Re: [PATCH v4 5/7] s390: ap: implement PAPQ AQIC interception in kernel

[Pierre Morel]

On 26/02/2019 19:23, Tony Krowiak wrote:
> On 2/22/19 10:29 AM, Pierre Morel wrote:
> > We register the AP PQAP instruction hook during the open
> > of the mediated device. And unregister it on release.
> >
> > In the AP PQAP instruction hook, if we receive a demand to
> > enable IRQs,
> > - we retrieve the vfio_ap_queue based on the APQN we receive
> > ÂÂ in REG1,
> > - we retrieve the page of the guest address, (NIB), from
> > ÂÂ register REG2
> > - we the mediated device to use the VFIO pinning infratrsucture
> > ÂÂ to pin the page of the guest address,
> > - we retrieve the pointer to KVM to register the guest ISC
> > ÂÂ and retrieve the host ISC
> > - finaly we activate GISA
> >
> > If we receive a demand to disable IRQs,
> > - we deactivate GISA
> > - unregister from the GIB
> > - unping the NIB
> >
> > Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> > ---
> > Â arch/s390/include/asm/kvm_host.hÂÂÂÂÂ |ÂÂ 1 +
> > Â drivers/s390/crypto/ap_bus.hÂÂÂÂÂÂÂÂÂ |ÂÂ 1 +
> > Â drivers/s390/crypto/vfio_ap_ops.cÂÂÂÂ | 199 
> > +++++++++++++++++++++++++++++++++-
> > Â drivers/s390/crypto/vfio_ap_private.h |ÂÂ 1 +
> > Â 4 files changed, 199 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/s390/include/asm/kvm_host.h 
> > b/arch/s390/include/asm/kvm_host.h
> > index 49cc8b0..5f3bb8c 100644
> > --- a/arch/s390/include/asm/kvm_host.h
> > +++ b/arch/s390/include/asm/kvm_host.h
> > @@ -720,6 +720,7 @@ struct kvm_s390_cpu_model {
> > Â struct kvm_s390_crypto {
> > ÂÂÂÂÂ struct kvm_s390_crypto_cb *crycb;
> > ÂÂÂÂÂ int (*pqap_hook)(struct kvm_vcpu *vcpu);
> > +ÂÂÂ void *vfio_private;

...snip...


> > + *
> > + * Return 0 if we could handle the request inside KVM.
> > + * otherwise, returns -EOPNOTSUPP to let QEMU handle the fault.
> > + */
> > +static int handle_pqap(struct kvm_vcpu *vcpu)
>
> Change this function name to handle_pqap_aqic

Since we only intercept AQIC, why not.

> > +{
> > +}
>
> Add this function:
>
> static int handle_pqap(struct kvm_vcpu *vcpu)
> {
>  ÂÂÂÂint ret;
>  ÂÂÂÂuint8_t fc;
>
>  ÂÂÂÂfc = vcpu->run->s.regs.gprs[0] >> 24;
>  ÂÂÂÂswitch (fc) {
>  ÂÂÂÂcase 0x03:
>  ÂÂÂÂÂÂÂ ret = handle_pqap_aqic(vcpu);
>  ÂÂÂÂÂÂÂ break;
>  ÂÂÂÂdefault:
>  ÂÂÂÂÂÂÂ ret = -EOPNOTSUPP;
>  ÂÂÂÂÂÂÂ break;
>  ÂÂÂÂ}
>
>  ÂÂÂÂreturn ret;
> }

It is of no use for now, we only intercept AQIC, why introduce this now?

We can introduce a trampoline when we intercept TAPQ. If we do.


> > +
> > + /*
> > ÂÂ * vfio_ap_mdev_iommu_notifier: IOMMU notifier callback
> > ÂÂ *
> > ÂÂ * @nb: The notifier block
> > @@ -767,9 +950,10 @@ static int vfio_ap_mdev_iommu_notifier(struct 
> > notifier_block *nb,
> > ÂÂÂÂÂ if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) {
> > ÂÂÂÂÂÂÂÂÂ struct vfio_iommu_type1_dma_unmap *unmap = data;
> > -ÂÂÂÂÂÂÂ unsigned long g_pfn = unmap->iova >> PAGE_SHIFT;
> > +ÂÂÂÂÂÂÂ unsigned long pfn = unmap->iova >> PAGE_SHIFT;
> > -ÂÂÂÂÂÂÂ vfio_unpin_pages(mdev_dev(matrix_mdev->mdev), &g_pfn, 1);
> > +ÂÂÂÂÂÂÂ if (matrix_mdev->mdev)
> > +ÂÂÂÂÂÂÂÂÂÂÂ vfio_unpin_pages(mdev_dev(matrix_mdev->mdev), &pfn, 1);
> > ÂÂÂÂÂÂÂÂÂ return NOTIFY_OK;
> > ÂÂÂÂÂ }
> > @@ -879,6 +1063,11 @@ static int vfio_ap_mdev_open(struct mdev_device 
> > *mdev)
> > ÂÂÂÂÂ if (ret)
> > ÂÂÂÂÂÂÂÂÂ goto err_group;
> > +ÂÂÂ if (!matrix_mdev->kvm) {
> > +ÂÂÂÂÂÂÂ ret = -ENODEV;
> > +ÂÂÂÂÂÂÂ goto err_iommu;
> > +ÂÂÂ }
> > +
> > ÂÂÂÂÂ matrix_mdev->iommu_notifier.notifier_call = 
> > vfio_ap_mdev_iommu_notifier;
> > ÂÂÂÂÂ events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
> > @@ -887,6 +1076,8 @@ static int vfio_ap_mdev_open(struct mdev_device 
> > *mdev)
> > ÂÂÂÂÂ if (ret)
> > ÂÂÂÂÂÂÂÂÂ goto err_iommu;
> > +ÂÂÂ matrix_mdev->kvm->arch.crypto.pqap_hook = handle_pqap;
> > +ÂÂÂ matrix_mdev->kvm->arch.crypto.vfio_private = matrix_mdev;
>
> I do not see this used anywhere, why do we need it?

In handle_papq to retrieve the associated mediated device

> > ÂÂÂÂÂ return 0;
> > Â err_iommu:
> > @@ -905,6 +1096,8 @@ static void vfio_ap_mdev_release(struct 
> > mdev_device *mdev)
> > ÂÂÂÂÂÂÂÂÂ kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
> > ÂÂÂÂÂ vfio_ap_mdev_reset_queues(mdev);
> > +ÂÂÂ matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
> > +ÂÂÂ matrix_mdev->kvm->arch.crypto.vfio_private = NULL;
>
> Ditto

ditto

> > ÂÂÂÂÂ vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ &matrix_mdev->group_notifier);
> > ÂÂÂÂÂ vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> > diff --git a/drivers/s390/crypto/vfio_ap_private.h 
> > b/drivers/s390/crypto/vfio_ap_private.h
> > index e535735..e2fd2c0 100644
> > --- a/drivers/s390/crypto/vfio_ap_private.h
> > +++ b/drivers/s390/crypto/vfio_ap_private.h
> > @@ -94,6 +94,7 @@ struct vfio_ap_queue {
> > ÂÂÂÂÂ struct list_head list;
> > ÂÂÂÂÂ struct ap_matrix_mdev *matrix_mdev;
> > ÂÂÂÂÂ unsigned long nib;
> > +ÂÂÂ unsigned long g_pfn;
>
> Can't this be calculated from the nib?

It is.
It is initialized during the IRQ enabling with the current pinned NIB.
While the nib is initialised with the NIB to be use.

This allows to unpin the previous pinned NIB in the case the guest reset 
the queue, which automatically disable interrupt, because in this case 
the guest will not explicitely disable IRQ by using AQIC.


Regards,
Pierre


--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany