Merge tag 'powerpc-4.13-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fixes from Michael Ellerman:
 "The highlight is Ben's patch to work around a host killing bug when
  running KVM guests with the Radix MMU on Power9. See the long change
  log of that commit for more detail.

  And then three fairly minor fixes:

   - fix of_node_put() underflow during reconfig remove, using old DLPAR
     tools.

   - fix recently introduced ld version check with 64-bit LE-only
     toolchain.

   - free the subpage_prot_table correctly, avoiding a memory leak.

  Thanks to: Aneesh Kumar K.V, Benjamin Herrenschmidt, Laurent Vivier"

* tag 'powerpc-4.13-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/mm/hash: Free the subpage_prot_table correctly
  powerpc/Makefile: Fix ld version check with 64-bit LE-only toolchain
  powerpc/pseries: Fix of_node_put() underflow during reconfig remove
  powerpc/mm/radix: Workaround prefetch issue with KVM

1 files changed, 43 insertions, 2 deletions

diff --git a/arch/powerpc/mm/tlb-radix.c b/arch/powerpc/mm/tlb-radix.c
index 744e0164ecf5..16ae1bbe13f0 100644
--- a/arch/powerpc/mm/tlb-radix.c
+++ b/arch/powerpc/mm/tlb-radix.c
@@ -12,12 +12,12 @@
 #include <linux/mm.h>
 #include <linux/hugetlb.h>
 #include <linux/memblock.h>
-#include <asm/ppc-opcode.h>
 
+#include <asm/ppc-opcode.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/trace.h>
-
+#include <asm/cputhreads.h>
 
 #define RIC_FLUSH_TLB 0
 #define RIC_FLUSH_PWC 1
@@ -454,3 +454,44 @@ void radix__flush_tlb_pte_p9_dd1(unsigned long old_pte, struct mm_struct *mm,
 	else
 		radix__flush_tlb_page_psize(mm, address, mmu_virtual_psize);
 }
+
+#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
+extern void radix_kvm_prefetch_workaround(struct mm_struct *mm)
+{
+	unsigned int pid = mm->context.id;
+
+	if (unlikely(pid == MMU_NO_CONTEXT))
+		return;
+
+	/*
+	 * If this context hasn't run on that CPU before and KVM is
+	 * around, there's a slim chance that the guest on another
+	 * CPU just brought in obsolete translation into the TLB of
+	 * this CPU due to a bad prefetch using the guest PID on
+	 * the way into the hypervisor.
+	 *
+	 * We work around this here. If KVM is possible, we check if
+	 * any sibling thread is in KVM. If it is, the window may exist
+	 * and thus we flush that PID from the core.
+	 *
+	 * A potential future improvement would be to mark which PIDs
+	 * have never been used on the system and avoid it if the PID
+	 * is new and the process has no other cpumask bit set.
+	 */
+	if (cpu_has_feature(CPU_FTR_HVMODE) && radix_enabled()) {
+		int cpu = smp_processor_id();
+		int sib = cpu_first_thread_sibling(cpu);
+		bool flush = false;
+
+		for (; sib <= cpu_last_thread_sibling(cpu) && !flush; sib++) {
+			if (sib == cpu)
+				continue;
+			if (paca[sib].kvm_hstate.kvm_vcpu)
+				flush = true;
+		}
+		if (flush)
+			_tlbiel_pid(pid, RIC_FLUSH_ALL);
+	}
+}
+EXPORT_SYMBOL_GPL(radix_kvm_prefetch_workaround);
+#endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */