From: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
To: Halil Pasic <pasic@linux.ibm.com>,
linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org
Cc: freude@de.ibm.com, schwidefsky@de.ibm.com,
heiko.carstens@de.ibm.com, borntraeger@de.ibm.com,
cohuck@redhat.com, kwankhede@nvidia.com,
bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com,
alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com,
alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com,
jjherne@linux.vnet.ibm.com, thuth@redhat.com,
pasic@linux.vnet.ibm.com, berrange@redhat.com,
fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com
Subject: Re: [PATCH v5 06/13] KVM: s390: interfaces to manage guest's AP matrix
Date: Wed, 16 May 2018 10:29:10 -0400 [thread overview]
Message-ID: <bf6191a9-ca0f-238c-d078-d6f0d6be1616@linux.vnet.ibm.com> (raw)
In-Reply-To: <be2e8810-2a03-c67c-b1aa-41cf7c82980e@linux.ibm.com>
On 05/11/2018 12:08 PM, Halil Pasic wrote:
>
>
> On 05/07/2018 05:11 PM, Tony Krowiak wrote:
>> Provides interfaces to manage the AP adapters, usage domains
>> and control domains assigned to a KVM guest.
>>
>> The guest's SIE state description has a satellite structure called the
>> Crypto Control Block (CRYCB) containing three bitmask fields
>> identifying the adapters, queues (domains) and control domains
>> assigned to the KVM guest:
>
> [..]
>
>> index 00bcfb0..98b53c7 100644
>> --- a/arch/s390/kvm/kvm-ap.c
>> +++ b/arch/s390/kvm/kvm-ap.c
>> @@ -7,6 +7,7 @@
>
> [..]
>
>> +
>> +/**
>> + * kvm_ap_validate_queue_sharing
>> + *
>> + * Verifies that the APQNs derived from the cross product of the AP
>> adapter IDs
>> + * and AP queue indexes comprising the AP matrix are not configured for
>> + * another guest. AP queue sharing is not allowed.
>> + *
>> + * @kvm: the KVM guest
>> + * @matrix: the AP matrix
>> + *
>> + * Returns 0 if the APQNs are valid, otherwise; returns -EBUSY.
>> + */
>> +static int kvm_ap_validate_queue_sharing(struct kvm *kvm,
>> + struct kvm_ap_matrix *matrix)
>> +{
>> + struct kvm *vm;
>> + unsigned long *apm, *aqm;
>> + unsigned long apid, apqi;
>> +
>> +
>> + /* No other VM may share an AP Queue with the input VM */
>> + list_for_each_entry(vm, &vm_list, vm_list) {
>> + if (kvm == vm)
>> + continue;
>> +
>> + apm = kvm_ap_get_crycb_apm(vm);
>> + if (!bitmap_and(apm, apm, matrix->apm, matrix->apm_max + 1))
>> + continue;
>> +
>> + aqm = kvm_ap_get_crycb_aqm(vm);
>> + if (!bitmap_and(aqm, aqm, matrix->aqm, matrix->aqm_max + 1))
>> + continue;
>> +
>> + for_each_set_bit_inv(apid, apm, matrix->apm_max + 1)
>> + for_each_set_bit_inv(apqi, aqm, matrix->aqm_max + 1)
>> + kvm_ap_log_sharing_err(vm, apid, apqi);
>> +
>> + return -EBUSY;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +int kvm_ap_configure_matrix(struct kvm *kvm, struct kvm_ap_matrix
>> *matrix)
>> +{
>> + int ret = 0;
>> +
>> + mutex_lock(&kvm->lock);
>
> You seem to take only kvm->lock, vm_list however (used in
> kvm_ap_validate_queue_sharing()) seems to be protected by
> kvm_lock.
>
> Can you tell me why is this supposed to be safe?
>
> What is supposed to prevent an execution like
> vm1: call kvm_ap_configure_matrix(m1)
> vm2: call kvm_ap_configure_matrix(m2)
> vm1: call kvm_ap_validate_queue_sharing(m1)
> vm2: call kvm_ap_validate_queue_sharing(m2)
> vm1: call kvm_ap_set_crycb_masks(m1)
> vm2: call kvm_ap_set_crycb_masks(m2)
>
> where, let's say, m1 and m2 are equal in the sense that the
> mask values are the same?
vm1 will get the kvm->lock first in your scenario when
kvm_ap_configure_matrix(m1) is invoked. Since the other
functions - i.e., kvm_ap_validate_queue_sharing(m1) and
kvm_ap_set_crycb_masks(m1) - are static and only called
from the kvm_ap_configure_matrix(m1), your scenario
can never happen because vm2 will not get the lock until
kvm_ap_configure_matrix(m1) has completed. I see your
point, however, and maybe I should also acquire the kvm_lock.
>
>
> Regards,
> Halil
>
>> +
>> + ret = kvm_ap_validate_queue_sharing(kvm, matrix);
>> + if (ret)
>> + goto done;
>> +
>> + kvm_ap_set_crycb_masks(kvm, matrix);
>> +
>> +done:
>> + mutex_unlock(&kvm->lock);
>> +
>> + return ret;
>> +}
>> +EXPORT_SYMBOL(kvm_ap_configure_matrix);
>> +
next prev parent reply other threads:[~2018-05-16 14:29 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-07 15:11 [PATCH v5 00/13] s390: vfio-ap: guest dedicated crypto adapters Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 01/13] KVM: s390: Interface to test whether APXA installed Tony Krowiak
2018-05-16 10:21 ` Cornelia Huck
2018-05-16 10:45 ` Tony Krowiak
2018-05-17 9:11 ` Harald Freudenberger
2018-05-17 9:44 ` Cornelia Huck
2018-05-07 15:11 ` [PATCH v5 02/13] KVM: s390: refactor crypto initialization Tony Krowiak
2018-05-16 8:51 ` Pierre Morel
2018-05-16 11:14 ` Tony Krowiak
2018-05-16 12:17 ` Pierre Morel
2018-05-16 12:21 ` Cornelia Huck
2018-05-07 15:11 ` [PATCH v5 03/13] KVM: s390: CPU model support for AP virtualization Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP device driver Tony Krowiak
2018-05-16 8:21 ` Pierre Morel
2018-05-16 11:29 ` Tony Krowiak
2018-05-16 11:45 ` Tony Krowiak
2018-06-07 8:57 ` Pierre Morel
2018-06-13 7:41 ` Pierre Morel
2018-06-13 7:48 ` Cornelia Huck
2018-06-13 10:54 ` Pierre Morel
2018-06-13 11:14 ` Cornelia Huck
2018-06-13 12:01 ` Pierre Morel
2018-06-13 12:12 ` Cornelia Huck
2018-06-13 12:16 ` Pierre Morel
2018-06-14 13:04 ` Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 05/13] s390: vfio-ap: register matrix device with VFIO mdev framework Tony Krowiak
2018-05-11 17:18 ` Halil Pasic
2018-05-14 19:42 ` Tony Krowiak
2018-05-15 14:17 ` Pierre Morel
2018-05-15 15:16 ` Tony Krowiak
2018-05-15 15:48 ` Halil Pasic
2018-05-15 16:11 ` Tony Krowiak
2018-05-17 7:44 ` Cornelia Huck
2018-05-21 15:13 ` Tony Krowiak
2018-05-22 8:19 ` Cornelia Huck
2018-05-22 21:41 ` Tony Krowiak
2018-05-16 10:42 ` Cornelia Huck
2018-05-16 12:48 ` Tony Krowiak
2018-05-16 12:58 ` Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 06/13] KVM: s390: interfaces to manage guest's AP matrix Tony Krowiak
2018-05-11 16:08 ` Halil Pasic
2018-05-16 14:29 ` Tony Krowiak [this message]
2018-05-16 14:41 ` Pierre Morel
2018-05-21 15:23 ` Tony Krowiak
2018-05-15 14:55 ` Pierre Morel
2018-05-15 16:07 ` Tony Krowiak
2018-05-16 7:48 ` Pierre Morel
2018-05-16 13:12 ` Tony Krowiak
2018-05-16 13:15 ` Pierre Morel
2018-05-16 13:48 ` Tony Krowiak
2018-05-18 8:55 ` Pierre Morel
2018-05-23 14:29 ` Tony Krowiak
2018-05-24 7:46 ` Pierre Morel
2018-05-07 15:11 ` [PATCH v5 07/13] s390: vfio-ap: sysfs interfaces to configure adapters Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 08/13] s390: vfio-ap: sysfs interfaces to configure domains Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 09/13] s390: vfio-ap: sysfs interfaces to configure control domains Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 10/13] s390: vfio-ap: sysfs interface to view matrix mdev matrix Tony Krowiak
2018-05-16 7:55 ` Pierre Morel
2018-05-23 14:38 ` Tony Krowiak
2018-05-24 9:10 ` Pierre Morel
2018-05-30 14:28 ` Tony Krowiak
2018-06-05 12:40 ` Pierre Morel
2018-06-06 14:24 ` Tony Krowiak
2018-06-06 15:10 ` Pierre Morel
2018-06-07 12:53 ` Tony Krowiak
2018-06-07 13:16 ` Halil Pasic
2018-06-07 14:33 ` Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 11/13] KVM: s390: implement mediated device open callback Tony Krowiak
2018-05-16 8:03 ` Pierre Morel
2018-05-23 14:45 ` Tony Krowiak
2018-05-24 9:08 ` Pierre Morel
2018-05-30 14:33 ` Tony Krowiak
2018-06-05 12:19 ` Pierre Morel
2018-06-06 14:28 ` Tony Krowiak
2018-06-06 16:08 ` Pierre Morel
2018-06-06 17:40 ` Pierre Morel
2018-06-07 13:54 ` Tony Krowiak
2018-06-07 15:20 ` Pierre Morel
2018-06-07 16:30 ` Tony Krowiak
2018-06-07 17:15 ` Pierre Morel
2018-06-08 21:59 ` Tony Krowiak
2018-06-11 9:23 ` Pierre Morel
2018-06-11 11:32 ` Halil Pasic
2018-06-11 11:49 ` Janosch Frank
2018-06-11 16:26 ` Tony Krowiak
2018-06-11 16:50 ` Halil Pasic
2018-06-11 16:54 ` Tony Krowiak
2018-06-11 12:50 ` Tony Krowiak
2018-06-11 12:56 ` Tony Krowiak
2018-06-07 13:52 ` Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 12/13] s390: vfio-ap: implement VFIO_DEVICE_GET_INFO ioctl Tony Krowiak
2018-05-07 15:11 ` [PATCH v5 13/13] s390: doc: detailed specifications for AP virtualization Tony Krowiak
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