Revert "s390/smp: rework absolute lowcore access"

This reverts commit 7d06fed77b7d8fc9f6cc41b4e3f2823d32532ad8.

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>

3 files changed, 38 insertions, 116 deletions

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 7b6873ac99d1..6a0ac00d5a42 100644
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -38,7 +38,7 @@
 #include <asm/kfence.h>
 #include <asm/ptdump.h>
 #include <asm/dma.h>
-#include <asm/abs_lowcore.h>
+#include <asm/lowcore.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/sections.h>
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index b8451ddbb3d6..d6d84e02f35a 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -15,7 +15,6 @@
 #include <asm/asm-extable.h>
 #include <asm/ctl_reg.h>
 #include <asm/io.h>
-#include <asm/abs_lowcore.h>
 #include <asm/stacktrace.h>
 
 static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
@@ -149,20 +148,46 @@ int memcpy_real(void *dest, unsigned long src, size_t count)
 }
 
 /*
- * Find CPU that owns swapped prefix page
+ * Copy memory in absolute mode (kernel to kernel)
  */
-static int get_swapped_owner(phys_addr_t addr)
+void memcpy_absolute(void *dest, void *src, size_t count)
+{
+	unsigned long cr0, flags, prefix;
+
+	flags = arch_local_irq_save();
+	__ctl_store(cr0, 0, 0);
+	__ctl_clear_bit(0, 28); /* disable lowcore protection */
+	prefix = store_prefix();
+	if (prefix) {
+		local_mcck_disable();
+		set_prefix(0);
+		memcpy(dest, src, count);
+		set_prefix(prefix);
+		local_mcck_enable();
+	} else {
+		memcpy(dest, src, count);
+	}
+	__ctl_load(cr0, 0, 0);
+	arch_local_irq_restore(flags);
+}
+
+/*
+ * Check if physical address is within prefix or zero page
+ */
+static int is_swapped(phys_addr_t addr)
 {
 	phys_addr_t lc;
 	int cpu;
 
+	if (addr < sizeof(struct lowcore))
+		return 1;
 	for_each_online_cpu(cpu) {
 		lc = virt_to_phys(lowcore_ptr[cpu]);
 		if (addr > lc + sizeof(struct lowcore) - 1 || addr < lc)
 			continue;
-		return cpu;
+		return 1;
 	}
-	return -1;
+	return 0;
 }
 
 /*
@@ -175,35 +200,17 @@ void *xlate_dev_mem_ptr(phys_addr_t addr)
 {
 	void *ptr = phys_to_virt(addr);
 	void *bounce = ptr;
-	struct lowcore *abs_lc;
-	unsigned long flags;
 	unsigned long size;
-	int this_cpu, cpu;
 
 	cpus_read_lock();
-	this_cpu = get_cpu();
-	if (addr >= sizeof(struct lowcore)) {
-		cpu = get_swapped_owner(addr);
-		if (cpu < 0)
-			goto out;
-	}
-	bounce = (void *)__get_free_page(GFP_ATOMIC);
-	if (!bounce)
-		goto out;
-	size = PAGE_SIZE - (addr & ~PAGE_MASK);
-	if (addr < sizeof(struct lowcore)) {
-		abs_lc = get_abs_lowcore(&flags);
-		ptr = (void *)abs_lc + addr;
-		memcpy(bounce, ptr, size);
-		put_abs_lowcore(abs_lc, flags);
-	} else if (cpu == this_cpu) {
-		ptr = (void *)(addr - virt_to_phys(lowcore_ptr[cpu]));
-		memcpy(bounce, ptr, size);
-	} else {
-		memcpy(bounce, ptr, size);
+	preempt_disable();
+	if (is_swapped(addr)) {
+		size = PAGE_SIZE - (addr & ~PAGE_MASK);
+		bounce = (void *) __get_free_page(GFP_ATOMIC);
+		if (bounce)
+			memcpy_absolute(bounce, ptr, size);
 	}
-out:
-	put_cpu();
+	preempt_enable();
 	cpus_read_unlock();
 	return bounce;
 }
diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index 203ba2bfea59..c2583f921ca8 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -561,91 +561,6 @@ int vmem_add_mapping(unsigned long start, unsigned long size)
 }
 
 /*
- * Allocate new or return existing page-table entry, but do not map it
- * to any physical address. If missing, allocate segment- and region-
- * table entries along. Meeting a large segment- or region-table entry
- * while traversing is an error, since the function is expected to be
- * called against virtual regions reserverd for 4KB mappings only.
- */
-static pte_t *vmem_get_alloc_pte(unsigned long addr)
-{
-	pte_t *ptep = NULL;
-	pgd_t *pgd;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
-
-	pgd = pgd_offset_k(addr);
-	if (pgd_none(*pgd)) {
-		p4d = vmem_crst_alloc(_REGION2_ENTRY_EMPTY);
-		if (!p4d)
-			goto out;
-		pgd_populate(&init_mm, pgd, p4d);
-	}
-	p4d = p4d_offset(pgd, addr);
-	if (p4d_none(*p4d)) {
-		pud = vmem_crst_alloc(_REGION3_ENTRY_EMPTY);
-		if (!pud)
-			goto out;
-		p4d_populate(&init_mm, p4d, pud);
-	}
-	pud = pud_offset(p4d, addr);
-	if (pud_none(*pud)) {
-		pmd = vmem_crst_alloc(_SEGMENT_ENTRY_EMPTY);
-		if (!pmd)
-			goto out;
-		pud_populate(&init_mm, pud, pmd);
-	} else if (WARN_ON_ONCE(pud_large(*pud))) {
-		goto out;
-	}
-	pmd = pmd_offset(pud, addr);
-	if (pmd_none(*pmd)) {
-		pte = vmem_pte_alloc();
-		if (!pte)
-			goto out;
-		pmd_populate(&init_mm, pmd, pte);
-	} else if (WARN_ON_ONCE(pmd_large(*pmd))) {
-		goto out;
-	}
-	ptep = pte_offset_kernel(pmd, addr);
-out:
-	return ptep;
-}
-
-int vmem_map_4k_page(unsigned long addr, unsigned long phys, pgprot_t prot)
-{
-	pte_t *ptep, pte;
-	int rc = 0;
-
-	if (!IS_ALIGNED(addr, PAGE_SIZE))
-		return -EINVAL;
-	mutex_lock(&vmem_mutex);
-	ptep = vmem_get_alloc_pte(addr);
-	if (!ptep) {
-		rc = -ENOMEM;
-		goto out;
-	}
-	__ptep_ipte(addr, ptep, 0, 0, IPTE_GLOBAL);
-	pte = mk_pte_phys(phys, prot);
-	set_pte(ptep, pte);
-out:
-	mutex_unlock(&vmem_mutex);
-	return rc;
-}
-
-void vmem_unmap_4k_page(unsigned long addr)
-{
-	pte_t *ptep;
-
-	mutex_lock(&vmem_mutex);
-	ptep = virt_to_kpte(addr);
-	__ptep_ipte(addr, ptep, 0, 0, IPTE_GLOBAL);
-	pte_clear(&init_mm, addr, ptep);
-	mutex_unlock(&vmem_mutex);
-}
-
-/*
  * map whole physical memory to virtual memory (identity mapping)
  * we reserve enough space in the vmalloc area for vmemmap to hotplug
  * additional memory segments.