linux-kernel - [PATCH AUTOSEL 4.19 192/671] KVM: PPC: Release all hardware TCE tables attached to a group

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Date:   Thu, 16 Jan 2020 11:51:41 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Alexey Kardashevskiy <aik@...abs.ru>,
        Paul Mackerras <paulus@...abs.org>,
        Sasha Levin <sashal@...nel.org>, kvm-ppc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH AUTOSEL 4.19 192/671] KVM: PPC: Release all hardware TCE tables attached to a group

From: Alexey Kardashevskiy <aik@...abs.ru>

[ Upstream commit a67614cc05a5052b265ea48196dab2fce11f5f2e ]

The SPAPR TCE KVM device references all hardware IOMMU tables assigned to
some IOMMU group to ensure that in-kernel KVM acceleration of H_PUT_TCE
can work. The tables are references when an IOMMU group gets registered
with the VFIO KVM device by the KVM_DEV_VFIO_GROUP_ADD ioctl;
KVM_DEV_VFIO_GROUP_DEL calls into the dereferencing code
in kvm_spapr_tce_release_iommu_group() which walks through the list of
LIOBNs, finds a matching IOMMU table and calls kref_put() when found.

However that code stops after the very first successful derefencing
leaving other tables referenced till the SPAPR TCE KVM device is destroyed
which normally happens on guest reboot or termination so if we do hotplug
and unplug in a loop, we are leaking IOMMU tables here.

This removes a premature return to let kvm_spapr_tce_release_iommu_group()
find and dereference all attached tables.

Fixes: 121f80ba68f ("KVM: PPC: VFIO: Add in-kernel acceleration for VFIO")
Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
Signed-off-by: Paul Mackerras <paulus@...abs.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/kvm/book3s_64_vio.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index 65486c3d029b..26b03af71abd 100644
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -133,7 +133,6 @@ extern void kvm_spapr_tce_release_iommu_group(struct kvm *kvm,
 					continue;

 				kref_put(&stit->kref, kvm_spapr_tce_liobn_put);
-				return;
 			}
 		}
 	}
-- 
2.20.1