Patch "KVM: PPC: Book3S HV: Hold kvm->lock around call to kvmppc_update_lpcr" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

    KVM: PPC: Book3S HV: Hold kvm->lock around call to kvmppc_update_lpcr

to the 4.13-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-hold-kvm-lock-around-call-to-kvmppc_update_lpcr.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Paul Mackerras <[email protected]>
Date: Mon, 11 Sep 2017 16:05:30 +1000
Subject: KVM: PPC: Book3S HV: Hold kvm->lock around call to kvmppc_update_lpcr

From: Paul Mackerras <[email protected]>

commit cf5f6f3125241853462334b1bc696f3c3c492178 upstream.

Commit 468808bd35c4 ("KVM: PPC: Book3S HV: Set process table for HPT guests on POWER9", 2017-01-30) added a call to kvmppc_update_lpcr() which doesn't hold the kvm->lock mutex around the call, as required. This adds the lock/unlock pair, and for good measure, includes the kvmppc_setup_partition_table() call in the locked region, since it is altering global state of the VM.

This error appears not to have any fatal consequences for the host; the consequences would be that the VCPUs could end up running with different LPCR values, or an update to the LPCR value by userspace using the one_reg interface could get overwritten, or the update done by kvmhv_configure_mmu() could get overwritten.

---
 arch/powerpc/kvm/book3s_hv.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -4187,11 +4187,13 @@ static int kvmhv_configure_mmu(struct kv
 	if ((cfg->process_table & PRTS_MASK) > 24)
 		return -EINVAL;
 
+	mutex_lock(&kvm->lock);
 	kvm->arch.process_table = cfg->process_table;
 	kvmppc_setup_partition_table(kvm);
 
 	lpcr = (cfg->flags & KVM_PPC_MMUV3_GTSE) ? LPCR_GTSE : 0;
 	kvmppc_update_lpcr(kvm, lpcr, LPCR_GTSE);
+	mutex_unlock(&kvm->lock);
 
 	return 0;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/kvm-ppc-book3s-hv-hold-kvm-lock-around-call-to-kvmppc_update_lpcr.patch queue-4.13/kvm-ppc-book3s-hv-don-t-access-xive-pipr-register-using-byte-accesses.patch queue-4.13/kvm-ppc-book3s-hv-fix-bug-causing-host-slb-to-be-restored-incorrectly.patch