linux-kernel - [PATCH kernel v12 19/34] powerpc/iommu: Fix IOMMU ownership control functions

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Date:	Fri,  5 Jun 2015 16:35:11 +1000
From:	Alexey Kardashevskiy <aik@...abs.ru>
To:	linuxppc-dev@...ts.ozlabs.org
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	Alex Williamson <alex.williamson@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	David Gibson <david@...son.dropbear.id.au>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH kernel v12 19/34] powerpc/iommu: Fix IOMMU ownership control functions

This adds missing locks in iommu_take_ownership()/
iommu_release_ownership().

This marks all pages busy in iommu_table::it_map in order to catch
errors if there is an attempt to use this table while ownership over it
is taken.

This only clears TCE content if there is no page marked busy in it_map.
Clearing must be done outside of the table locks as iommu_clear_tce()
called from iommu_clear_tces_and_put_pages() does this.

In order to use bitmap_empty(), the existing code clears bit#0 which
is set even in an empty table if it is bus-mapped at 0 as
iommu_init_table() reserves page#0 to prevent buggy drivers
from crashing when allocated page is bus-mapped at zero
(which is correct). This restores the bit in the case of failure
to bring the it_map to the state it was in when we called
iommu_take_ownership().

Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
Reviewed-by: David Gibson <david@...son.dropbear.id.au>
Reviewed-by: Gavin Shan <gwshan@...ux.vnet.ibm.com>
---
Changes:
v9:
* iommu_table_take_ownership() did not return @ret (and ignored EBUSY),
now it does return correct error.
* updated commit log about setting bit#0 in the case of failure

v5:
* do not store bit#0 value, it has to be set for zero-based table
anyway
* removed test_and_clear_bit
---
 arch/powerpc/kernel/iommu.c | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index e7f81b7..0fb8800 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -1035,31 +1035,51 @@ EXPORT_SYMBOL_GPL(iommu_tce_build);
 
 int iommu_take_ownership(struct iommu_table *tbl)
 {
-	unsigned long sz = (tbl->it_size + 7) >> 3;
+	unsigned long flags, i, sz = (tbl->it_size + 7) >> 3;
+	int ret = 0;
+
+	spin_lock_irqsave(&tbl->large_pool.lock, flags);
+	for (i = 0; i < tbl->nr_pools; i++)
+		spin_lock(&tbl->pools[i].lock);
 
 	if (tbl->it_offset == 0)
 		clear_bit(0, tbl->it_map);
 
 	if (!bitmap_empty(tbl->it_map, tbl->it_size)) {
 		pr_err("iommu_tce: it_map is not empty");
-		return -EBUSY;
+		ret = -EBUSY;
+		/* Restore bit#0 set by iommu_init_table() */
+		if (tbl->it_offset == 0)
+			set_bit(0, tbl->it_map);
+	} else {
+		memset(tbl->it_map, 0xff, sz);
 	}
 
-	memset(tbl->it_map, 0xff, sz);
+	for (i = 0; i < tbl->nr_pools; i++)
+		spin_unlock(&tbl->pools[i].lock);
+	spin_unlock_irqrestore(&tbl->large_pool.lock, flags);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(iommu_take_ownership);
 
 void iommu_release_ownership(struct iommu_table *tbl)
 {
-	unsigned long sz = (tbl->it_size + 7) >> 3;
+	unsigned long flags, i, sz = (tbl->it_size + 7) >> 3;
+
+	spin_lock_irqsave(&tbl->large_pool.lock, flags);
+	for (i = 0; i < tbl->nr_pools; i++)
+		spin_lock(&tbl->pools[i].lock);
 
 	memset(tbl->it_map, 0, sz);
 
 	/* Restore bit#0 set by iommu_init_table() */
 	if (tbl->it_offset == 0)
 		set_bit(0, tbl->it_map);
+
+	for (i = 0; i < tbl->nr_pools; i++)
+		spin_unlock(&tbl->pools[i].lock);
+	spin_unlock_irqrestore(&tbl->large_pool.lock, flags);
 }
 EXPORT_SYMBOL_GPL(iommu_release_ownership);
 
-- 
2.4.0.rc3.8.gfb3e7d5

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