR;
 	os_info.magic = OS_INFO_MAGIC;
 	os_info.csum = os_info_csum(&os_info);
-	abs_lc = get_abs_lowcore(&flags);
-	abs_lc->os_info = __pa(&os_info);
-	put_abs_lowcore(abs_lc, flags);
+	put_abs_lowcore(os_info, __pa(ptr));
 }
 
 #ifdef CONFIG_CRASH_DUMP

arch/s390/kernel/setup.c

@@ -58,7 +58,7 @@
 #include <asm/smp.h>
 #include <asm/mmu_context.h>
 #include <asm/cpcmd.h>
-#include <asm/abs_lowcore.h>
+#include <asm/lowcore.h>
 #include <asm/nmi.h>
 #include <asm/irq.h>
 #include <asm/page.h>
@@ -411,9 +411,8 @@ void __init arch_call_rest_init(void)
 static void __init setup_lowcore_dat_off(void)
 {
 	unsigned long int_psw_mask = PSW_KERNEL_BITS;
-	struct lowcore *abs_lc, *lc;
 	unsigned long mcck_stack;
-	unsigned long flags;
+	struct lowcore *lc;
 
 	if (IS_ENABLED(CONFIG_KASAN))
 		int_psw_mask |= PSW_MASK_DAT;
@@ -475,13 +474,11 @@ static void __init setup_lowcore_dat_off(void)
 	lc->restart_data = 0;
 	lc->restart_source = -1U;
 
-	abs_lc = get_abs_lowcore(&flags);
-	abs_lc->restart_stack = lc->restart_stack;
-	abs_lc->restart_fn = lc->restart_fn;
-	abs_lc->restart_data = lc->restart_data;
-	abs_lc->restart_source = lc->restart_source;
-	abs_lc->restart_psw = lc->restart_psw;
-	put_abs_lowcore(abs_lc, flags);
+	put_abs_lowcore(restart_stack, lc->restart_stack);
+	put_abs_lowcore(restart_fn, lc->restart_fn);
+	put_abs_lowcore(restart_data, lc->restart_data);
+	put_abs_lowcore(restart_source, lc->restart_source);
+	put_abs_lowcore(restart_psw, lc->restart_psw);
 
 	mcck_stack = (unsigned long)memblock_alloc(THREAD_SIZE, THREAD_SIZE);
 	if (!mcck_stack)
@@ -502,8 +499,8 @@ static void __init setup_lowcore_dat_off(void)
 
 static void __init setup_lowcore_dat_on(void)
 {
-	struct lowcore *abs_lc;
-	unsigned long flags;
+	struct lowcore *lc = lowcore_ptr[0];
+	int cr;
 
 	__ctl_clear_bit(0, 28);
 	S390_lowcore.external_new_psw.mask |= PSW_MASK_DAT;
@@ -512,15 +509,10 @@ static void __init setup_lowcore_dat_on(void)
 	S390_lowcore.io_new_psw.mask |= PSW_MASK_DAT;
 	__ctl_set_bit(0, 28);
 	__ctl_store(S390_lowcore.cregs_save_area, 0, 15);
-	abs_lc = get_abs_lowcore(&flags);
-	abs_lc->restart_flags = RESTART_FLAG_CTLREGS;
-	abs_lc->program_new_psw = S390_lowcore.program_new_psw;
-	memcpy(abs_lc->cregs_save_area, S390_lowcore.cregs_save_area,
-	       sizeof(abs_lc->cregs_save_area));
-	put_abs_lowcore(abs_lc, flags);
-	if (abs_lowcore_map(0, lowcore_ptr[0]))
-		panic("Couldn't setup absolute lowcore");
-	abs_lowcore_mapped = true;
+	put_abs_lowcore(restart_flags, RESTART_FLAG_CTLREGS);
+	put_abs_lowcore(program_new_psw, lc->program_new_psw);
+	for (cr = 0; cr < ARRAY_SIZE(lc->cregs_save_area); cr++)
+		put_abs_lowcore(cregs_save_area[cr], lc->cregs_save_area[cr]);
 }
 
 static struct resource code_resource = {