powerpc/fadump: add support to preserve crash data on FADUMP disabled kernel

Add a new kernel config option, CONFIG_PRESERVE_FA_DUMP that ensures
that crash data, from previously crash'ed kernel, is preserved. This
helps in cases where FADump is not enabled but the subsequent memory
preserving kernel boot is likely to process this crash data. One
typical usecase for this config option is petitboot kernel.

As OPAL allows registering address with it in the first kernel and
retrieving it after MPIPL, use it to store the top of boot memory.
A kernel that intends to preserve crash data retrieves it and avoids
using memory beyond this address.

Move arch_reserved_kernel_pages() function as it is needed for both
FA_DUMP and PRESERVE_FA_DUMP configurations.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/156821375751.5656.11459483669542541602.stgit@hbathini.in.ibm.com

2 files changed, 74 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
index 3e6d6d6d1ec1..2d13e6462339 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -8,6 +8,7 @@ obj-y			+= ultravisor.o
 
 obj-$(CONFIG_SMP)	+= smp.o subcore.o subcore-asm.o
 obj-$(CONFIG_FA_DUMP)	+= opal-fadump.o
+obj-$(CONFIG_PRESERVE_FA_DUMP)	+= opal-fadump.o
 obj-$(CONFIG_PCI)	+= pci.o pci-ioda.o npu-dma.o pci-ioda-tce.o
 obj-$(CONFIG_CXL_BASE)	+= pci-cxl.o
 obj-$(CONFIG_EEH)	+= eeh-powernv.o
diff --git a/arch/powerpc/platforms/powernv/opal-fadump.c b/arch/powerpc/platforms/powernv/opal-fadump.c
index ad4c18bd8809..c66fa96915ae 100644
--- a/arch/powerpc/platforms/powernv/opal-fadump.c
+++ b/arch/powerpc/platforms/powernv/opal-fadump.c
@@ -20,6 +20,67 @@
 
 #include "opal-fadump.h"
 
+
+#ifdef CONFIG_PRESERVE_FA_DUMP
+/*
+ * When dump is active but PRESERVE_FA_DUMP is enabled on the kernel,
+ * ensure crash data is preserved in hope that the subsequent memory
+ * preserving kernel boot is going to process this crash data.
+ */
+void __init opal_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node)
+{
+	const struct opal_fadump_mem_struct *opal_fdm_active;
+	const __be32 *prop;
+	unsigned long dn;
+	u64 addr = 0;
+	s64 ret;
+
+	dn = of_get_flat_dt_subnode_by_name(node, "dump");
+	if (dn == -FDT_ERR_NOTFOUND)
+		return;
+
+	/*
+	 * Check if dump has been initiated on last reboot.
+	 */
+	prop = of_get_flat_dt_prop(dn, "mpipl-boot", NULL);
+	if (!prop)
+		return;
+
+	ret = opal_mpipl_query_tag(OPAL_MPIPL_TAG_KERNEL, &addr);
+	if ((ret != OPAL_SUCCESS) || !addr) {
+		pr_debug("Could not get Kernel metadata (%lld)\n", ret);
+		return;
+	}
+
+	/*
+	 * Preserve memory only if kernel memory regions are registered
+	 * with f/w for MPIPL.
+	 */
+	addr = be64_to_cpu(addr);
+	pr_debug("Kernel metadata addr: %llx\n", addr);
+	opal_fdm_active = (void *)addr;
+	if (opal_fdm_active->registered_regions == 0)
+		return;
+
+	ret = opal_mpipl_query_tag(OPAL_MPIPL_TAG_BOOT_MEM, &addr);
+	if ((ret != OPAL_SUCCESS) || !addr) {
+		pr_err("Failed to get boot memory tag (%lld)\n", ret);
+		return;
+	}
+
+	/*
+	 * Memory below this address can be used for booting a
+	 * capture kernel or petitboot kernel. Preserve everything
+	 * above this address for processing crashdump.
+	 */
+	fadump_conf->boot_mem_top = be64_to_cpu(addr);
+	pr_debug("Preserve everything above %llx\n", fadump_conf->boot_mem_top);
+
+	pr_info("Firmware-assisted dump is active.\n");
+	fadump_conf->dump_active = 1;
+}
+
+#else /* CONFIG_PRESERVE_FA_DUMP */
 static const struct opal_fadump_mem_struct *opal_fdm_active;
 static const struct opal_mpipl_fadump *opal_cpu_metadata;
 static struct opal_fadump_mem_struct *opal_fdm;
@@ -183,6 +244,17 @@ static int opal_fadump_setup_metadata(struct fw_dump *fadump_conf)
 		err = -EPERM;
 	}
 
+	/*
+	 * Register boot memory top address with f/w. Should be retrieved
+	 * by a kernel that intends to preserve crash'ed kernel's memory.
+	 */
+	ret = opal_mpipl_register_tag(OPAL_MPIPL_TAG_BOOT_MEM,
+				      fadump_conf->boot_memory_size);
+	if (ret != OPAL_SUCCESS) {
+		pr_err("Failed to set boot memory tag!\n");
+		err = -EPERM;
+	}
+
 	return err;
 }
 
@@ -649,3 +721,4 @@ void __init opal_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node)
 	fadump_conf->dump_active = 1;
 	opal_fadump_get_config(fadump_conf, opal_fdm_active);
 }
+#endif /* !CONFIG_PRESERVE_FA_DUMP */