This is a note to let you know that I've just added the patch titled
KVM: PPC: Book3S: Protect kvmppc_gpa_to_ua() with SRCU
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-protect-kvmppc_gpa_to_ua-with-srcu.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 <stable@xxxxxxxxxxxxxxx> know about it.
>From 8f6a9f0d0604817f7c8d4376fd51718f1bf192ee Mon Sep 17 00:00:00 2001
From: Alexey Kardashevskiy <aik@xxxxxxxxx>
Date: Wed, 11 Oct 2017 16:00:34 +1100
Subject: KVM: PPC: Book3S: Protect kvmppc_gpa_to_ua() with SRCU
From: Alexey Kardashevskiy <aik@xxxxxxxxx>
commit 8f6a9f0d0604817f7c8d4376fd51718f1bf192ee upstream.
kvmppc_gpa_to_ua() accesses KVM memory slot array via
srcu_dereference_check() and this produces warnings from RCU like below.
This extends the existing srcu_read_lock/unlock to cover that
kvmppc_gpa_to_ua() as well.
We did not hit this before as this lock is not needed for the realmode
handlers and hash guests would use the realmode path all the time;
however the radix guests are always redirected to the virtual mode
handlers and hence the warning.
[ 68.253798] ./include/linux/kvm_host.h:575 suspicious rcu_dereference_check() usage!
[ 68.253799]
other info that might help us debug this:
[ 68.253802]
rcu_scheduler_active = 2, debug_locks = 1
[ 68.253804] 1 lock held by qemu-system-ppc/6413:
[ 68.253806] #0: (&vcpu->mutex){+.+.}, at: [<c00800000e3c22f4>] vcpu_load+0x3c/0xc0 [kvm]
[ 68.253826]
stack backtrace:
[ 68.253830] CPU: 92 PID: 6413 Comm: qemu-system-ppc Tainted: G W 4.14.0-rc3-00553-g432dcba58e9c-dirty #72
[ 68.253833] Call Trace:
[ 68.253839] [c000000fd3d9f790] [c000000000b7fcc8] dump_stack+0xe8/0x160 (unreliable)
[ 68.253845] [c000000fd3d9f7d0] [c0000000001924c0] lockdep_rcu_suspicious+0x110/0x180
[ 68.253851] [c000000fd3d9f850] [c0000000000e825c] kvmppc_gpa_to_ua+0x26c/0x2b0
[ 68.253858] [c000000fd3d9f8b0] [c00800000e3e1984] kvmppc_h_put_tce+0x12c/0x2a0 [kvm]
Fixes: 121f80ba68f1 ("KVM: PPC: VFIO: Add in-kernel acceleration for VFIO")
Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kvm/book3s_64_vio.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -479,28 +479,30 @@ long kvmppc_h_put_tce(struct kvm_vcpu *v
return ret;
dir = iommu_tce_direction(tce);
+
+ idx = srcu_read_lock(&vcpu->kvm->srcu);
+
if ((dir != DMA_NONE) && kvmppc_gpa_to_ua(vcpu->kvm,
- tce & ~(TCE_PCI_READ | TCE_PCI_WRITE), &ua, NULL))
- return H_PARAMETER;
+ tce & ~(TCE_PCI_READ | TCE_PCI_WRITE), &ua, NULL)) {
+ ret = H_PARAMETER;
+ goto unlock_exit;
+ }
entry = ioba >> stt->page_shift;
list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
- if (dir == DMA_NONE) {
+ if (dir == DMA_NONE)
ret = kvmppc_tce_iommu_unmap(vcpu->kvm,
stit->tbl, entry);
- } else {
- idx = srcu_read_lock(&vcpu->kvm->srcu);
+ else
ret = kvmppc_tce_iommu_map(vcpu->kvm, stit->tbl,
entry, ua, dir);
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
- }
if (ret == H_SUCCESS)
continue;
if (ret == H_TOO_HARD)
- return ret;
+ goto unlock_exit;
WARN_ON_ONCE(1);
kvmppc_clear_tce(stit->tbl, entry);
@@ -508,7 +510,10 @@ long kvmppc_h_put_tce(struct kvm_vcpu *v
kvmppc_tce_put(stt, entry, tce);
- return H_SUCCESS;
+unlock_exit:
+ srcu_read_unlock(&vcpu->kvm->srcu, idx);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(kvmppc_h_put_tce);
Patches currently in stable-queue which might be from aik@xxxxxxxxx are
queue-4.13/kvm-ppc-book3s-protect-kvmppc_gpa_to_ua-with-srcu.patch