linux-kernel - Re: [PATCH v3] s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated

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Date:   Mon, 14 Dec 2020 14:39:17 -0500
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, stable@...r.kernel.org, sashal@...nel.org,
        borntraeger@...ibm.com, cohuck@...hat.com, kwankhede@...dia.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pasic@...ux.vnet.ibm.com
Subject: Re: [PATCH v3] s390/vfio-ap: clean up vfio_ap resources when KVM
 pointer invalidated



On 12/14/20 12:07 PM, Greg KH wrote:
> On Mon, Dec 14, 2020 at 11:56:17AM -0500, Tony Krowiak wrote:
>> The vfio_ap device driver registers a group notifier with VFIO when the
>> file descriptor for a VFIO mediated device for a KVM guest is opened to
>> receive notification that the KVM pointer is set (VFIO_GROUP_NOTIFY_SET_KVM
>> event). When the KVM pointer is set, the vfio_ap driver takes the
>> following actions:
>> 1. Stashes the KVM pointer in the vfio_ap_mdev struct that holds the state
>>     of the mediated device.
>> 2. Calls the kvm_get_kvm() function to increment its reference counter.
>> 3. Sets the function pointer to the function that handles interception of
>>     the instruction that enables/disables interrupt processing.
>> 4. Sets the masks in the KVM guest's CRYCB to pass AP resources through to
>>     the guest.
>>
>> In order to avoid memory leaks, when the notifier is called to receive
>> notification that the KVM pointer has been set to NULL, the vfio_ap device
>> driver should reverse the actions taken when the KVM pointer was set.
>>
>> Fixes: 258287c994de ("s390: vfio-ap: implement mediated device open callback")
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.ibm.com>
>> ---
>>   drivers/s390/crypto/vfio_ap_ops.c | 29 ++++++++++++++++++++---------
>>   1 file changed, 20 insertions(+), 9 deletions(-)
> <formletter>
>
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree.  Please read:
>      https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> for how to do this properly.
>
> </formletter>

I read the document on the correct way to submit patches for inclusion in
the stable kernel. I apologize for my ignorance, but I don't see the
problem. Can you help me out here? Does a patch that fixes a memory leak
not qualify or is it something else?