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Re: [PATCH] xen/arm: smmuv1: Fixed stream matching register allocation





On 30/06/2021 18:49, Rahul Singh wrote:
Hi Julien,

Hi,

On 30 Jun 2021, at 10:09 am, Julien Grall <julien@xxxxxxx> wrote:

Hi Rahul,

On 25/06/2021 17:37, Rahul Singh wrote:
SMR allocation should be based on the number of supported stream
matching register for each SMMU device.
Issue introduced by commit 5e08586afbb90b2e2d56c175c07db77a4afa873c
when backported the patches from Linux to XEN to fix the stream match
conflict issue when two devices have the same stream-id.
Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Tested-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---
  xen/drivers/passthrough/arm/smmu.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/xen/drivers/passthrough/arm/smmu.c 
b/xen/drivers/passthrough/arm/smmu.c
index d9a3a0cbf6..da2cd457d7 100644
--- a/xen/drivers/passthrough/arm/smmu.c
+++ b/xen/drivers/passthrough/arm/smmu.c
@@ -149,6 +149,7 @@ typedef enum irqreturn irqreturn_t;
  #define kzalloc(size, flags)          _xzalloc(size, sizeof(void *))
  #define devm_kzalloc(dev, size, flags)        _xzalloc(size, sizeof(void *))
  #define kmalloc_array(size, n, flags) _xmalloc_array(size, sizeof(void *), n)
+#define kzalloc_array(size, n, flags)  _xzalloc_array(size, sizeof(void *), n)
    static void __iomem *devm_ioremap_resource(struct device *dev,
                                           struct resource *res)
@@ -2221,7 +2222,7 @@ static int arm_smmu_device_cfg_probe(struct 
arm_smmu_device *smmu)
                smmu->smr_mask_mask = smr >> SMR_MASK_SHIFT;
                /* Zero-initialised to mark as invalid */
-               smmu->smrs = devm_kzalloc(smmu->dev, sizeof(*smmu->smrs), 
GFP_KERNEL);
+               smmu->smrs = kzalloc_array(sizeof(*smmu->smrs), size, 
GFP_KERNEL);

I noticed this is already in... However, I am a bit puzzled into why this was 
switched devm_kzalloc() to kzalloc_array(). This doesn't matter for Xen as they 
are just wrappers to x*alloc() but a mention in the commit message would have 
been useful.

Yes we can use the devm_kzalloc(..) but then we have to pass 
(sizeof(*smmu->smrs) * size ) as size argument to devm_kzalloc(..)
I thought for better code readability I will use kzalloc_array() as the 
function name suggests we are allocating memory for an array.

My point is devm_k*alloc() and k*alloc() are quite different on the paper. One will allocate memory for a given device while the other is unknown memory.

It would have been better to call the function devm_kzalloc_array() to keep to keep the code coherent. Can you please send a patch to make the switch?

Cheers,

--
Julien Grall



 


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