linux-kernel - Re: [PATCH V1] accel/amdxdna: Hold mm structure across iommu_sva_unbind

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Message-ID: <61d54b62-9582-a945-be83-57e651c8691d@amd.com>
Date: Fri, 30 Jan 2026 13:10:31 -0800
From: Lizhi Hou <lizhi.hou@....com>
To: Mario Limonciello <mario.limonciello@....com>, <ogabbay@...nel.org>,
	<quic_jhugo@...cinc.com>, <dri-devel@...ts.freedesktop.org>,
	<maciej.falkowski@...ux.intel.com>
CC: <linux-kernel@...r.kernel.org>, <max.zhen@....com>, <sonal.santan@....com>
Subject: Re: [PATCH V1] accel/amdxdna: Hold mm structure across
 iommu_sva_unbind_device()

Applied to drm-misc-next-fixes

On 1/30/26 11:39, Mario Limonciello wrote:
> On 1/27/26 6:23 PM, Lizhi Hou wrote:
>> Some tests trigger a crash in iommu_sva_unbind_device() due to
>> accessing iommu_mm after the associated mm structure has been
>> freed.
>>
>> Fix this by taking an explicit reference to the mm structure
>> after successfully binding the device, and releasing it only
>> after the device is unbound. This ensures the mm remains valid
>> for the entire SVA bind/unbind lifetime.
>>
>> Fixes: be462c97b7df ("accel/amdxdna: Add hardware context")
>> Signed-off-by: Lizhi Hou <lizhi.hou@....com>
> Reviewed-by: Mario Limonciello (AMD) <superm1@...nel.org>
>> ---
>>   drivers/accel/amdxdna/amdxdna_pci_drv.c | 3 +++
>>   drivers/accel/amdxdna/amdxdna_pci_drv.h | 1 +
>>   2 files changed, 4 insertions(+)
>>
>> diff --git a/drivers/accel/amdxdna/amdxdna_pci_drv.c 
>> b/drivers/accel/amdxdna/amdxdna_pci_drv.c
>> index 45f5c12fc67f..fdefd9ec2066 100644
>> --- a/drivers/accel/amdxdna/amdxdna_pci_drv.c
>> +++ b/drivers/accel/amdxdna/amdxdna_pci_drv.c
>> @@ -82,6 +82,8 @@ static int amdxdna_drm_open(struct drm_device 
>> *ddev, struct drm_file *filp)
>>           ret = -ENODEV;
>>           goto unbind_sva;
>>       }
>> +    client->mm = current->mm;
>> +    mmgrab(client->mm);
>>       init_srcu_struct(&client->hwctx_srcu);
>>       xa_init_flags(&client->hwctx_xa, XA_FLAGS_ALLOC);
>>       mutex_init(&client->mm_lock);
>> @@ -116,6 +118,7 @@ static void amdxdna_client_cleanup(struct 
>> amdxdna_client *client)
>>           drm_gem_object_put(to_gobj(client->dev_heap));
>>         iommu_sva_unbind_device(client->sva);
>> +    mmdrop(client->mm);
>>         kfree(client);
>>   }
>> diff --git a/drivers/accel/amdxdna/amdxdna_pci_drv.h 
>> b/drivers/accel/amdxdna/amdxdna_pci_drv.h
>> index 6580cb5ec7e2..f08406b8fdf9 100644
>> --- a/drivers/accel/amdxdna/amdxdna_pci_drv.h
>> +++ b/drivers/accel/amdxdna/amdxdna_pci_drv.h
>> @@ -130,6 +130,7 @@ struct amdxdna_client {
>>         struct iommu_sva        *sva;
>>       int                pasid;
>> +    struct mm_struct        *mm;
>>   };
>>     #define amdxdna_for_each_hwctx(client, hwctx_id, entry)        \
>