powerpc/fadump: save CPU reg data in vmcore when PHYP terminates LPAR

An LPAR can be terminated by the POWER Hypervisor (PHYP) for various
reasons. If FADump was configured when PHYP terminates the LPAR,
platform-assisted dump is initiated to save the kernel dump. But CPU
register data would not be processed/saved in the vmcore in such case
because CPU mask is set in crash_fadump() at the time of kernel crash
and it remains unset in this case with LPAR being terminated by PHYP
abruptly.

To get around the problem, initialize cpu_mask to cpu_possible_mask
so as to ensure all possible CPUs' register data is processed for the
vmcore generated on PHYP terminated LPAR. Also, rename the crash info
member variable from online_mask to cpu_mask as it doesn't necessarily
have to be online CPU mask always.
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220404182137.59231-1-hbathini@linux.ibm.com

arch/powerpc/include/asm/fadump-internal.h

@@ -50,7 +50,7 @@ struct fadump_crash_info_header {
 	u64		elfcorehdr_addr;
 	u32		crashing_cpu;
 	struct pt_regs	regs;
-	struct cpumask	online_mask;
+	struct cpumask	cpu_mask;
 };
 
 struct fadump_memory_range {

arch/powerpc/kernel/fadump.c

@@ -728,7 +728,7 @@ void crash_fadump(struct pt_regs *regs, const char *str)
 	else
 		ppc_save_regs(&fdh->regs);
 
-	fdh->online_mask = *cpu_online_mask;
+	fdh->cpu_mask = *cpu_online_mask;
 
 	/*
 	 * If we came in via system reset, wait a while for the secondary
@@ -1164,6 +1164,11 @@ static unsigned long init_fadump_header(unsigned long addr)
 	fdh->elfcorehdr_addr = addr;
 	/* We will set the crashing cpu id in crash_fadump() during crash. */
 	fdh->crashing_cpu = FADUMP_CPU_UNKNOWN;
+	/*
+	 * When LPAR is terminated by PYHP, ensure all possible CPUs'
+	 * register data is processed while exporting the vmcore.
+	 */
+	fdh->cpu_mask = *cpu_possible_mask;
 
 	return addr;
 }

arch/powerpc/platforms/pseries/rtas-fadump.c

@@ -351,7 +351,7 @@ static int __init rtas_fadump_build_cpu_notes(struct fw_dump *fadump_conf)
 		/* Lower 4 bytes of reg_value contains logical cpu id */
 		cpu = (be64_to_cpu(reg_entry->reg_value) &
 		       RTAS_FADUMP_CPU_ID_MASK);
-		if (fdh && !cpumask_test_cpu(cpu, &fdh->online_mask)) {
+		if (fdh && !cpumask_test_cpu(cpu, &fdh->cpu_mask)) {
 			RTAS_FADUMP_SKIP_TO_NEXT_CPU(reg_entry);
 			continue;
 		}