From: Nicholas Piggin <npiggin@gmail.com>
Date: Tue, 12 Jun 2018 09:38:08 +0000 (+1000)
Subject: powerpc/64s/radix: Fix radix_kvm_prefetch_workaround paca access of not possible CPU
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=758380b8155f69b4e2f77f27562f8a7a466749d6;p=openwrt%2Fstaging%2Fblogic.git

powerpc/64s/radix: Fix radix_kvm_prefetch_workaround paca access of not possible CPU

If possible CPUs are limited (e.g., by kexec), then the kvm prefetch
workaround function can access the paca pointer for a !possible CPU.

Fixes: d2e60075a3d44 ("powerpc/64: Use array of paca pointers and allocate pacas individually")
Cc: stable@kernel.org
Reported-by: Pridhiviraj Paidipeddi <ppaidipe@linux.vnet.ibm.com>
Tested-by: Pridhiviraj Paidipeddi <ppaidipe@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---

diff --git a/arch/powerpc/mm/tlb-radix.c b/arch/powerpc/mm/tlb-radix.c
index a734e486664d..1135b43a597c 100644
--- a/arch/powerpc/mm/tlb-radix.c
+++ b/arch/powerpc/mm/tlb-radix.c
@@ -1097,6 +1097,8 @@ extern void radix_kvm_prefetch_workaround(struct mm_struct *mm)
 		for (; sib <= cpu_last_thread_sibling(cpu) && !flush; sib++) {
 			if (sib == cpu)
 				continue;
+			if (!cpu_possible(sib))
+				continue;
 			if (paca_ptrs[sib]->kvm_hstate.kvm_vcpu)
 				flush = true;
 		}