Merge tag 'powerpc-4.11-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc updates from Michael Ellerman:
 "Highlights include:

   - Support for direct mapped LPC on POWER9, giving Linux direct access
     to devices that may be on there such as a UART.

   - Memory hotplug support for the Power9 Radix MMU.

   - Add new AUX vectors describing the processor's cache geometry, to
     be used by glibc.

   - The ability for a guest to ask the hypervisor to resize the guest's
     hash table, and in addition support for doing so automatically when
     memory is hotplugged into/out-of the guest. This allows the hash
     table to be sized based on the current memory usage of the guest,
     rather than the maximum possible memory usage.

   - Implementation of optprobes (kprobe optimisation) for powerpc.

  In addition there's the topic branch shared with the KVM tree, which
  includes support for guests to use the Radix MMU on Power9.

  Thanks to:
    Alistair Popple, Andrew Donnellan, Aneesh Kumar K.V, Anju T, Anton
    Blanchard, Benjamin Herrenschmidt, Chris Packham, Daniel Axtens,
    Daniel Borkmann, David Gibson, Finn Thain, Gautham R. Shenoy, Gavin
    Shan, Greg Kurz, Joel Stanley, John Allen, Madhavan Srinivasan,
    Mahesh Salgaonkar, Markus Elfring, Michael Neuling, Nathan Fontenot,
    Naveen N. Rao, Nicholas Piggin, Paul Mackerras, Ravi Bangoria, Reza
    Arbab, Shailendra Singh, Vaibhav Jain, Wei Yongjun"

* tag 'powerpc-4.11-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (129 commits)
  powerpc/mm/radix: Skip ptesync in pte update helpers
  powerpc/mm/radix: Use ptep_get_and_clear_full when clearing pte for full mm
  powerpc/mm/radix: Update pte update sequence for pte clear case
  powerpc/mm: Update PROTFAULT handling in the page fault path
  powerpc/xmon: Fix data-breakpoint
  powerpc/mm: Fix build break with BOOK3S_64=n and MEMORY_HOTPLUG=y
  powerpc/mm: Fix build break when CMA=n && SPAPR_TCE_IOMMU=y
  powerpc/mm: Fix build break with RADIX=y & HUGETLBFS=n
  powerpc/pseries: Fix typo in parameter description
  powerpc/kprobes: Remove kprobe_exceptions_notify()
  kprobes: Introduce weak variant of kprobe_exceptions_notify()
  powerpc/ftrace: Fix confusing help text for DISABLE_MPROFILE_KERNEL
  powerpc/powernv: Fix opal_exit tracepoint opcode
  powerpc: Add a prototype for mcount() so it can be versioned
  powerpc: Drop GPL from of_node_to_nid() export to match other arches
  powerpc/kprobes: Optimize kprobe in kretprobe_trampoline()
  powerpc/kprobes: Implement Optprobes
  powerpc/kprobes: Fixes for kprobe_lookup_name() on BE
  powerpc: Add helper to check if offset is within relative branch range
  powerpc/bpf: Introduce __PPC_SH64()
  ...

1 files changed, 24 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 8f0c7c5d93f2..8ff0dd4e77a7 100644
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -406,12 +406,35 @@ static void register_fw_dump(struct fadump_mem_struct *fdm)
 void crash_fadump(struct pt_regs *regs, const char *str)
 {
 	struct fadump_crash_info_header *fdh = NULL;
+	int old_cpu, this_cpu;
 
 	if (!fw_dump.dump_registered || !fw_dump.fadumphdr_addr)
 		return;
 
+	/*
+	 * old_cpu == -1 means this is the first CPU which has come here,
+	 * go ahead and trigger fadump.
+	 *
+	 * old_cpu != -1 means some other CPU has already on it's way
+	 * to trigger fadump, just keep looping here.
+	 */
+	this_cpu = smp_processor_id();
+	old_cpu = cmpxchg(&crashing_cpu, -1, this_cpu);
+
+	if (old_cpu != -1) {
+		/*
+		 * We can't loop here indefinitely. Wait as long as fadump
+		 * is in force. If we race with fadump un-registration this
+		 * loop will break and then we go down to normal panic path
+		 * and reboot. If fadump is in force the first crashing
+		 * cpu will definitely trigger fadump.
+		 */
+		while (fw_dump.dump_registered)
+			cpu_relax();
+		return;
+	}
+
 	fdh = __va(fw_dump.fadumphdr_addr);
-	crashing_cpu = smp_processor_id();
 	fdh->crashing_cpu = crashing_cpu;
 	crash_save_vmcoreinfo();