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Date: Wed, 5 Nov 2014 11:04:21 +0100
From: Antonios Motakis <a.motakis@...tualopensystems.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: kvm-arm <kvmarm@...ts.cs.columbia.edu>,
Linux IOMMU <iommu@...ts.linux-foundation.org>,
Will Deacon <will.deacon@....com>,
VirtualOpenSystems Technical Team <tech@...tualopensystems.com>,
Christoffer Dall <christoffer.dall@...aro.org>,
Eric Auger <eric.auger@...aro.org>,
Kim Phillips <kim.phillips@...escale.com>,
Marc Zyngier <marc.zyngier@....com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Alexander Gordeev <agordeev@...hat.com>,
"open list:VFIO DRIVER" <kvm@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 15/19] vfio: add local lock in virqfd instead of
depending on VFIO PCI
On Fri, Oct 31, 2014 at 8:43 PM, Alex Williamson
<alex.williamson@...hat.com> wrote:
> On Mon, 2014-10-27 at 19:08 +0100, Antonios Motakis wrote:
>> Virqfd just needs to keep accesses to any struct *virqfd safe, but this
>> comes into play only when creating or destroying eventfds, so sharing
>> the same spinlock with the VFIO bus driver is not necessary.
>>
>> Signed-off-by: Antonios Motakis <a.motakis@...tualopensystems.com>
>> ---
>> drivers/vfio/pci/vfio_pci_intrs.c | 10 +++++-----
>> drivers/vfio/virqfd.c | 24 +++++++++++++-----------
>> include/linux/vfio.h | 3 +--
>> 3 files changed, 19 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
>> index 3f909bb..e56c814 100644
>> --- a/drivers/vfio/pci/vfio_pci_intrs.c
>> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
>> @@ -226,8 +226,8 @@ static int vfio_intx_set_signal(struct vfio_pci_device *vdev, int fd)
>> static void vfio_intx_disable(struct vfio_pci_device *vdev)
>> {
>> vfio_intx_set_signal(vdev, -1);
>> - virqfd_disable(vdev, &vdev->ctx[0].unmask);
>> - virqfd_disable(vdev, &vdev->ctx[0].mask);
>> + virqfd_disable(&vdev->ctx[0].unmask);
>> + virqfd_disable(&vdev->ctx[0].mask);
>> vdev->irq_type = VFIO_PCI_NUM_IRQS;
>> vdev->num_ctx = 0;
>> kfree(vdev->ctx);
>> @@ -377,8 +377,8 @@ static void vfio_msi_disable(struct vfio_pci_device *vdev, bool msix)
>> vfio_msi_set_block(vdev, 0, vdev->num_ctx, NULL, msix);
>>
>> for (i = 0; i < vdev->num_ctx; i++) {
>> - virqfd_disable(vdev, &vdev->ctx[i].unmask);
>> - virqfd_disable(vdev, &vdev->ctx[i].mask);
>> + virqfd_disable(&vdev->ctx[i].unmask);
>> + virqfd_disable(&vdev->ctx[i].mask);
>> }
>>
>> if (msix) {
>> @@ -415,7 +415,7 @@ static int vfio_pci_set_intx_unmask(struct vfio_pci_device *vdev,
>> vfio_send_intx_eventfd, NULL,
>> &vdev->ctx[0].unmask, fd);
>>
>> - virqfd_disable(vdev, &vdev->ctx[0].unmask);
>> + virqfd_disable(&vdev->ctx[0].unmask);
>> }
>>
>> return 0;
>> diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
>> index 243eb61..27fa2f0 100644
>> --- a/drivers/vfio/virqfd.c
>> +++ b/drivers/vfio/virqfd.c
>> @@ -17,6 +17,7 @@
>> #include "pci/vfio_pci_private.h"
>>
>> static struct workqueue_struct *vfio_irqfd_cleanup_wq;
>> +static spinlock_t lock;
>
> Define this as:
>
> DEFINE_SPINLOCK(lock);
>
> and we can avoid needing the init.
Ack, thanks.
>
>> int __init vfio_pci_virqfd_init(void)
>> {
>> @@ -25,6 +26,8 @@ int __init vfio_pci_virqfd_init(void)
>> if (!vfio_irqfd_cleanup_wq)
>> return -ENOMEM;
>>
>> + spin_lock_init(&lock);
>> +
>> return 0;
>> }
>>
>> @@ -53,21 +56,21 @@ static int virqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
>>
>> if (flags & POLLHUP) {
>> unsigned long flags;
>> - spin_lock_irqsave(&virqfd->vdev->irqlock, flags);
>> + spin_lock_irqsave(&lock, flags);
>>
>> /*
>> * The eventfd is closing, if the virqfd has not yet been
>> * queued for release, as determined by testing whether the
>> - * vdev pointer to it is still valid, queue it now. As
>> + * virqfd pointer to it is still valid, queue it now. As
>> * with kvm irqfds, we know we won't race against the virqfd
>> - * going away because we hold wqh->lock to get here.
>> + * going away because we hold the lock to get here.
>> */
>> if (*(virqfd->pvirqfd) == virqfd) {
>> *(virqfd->pvirqfd) = NULL;
>> virqfd_deactivate(virqfd);
>> }
>>
>> - spin_unlock_irqrestore(&virqfd->vdev->irqlock, flags);
>> + spin_unlock_irqrestore(&lock, flags);
>> }
>>
>> return 0;
>> @@ -143,16 +146,16 @@ int virqfd_enable(struct vfio_pci_device *vdev,
>> * we update the pointer to the virqfd under lock to avoid
>> * pushing multiple jobs to release the same virqfd.
>> */
>> - spin_lock_irq(&vdev->irqlock);
>> + spin_lock_irq(&lock);
>>
>> if (*pvirqfd) {
>> - spin_unlock_irq(&vdev->irqlock);
>> + spin_unlock_irq(&lock);
>> ret = -EBUSY;
>> goto err_busy;
>> }
>> *pvirqfd = virqfd;
>>
>> - spin_unlock_irq(&vdev->irqlock);
>> + spin_unlock_irq(&lock);
>>
>> /*
>> * Install our own custom wake-up handling so we are notified via
>> @@ -190,19 +193,18 @@ err_fd:
>> }
>> EXPORT_SYMBOL_GPL(virqfd_enable);
>>
>> -void virqfd_disable(struct vfio_pci_device *vdev,
>> - struct virqfd **pvirqfd)
>> +void virqfd_disable(struct virqfd **pvirqfd)
>> {
>> unsigned long flags;
>>
>> - spin_lock_irqsave(&vdev->irqlock, flags);
>> + spin_lock_irqsave(&lock, flags);
>>
>> if (*pvirqfd) {
>> virqfd_deactivate(*pvirqfd);
>> *pvirqfd = NULL;
>> }
>>
>> - spin_unlock_irqrestore(&vdev->irqlock, flags);
>> + spin_unlock_irqrestore(&lock, flags);
>>
>> /*
>> * Block until we know all outstanding shutdown jobs have completed.
>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>> index a077c48..fb6037b 100644
>> --- a/include/linux/vfio.h
>> +++ b/include/linux/vfio.h
>> @@ -146,7 +146,6 @@ extern int virqfd_enable(struct vfio_pci_device *vdev,
>> int (*handler)(struct vfio_pci_device *, void *),
>> void (*thread)(struct vfio_pci_device *, void *),
>> void *data, struct virqfd **pvirqfd, int fd);
>> -extern void virqfd_disable(struct vfio_pci_device *vdev,
>> - struct virqfd **pvirqfd);
>> +extern void virqfd_disable(struct virqfd **pvirqfd);
>>
>> #endif /* VFIO_H */
>
>
>
--
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