s390/dump: rework CPU register dump code

To collect the CPU registers of the crashed system allocated a single
page with memblock_alloc_base and use it as a copy buffer. Replace the
stop-and-store-status sigp with a store-status-at-address sigp in
smp_save_dump_cpus() and smp_store_status(). In both cases the target
CPU is already stopped and store-status-at-address avoids the detour
via the absolute zero page.

For kexec simplify s390_reset_system and call store_status() before
the prefix register of the boot CPU has been set to zero. Use STPX
to store the prefix register and remove dump_prefix_page.

Acked-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 61 insertions, 51 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index d49a8cb404c2..2a69077d482c 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -80,6 +80,10 @@ EXPORT_SYMBOL(smp_cpu_mt_shift);
 unsigned int smp_cpu_mtid;
 EXPORT_SYMBOL(smp_cpu_mtid);
 
+#ifdef CONFIG_CRASH_DUMP
+__vector128 __initdata boot_cpu_vector_save_area[__NUM_VXRS];
+#endif
+
 static unsigned int smp_max_threads __initdata = -1U;
 
 static int __init early_nosmt(char *s)
@@ -105,8 +109,7 @@ DEFINE_MUTEX(smp_cpu_state_mutex);
 /*
  * Signal processor helper functions.
  */
-static inline int __pcpu_sigp_relax(u16 addr, u8 order, unsigned long parm,
-				    u32 *status)
+static inline int __pcpu_sigp_relax(u16 addr, u8 order, unsigned long parm)
 {
 	int cc;
 
@@ -538,53 +541,24 @@ EXPORT_SYMBOL(smp_ctl_clear_bit);
 
 #ifdef CONFIG_CRASH_DUMP
 
-static void __init __smp_store_cpu_state(struct save_area_ext *sa_ext,
-					 u16 address, int is_boot_cpu)
-{
-	void *lc = (void *)(unsigned long) store_prefix();
-	unsigned long vx_sa;
-
-	if (is_boot_cpu) {
-		/* Copy the registers of the boot CPU. */
-		copy_oldmem_kernel(&sa_ext->sa, (void *) __LC_FPREGS_SAVE_AREA,
-				   sizeof(sa_ext->sa));
-		if (MACHINE_HAS_VX)
-			save_vx_regs_safe(sa_ext->vx_regs);
-		return;
-	}
-	/* Get the registers of a non-boot cpu. */
-	__pcpu_sigp_relax(address, SIGP_STOP_AND_STORE_STATUS, 0, NULL);
-	memcpy_real(&sa_ext->sa, lc + __LC_FPREGS_SAVE_AREA, sizeof(sa_ext->sa));
-	if (!MACHINE_HAS_VX)
-		return;
-	/* Get the VX registers */
-	vx_sa = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
-	if (!vx_sa)
-		panic("could not allocate memory for VX save area\n");
-	__pcpu_sigp_relax(address, SIGP_STORE_ADDITIONAL_STATUS, vx_sa, NULL);
-	memcpy(sa_ext->vx_regs, (void *) vx_sa, sizeof(sa_ext->vx_regs));
-	memblock_free(vx_sa, PAGE_SIZE);
-}
-
 int smp_store_status(int cpu)
 {
-	unsigned long vx_sa;
-	struct pcpu *pcpu;
+	struct pcpu *pcpu = pcpu_devices + cpu;
+	unsigned long pa;
 
-	pcpu = pcpu_devices + cpu;
-	if (__pcpu_sigp_relax(pcpu->address, SIGP_STOP_AND_STORE_STATUS,
-			      0, NULL) != SIGP_CC_ORDER_CODE_ACCEPTED)
+	pa = __pa(&pcpu->lowcore->floating_pt_save_area);
+	if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_STATUS_AT_ADDRESS,
+			      pa) != SIGP_CC_ORDER_CODE_ACCEPTED)
 		return -EIO;
 	if (!MACHINE_HAS_VX)
 		return 0;
-	vx_sa = __pa(pcpu->lowcore->vector_save_area_addr);
-	__pcpu_sigp_relax(pcpu->address, SIGP_STORE_ADDITIONAL_STATUS,
-			  vx_sa, NULL);
+	pa = __pa(pcpu->lowcore->vector_save_area_addr);
+	if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_ADDITIONAL_STATUS,
+			      pa) != SIGP_CC_ORDER_CODE_ACCEPTED)
+		return -EIO;
 	return 0;
 }
 
-#endif /* CONFIG_CRASH_DUMP */
-
 /*
  * Collect CPU state of the previous, crashed system.
  * There are four cases:
@@ -593,7 +567,7 @@ int smp_store_status(int cpu)
  *    The state for all CPUs except the boot CPU needs to be collected
  *    with sigp stop-and-store-status. The boot CPU state is located in
  *    the absolute lowcore of the memory stored in the HSA. The zcore code
- *    will allocate the save area and copy the boot CPU state from the HSA.
+ *    will copy the boot CPU state from the HSA.
  * 2) stand-alone kdump for SCSI (zfcp dump with swapped memory)
  *    condition: OLDMEM_BASE != NULL && ipl_info.type == IPL_TYPE_FCP_DUMP
  *    The state for all CPUs except the boot CPU needs to be collected
@@ -611,21 +585,49 @@ int smp_store_status(int cpu)
  *    This case does not exist for s390 anymore, setup_arch explicitly
  *    deactivates the elfcorehdr= kernel parameter
  */
+static __init void smp_save_cpu_vxrs(struct save_area_ext *sa_ext, u16 addr,
+				     bool is_boot_cpu, unsigned long page)
+{
+	__vector128 *vxrs = (__vector128 *) page;
+
+	if (is_boot_cpu)
+		vxrs = boot_cpu_vector_save_area;
+	else
+		__pcpu_sigp_relax(addr, SIGP_STORE_ADDITIONAL_STATUS, page);
+	memcpy(&sa_ext->vx_regs, vxrs, sizeof(sa_ext->vx_regs));
+}
+
+static __init void smp_save_cpu_regs(struct save_area_ext *sa_ext, u16 addr,
+				     bool is_boot_cpu, unsigned long page)
+{
+	void *regs = (void *) page;
+
+	if (is_boot_cpu)
+		copy_oldmem_kernel(regs, (void *) __LC_FPREGS_SAVE_AREA, 512);
+	else
+		__pcpu_sigp_relax(addr, SIGP_STORE_STATUS_AT_ADDRESS, page);
+	memcpy(&sa_ext->sa, regs, sizeof(sa_ext->sa));
+}
+
 void __init smp_save_dump_cpus(void)
 {
-#ifdef CONFIG_CRASH_DUMP
 	int addr, cpu, boot_cpu_addr, max_cpu_addr;
 	struct save_area_ext *sa_ext;
+	unsigned long page;
 	bool is_boot_cpu;
 
 	if (!(OLDMEM_BASE || ipl_info.type == IPL_TYPE_FCP_DUMP))
 		/* No previous system present, normal boot. */
 		return;
+	/* Allocate a page as dumping area for the store status sigps */
+	page = memblock_alloc_base(PAGE_SIZE, PAGE_SIZE, 1UL << 31);
+	if (!page)
+		panic("could not allocate memory for save area\n");
 	/* Set multi-threading state to the previous system. */
 	pcpu_set_smt(sclp.mtid_prev);
 	max_cpu_addr = SCLP_MAX_CORES << sclp.mtid_prev;
 	for (cpu = 0, addr = 0; addr <= max_cpu_addr; addr++) {
-		if (__pcpu_sigp_relax(addr, SIGP_SENSE, 0, NULL) ==
+		if (__pcpu_sigp_relax(addr, SIGP_SENSE, 0) ==
 		    SIGP_CC_NOT_OPERATIONAL)
 			continue;
 		cpu += 1;
@@ -634,7 +636,7 @@ void __init smp_save_dump_cpus(void)
 	dump_save_areas.count = cpu;
 	boot_cpu_addr = stap();
 	for (cpu = 0, addr = 0; addr <= max_cpu_addr; addr++) {
-		if (__pcpu_sigp_relax(addr, SIGP_SENSE, 0, NULL) ==
+		if (__pcpu_sigp_relax(addr, SIGP_SENSE, 0) ==
 		    SIGP_CC_NOT_OPERATIONAL)
 			continue;
 		sa_ext = (void *) memblock_alloc(sizeof(*sa_ext), 8);
@@ -643,16 +645,24 @@ void __init smp_save_dump_cpus(void)
 			panic("could not allocate memory for save area\n");
 		is_boot_cpu = (addr == boot_cpu_addr);
 		cpu += 1;
-		if (is_boot_cpu && !OLDMEM_BASE)
-			/* Skip boot CPU for standard zfcp dump. */
-			continue;
-		/* Get state for this CPU. */
-		__smp_store_cpu_state(sa_ext, addr, is_boot_cpu);
+		if (MACHINE_HAS_VX)
+			/* Get the vector registers */
+			smp_save_cpu_vxrs(sa_ext, addr, is_boot_cpu, page);
+		/*
+		 * For a zfcp dump OLDMEM_BASE == NULL and the registers
+		 * of the boot CPU are stored in the HSA. To retrieve
+		 * these registers an SCLP request is required which is
+		 * done by drivers/s390/char/zcore.c:init_cpu_info()
+		 */
+		if (!is_boot_cpu || OLDMEM_BASE)
+			/* Get the CPU registers */
+			smp_save_cpu_regs(sa_ext, addr, is_boot_cpu, page);
 	}
+	memblock_free(page, PAGE_SIZE);
 	diag308_reset();
 	pcpu_set_smt(0);
-#endif /* CONFIG_CRASH_DUMP */
 }
+#endif /* CONFIG_CRASH_DUMP */
 
 void smp_cpu_set_polarization(int cpu, int val)
 {
@@ -676,7 +686,7 @@ static struct sclp_core_info *smp_get_core_info(void)
 		for (address = 0;
 		     address < (SCLP_MAX_CORES << smp_cpu_mt_shift);
 		     address += (1U << smp_cpu_mt_shift)) {
-			if (__pcpu_sigp_relax(address, SIGP_SENSE, 0, NULL) ==
+			if (__pcpu_sigp_relax(address, SIGP_SENSE, 0) ==
 			    SIGP_CC_NOT_OPERATIONAL)
 				continue;
 			info->core[info->configured].core_id =