linux-kernel - [PATCH 4.4 68/76] vfio/spapr: Postpone allocation of userspace version of TCE table

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Date:   Tue, 28 Mar 2017 14:31:05 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        David Gibson <david@...son.dropbear.id.au>,
        Alex Williamson <alex.williamson@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <alexander.levin@...izon.com>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: [PATCH 4.4 68/76] vfio/spapr: Postpone allocation of userspace version of TCE table

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sumit Semwal <sumit.semwal@...aro.org>


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

[ Upstream commit 39701e56f5f16ea0cf8fc9e8472e645f8de91d23 ]

The iommu_table struct manages a hardware TCE table and a vmalloc'd
table with corresponding userspace addresses. Both are allocated when
the default DMA window is created and this happens when the very first
group is attached to a container.

As we are going to allow the userspace to configure container in one
memory context and pas container fd to another, we have to postpones
such allocations till a container fd is passed to the destination
user process so we would account locked memory limit against the actual
container user constrainsts.

This postpones the it_userspace array allocation till it is used first
time for mapping. The unmapping patch already checks if the array is
allocated.

Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
Reviewed-by: David Gibson <david@...son.dropbear.id.au>
Acked-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sumit Semwal <sumit.semwal@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/vfio/vfio_iommu_spapr_tce.c |   20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -511,6 +511,12 @@ static long tce_iommu_build_v2(struct tc
 	unsigned long hpa;
 	enum dma_data_direction dirtmp;
 
+	if (!tbl->it_userspace) {
+		ret = tce_iommu_userspace_view_alloc(tbl);
+		if (ret)
+			return ret;
+	}
+
 	for (i = 0; i < pages; ++i) {
 		struct mm_iommu_table_group_mem_t *mem = NULL;
 		unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl,
@@ -584,15 +590,6 @@ static long tce_iommu_create_table(struc
 	WARN_ON(!ret && !(*ptbl)->it_ops->free);
 	WARN_ON(!ret && ((*ptbl)->it_allocated_size != table_size));
 
-	if (!ret && container->v2) {
-		ret = tce_iommu_userspace_view_alloc(*ptbl);
-		if (ret)
-			(*ptbl)->it_ops->free(*ptbl);
-	}
-
-	if (ret)
-		decrement_locked_vm(table_size >> PAGE_SHIFT);
-
 	return ret;
 }
 
@@ -1064,10 +1061,7 @@ static int tce_iommu_take_ownership(stru
 		if (!tbl || !tbl->it_map)
 			continue;
 
-		rc = tce_iommu_userspace_view_alloc(tbl);
-		if (!rc)
-			rc = iommu_take_ownership(tbl);
-
+		rc = iommu_take_ownership(tbl);
 		if (rc) {
 			for (j = 0; j < i; ++j)
 				iommu_release_ownership(