From: Tony Krowiak <akrowiak@linux.ibm.com>
To: pmorel@linux.ibm.com, borntraeger@de.ibm.com
Cc: alex.williamson@redhat.com, cohuck@redhat.com,
linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
kvm@vger.kernel.org, frankja@linux.ibm.com, pasic@linux.ibm.com,
david@redhat.com, schwidefsky@de.ibm.com,
heiko.carstens@de.ibm.com, freude@linux.ibm.com,
mimu@linux.ibm.com
Subject: Re: [PATCH v6 4/7] vfio: ap: register IOMMU VFIO notifier
Date: Fri, 29 Mar 2019 09:14:48 -0400 [thread overview]
Message-ID: <9af30e31-e4d8-160e-d7a1-8365185d2933@linux.ibm.com> (raw)
In-Reply-To: <7a4bf9f1-5046-5838-a50d-8402782c880f@linux.ibm.com>
On 3/29/19 5:31 AM, Pierre Morel wrote:
> On 28/03/2019 21:46, Tony Krowiak wrote:
>> On 3/22/19 10:43 AM, Pierre Morel wrote:
>>> To be able to use the VFIO interface to facilitate the
>>> mediated device memory pinning/unpinning we need to register
>>> a notifier for IOMMU.
>>>
>>> While we will start to pin one guest page for the interrupt indicator
>>> byte, this is still ok with ballooning as this page will never be
>>> used by the guest virtio-balloon driver.
>>> So the pinned page will never be freed. And even a broken guest does
>>> so, that would not impact the host as the original page is still
>>> in control by vfio.
>>
>> I apologize, but I do not understand what you are saying in the second
>> sentence of the paragraph above. Why will the pinned page never be freed?
> Because it is in use by the guest's kernel as a notification information
> byte for the original PQAP AQIC.
Your comment says the pinned page will never be free, doesn't it get
freed when the guest is terminated?
>
> I understand that the pinned page is under the control of vfio
>> until it is freed, but have no idea what you mean by "and even a broken
>> guest does so"? A broken guest does what? Can you please reword this so
>> it makes more sense?
>
> A broken guest could free the page used for the NIB. What is obviously
> wrong.
Then why not simply say a pinned page is under the control of the
vfio driver, so if a broken (malicious?) guest frees the page, it will
not impact the host or something to that effect.
>
>>
>>>
>>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>>> ---
>>> drivers/s390/crypto/vfio_ap_ops.c | 38
>>> +++++++++++++++++++++++++++++++++++
>>> drivers/s390/crypto/vfio_ap_private.h | 2 ++
>>> 2 files changed, 40 insertions(+)
>>>
>>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c
>>> b/drivers/s390/crypto/vfio_ap_ops.c
>>> index bdb36e0..3478499 100644
>>> --- a/drivers/s390/crypto/vfio_ap_ops.c
>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c
>>> @@ -787,6 +787,35 @@ static const struct attribute_group
>>> *vfio_ap_mdev_attr_groups[] = {
>>> NULL
>>> };
>>> +/**
>>> + * vfio_ap_mdev_iommu_notifier: IOMMU notifier callback
>>> + *
>>> + * @nb: The notifier block
>>> + * @action: Action to be taken
>>> + * @data: data associated with the request
>>> + *
>>> + * For an UNMAP request, unpin the guest IOVA (the NIB guest address we
>>> + * pinned before). Other requests are ignored.
>>> + *
>>> + */
>>> +static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
>>> + unsigned long action, void *data)
>>> +{
>>> + struct ap_matrix_mdev *matrix_mdev;
>>> +
>>> + matrix_mdev = container_of(nb, struct ap_matrix_mdev,
>>> iommu_notifier);
>>> +
>>
>> I don't understand why we registered this notifier. I may be wrong, but
>> AFAIU, this notifier will be invoked only when the VFIO_IOMMU_UNMAP_DMA
>> ioctl is called from userspace. I did an experiment and inserted some
>> printf's to see if this ever gets called and verified it does not. Maybe
>> you have a good reason of which I'm not aware. Can you enlighten me
>> here?
>
> The vfio_iommu_type1 pin page requires a notifier.
>
> Regards,
> Pierre
>
next prev parent reply other threads:[~2019-03-29 13:14 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-22 14:43 [PATCH v6 0/7] vfio: ap: AP Queue Interrupt Control Pierre Morel
2019-03-22 14:43 ` [PATCH v6 1/7] s390: ap: kvm: add PQAP interception for AQIC Pierre Morel
2019-03-26 18:57 ` Tony Krowiak
2019-03-27 16:06 ` Tony Krowiak
2019-03-28 12:43 ` Pierre Morel
2019-03-28 15:24 ` Tony Krowiak
2019-03-28 16:12 ` Tony Krowiak
2019-03-29 8:52 ` Pierre Morel
2019-03-29 13:02 ` Tony Krowiak
2019-03-22 14:43 ` [PATCH v6 2/7] s390: ap: new vfio_ap_queue structure Pierre Morel
2019-03-25 8:05 ` Harald Freudenberger
2019-03-28 13:12 ` Pierre Morel
2019-03-26 20:45 ` Tony Krowiak
2019-03-27 11:00 ` Harald Freudenberger
2019-03-28 12:53 ` Pierre Morel
2019-03-28 13:06 ` Pierre Morel
2019-03-28 15:32 ` Tony Krowiak
2019-03-28 16:06 ` Pierre Morel
2019-04-02 12:47 ` Pierre Morel
2019-03-22 14:43 ` [PATCH v6 3/7] s390: ap: setup relation betwen KVM and mediated device Pierre Morel
2019-03-28 16:12 ` Tony Krowiak
2019-03-28 16:27 ` Pierre Morel
2019-03-28 17:25 ` Tony Krowiak
2019-03-29 8:58 ` Pierre Morel
2019-03-29 13:06 ` Tony Krowiak
2019-03-22 14:43 ` [PATCH v6 4/7] vfio: ap: register IOMMU VFIO notifier Pierre Morel
2019-03-28 20:46 ` Tony Krowiak
2019-03-29 9:31 ` Pierre Morel
2019-03-29 13:14 ` Tony Krowiak [this message]
2019-03-22 14:43 ` [PATCH v6 5/7] s390: ap: implement PAPQ AQIC interception in kernel Pierre Morel
2019-03-22 14:43 ` [PATCH v6 6/7] s390: ap: Cleanup on removing the AP device Pierre Morel
2019-03-22 14:43 ` [PATCH v6 7/7] s390: ap: kvm: Enable PQAP/AQIC facility for the guest Pierre Morel
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