This is a note to let you know that I've just added the patch titled
KVM: PPC: Book3S HV: Don't try to signal cpu -1
to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-ppc-book3s-hv-don-t-try-to-signal-cpu-1.patch
and it can be found in the queue-4.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3deda5e50c893be38c1b6b3a73f8f8fb5560baa4 Mon Sep 17 00:00:00 2001
From: Paul Mackerras <paulus@xxxxxxxxxx>
Date: Tue, 20 Dec 2016 14:02:29 +1100
Subject: KVM: PPC: Book3S HV: Don't try to signal cpu -1
From: Paul Mackerras <paulus@xxxxxxxxxx>
commit 3deda5e50c893be38c1b6b3a73f8f8fb5560baa4 upstream.
If the target vcpu for kvmppc_fast_vcpu_kick_hv() is not running on
any CPU, then we will have vcpu->arch.thread_cpu == -1, and as it
happens, kvmppc_fast_vcpu_kick_hv will call kvmppc_ipi_thread with
-1 as the cpu argument. Although this is not meaningful, in the past,
before commit 1704a81ccebc ("KVM: PPC: Book3S HV: Use msgsnd for IPIs
to other cores on POWER9", 2016-11-18), it was harmless because CPU
-1 is not in the same core as any real CPU thread. On a POWER9,
however, we don't do the "same core" check, so we were trying to
do a msgsnd to thread -1, which is invalid. To avoid this, we add
a check to see that vcpu->arch.thread_cpu is >= 0 before calling
kvmppc_ipi_thread() with it. Since vcpu->arch.thread_vcpu can change
asynchronously, we use READ_ONCE to ensure that the value we check is
the same value that we use as the argument to kvmppc_ipi_thread().
Fixes: 1704a81ccebc ("KVM: PPC: Book3S HV: Use msgsnd for IPIs to other cores on POWER9")
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kvm/book3s_hv.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -182,7 +182,8 @@ static void kvmppc_fast_vcpu_kick_hv(str
++vcpu->stat.halt_wakeup;
}
- if (kvmppc_ipi_thread(vcpu->arch.thread_cpu))
+ cpu = READ_ONCE(vcpu->arch.thread_cpu);
+ if (cpu >= 0 && kvmppc_ipi_thread(cpu))
return;
/* CPU points to the first thread of the core */
Patches currently in stable-queue which might be from paulus@xxxxxxxxxx are
queue-4.10/powerpc-mm-fixup-wrong-lpcr_vrmasd-value.patch
queue-4.10/kvm-ppc-book3s-hv-don-t-try-to-signal-cpu-1.patch