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KVM: PPC: Book3S: Protect kvmppc_gpa_to_ua() with SRCU

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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: 121f80ba68 ("KVM: PPC: VFIO: Add in-kernel acceleration for VFIO")
Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Alexey Kardashevskiy 2017-10-11 16:00:34 +11:00 committed by Paul Mackerras
parent 2cde371632
commit 8f6a9f0d06
1 changed files with 14 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
arch/powerpc/kvm/book3s_64_vio.c
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@ -478,28 +478,30 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
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);
@ -507,7 +509,10 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
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);