Re: [PATCH kernel v10 05/34] powerpc/iommu: Always release iommu_table in iommu_free_table()

From: Alexey Kardashevskiy
Date: Wed May 13 2015 - 22:34:46 EST

On 05/14/2015 09:27 AM, Gavin Shan wrote:
On Wed, May 13, 2015 at 02:51:36PM +0200, Thomas Huth wrote:
On Wed, 13 May 2015 16:30:16 +1000
Alexey Kardashevskiy <aik@xxxxxxxxx> wrote:

On 05/13/2015 03:33 PM, Gavin Shan wrote:
On Tue, May 12, 2015 at 01:38:54AM +1000, Alexey Kardashevskiy wrote:
At the moment iommu_free_table() only releases memory if
the table was initialized for the platform code use, i.e. it had
it_map initialized (which purpose is to track DMA memory space use).

With dynamic DMA windows, we will need to be able to release
iommu_table even if it was used for VFIO in which case it_map is NULL
so does the patch.

Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>

Reviewed-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>

arch/powerpc/kernel/iommu.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 3d47eb3..2c02d4c 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -714,8 +714,7 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name)
unsigned int order;

if (!tbl || !tbl->it_map) {
- printk(KERN_ERR "%s: expected TCE map for %s\n", __func__,
- node_name);
+ kfree(tbl);

I'm not sure if the "tbl" needs to be checked against NULL as kfree() already
has the check. But it looks a bit strange to free NULL "tbl" from the code

Yeah, looks a bit weird, agree, I'll change but in general kfree/vfree/...
- they all check the passed pointer for NULL.

But if tbl is NULL, the tbl->it_map check will fail, won't it? So in
this case, I think you have to keep it.

If I understood your question correctly, "tbl->it_map" won't be checked
when "tbl" is NULL because the connection ("||") for the two conditions.
The code can be changed to something like below if Alexey want:

if (!tbl)
if (!tbl->itmap)

To be precise ;)

if (!tbl->itmap) {


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