* [PATCH] vfio: call irq_bypass_unregister_producer() before freeing irq
@ 2019-11-27 16:49 Jiang Yi
2019-11-27 18:20 ` Marc Zyngier
2019-11-28 10:01 ` Auger Eric
0 siblings, 2 replies; 4+ messages in thread
From: Jiang Yi @ 2019-11-27 16:49 UTC (permalink / raw)
To: kvm; +Cc: adulea, jschoenh, maz, alex.williamson, cohuck, Jiang Yi
Since irq_bypass_register_producer() is called after request_irq(), we
should do tear-down in reverse order: irq_bypass_unregister_producer()
then free_irq().
Signed-off-by: Jiang Yi <giangyi@amazon.com>
---
drivers/vfio/pci/vfio_pci_intrs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 3fa3f728fb39..2056f3f85f59 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -289,18 +289,18 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
int irq, ret;
if (vector < 0 || vector >= vdev->num_ctx)
return -EINVAL;
irq = pci_irq_vector(pdev, vector);
if (vdev->ctx[vector].trigger) {
- free_irq(irq, vdev->ctx[vector].trigger);
irq_bypass_unregister_producer(&vdev->ctx[vector].producer);
+ free_irq(irq, vdev->ctx[vector].trigger);
kfree(vdev->ctx[vector].name);
eventfd_ctx_put(vdev->ctx[vector].trigger);
vdev->ctx[vector].trigger = NULL;
}
if (fd < 0)
return 0;
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] vfio: call irq_bypass_unregister_producer() before freeing irq
2019-11-27 16:49 [PATCH] vfio: call irq_bypass_unregister_producer() before freeing irq Jiang Yi
@ 2019-11-27 18:20 ` Marc Zyngier
2019-12-02 23:14 ` Alex Williamson
2019-11-28 10:01 ` Auger Eric
1 sibling, 1 reply; 4+ messages in thread
From: Marc Zyngier @ 2019-11-27 18:20 UTC (permalink / raw)
To: Jiang Yi; +Cc: kvm, adulea, jschoenh, alex.williamson, cohuck
On Wed, 27 Nov 2019 16:49:10 +0000,
Jiang Yi <giangyi@amazon.com> wrote:
Hi Jiang,
Thanks for spotting this!
> Since irq_bypass_register_producer() is called after request_irq(), we
> should do tear-down in reverse order: irq_bypass_unregister_producer()
> then free_irq().
More importantly, free_irq() is going to releases resources that can
still be required by the del_producer callback. Notably, for arm64 and
GICv4:
free_irq(irq)
__free_irq(irq)
irq_domain_deactivate_irq(irq)
its_irq_domain_deactivate()
[unmap the VLPI from the ITS]
kvm_arch_irq_bypass_del_producer(cons, prod)
kvm_vgic_v4_unset_forwarding(kvm, irq, ...)
its_unmap_vlpi(irq)
[Unmap the VLPI from the ITS (again), remap the original LPI]
which isn't great, and has the potential to wedge the HW. Reversing
the two makes more sense: Unmap the VLPI, remap the LPI, and finally
unmap the LPI. I haven't checked what it does with VT-D.
> Signed-off-by: Jiang Yi <giangyi@amazon.com>
> ---
> drivers/vfio/pci/vfio_pci_intrs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 3fa3f728fb39..2056f3f85f59 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -289,18 +289,18 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
> int irq, ret;
>
> if (vector < 0 || vector >= vdev->num_ctx)
> return -EINVAL;
>
> irq = pci_irq_vector(pdev, vector);
>
> if (vdev->ctx[vector].trigger) {
> - free_irq(irq, vdev->ctx[vector].trigger);
> irq_bypass_unregister_producer(&vdev->ctx[vector].producer);
> + free_irq(irq, vdev->ctx[vector].trigger);
> kfree(vdev->ctx[vector].name);
> eventfd_ctx_put(vdev->ctx[vector].trigger);
> vdev->ctx[vector].trigger = NULL;
> }
>
> if (fd < 0)
> return 0;
>
> --
> 2.17.1
>
>
FWIW:
Cc: stable@vger.kernel.org # v4.4+
Fixes: 6d7425f109d26 ("vfio: Register/unregister irq_bypass_producer")
Reviewed-by: Marc Zyngier <maz@kernel.org>
Thanks again,
M.
--
Jazz is not dead, it just smells funny.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] vfio: call irq_bypass_unregister_producer() before freeing irq
2019-11-27 16:49 [PATCH] vfio: call irq_bypass_unregister_producer() before freeing irq Jiang Yi
2019-11-27 18:20 ` Marc Zyngier
@ 2019-11-28 10:01 ` Auger Eric
1 sibling, 0 replies; 4+ messages in thread
From: Auger Eric @ 2019-11-28 10:01 UTC (permalink / raw)
To: Jiang Yi, kvm; +Cc: adulea, jschoenh, maz, alex.williamson, cohuck
Hi,
On 11/27/19 5:49 PM, Jiang Yi wrote:
> Since irq_bypass_register_producer() is called after request_irq(), we
> should do tear-down in reverse order: irq_bypass_unregister_producer()
> then free_irq().
>
> Signed-off-by: Jiang Yi <giangyi@amazon.com>
> ---
> drivers/vfio/pci/vfio_pci_intrs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 3fa3f728fb39..2056f3f85f59 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -289,18 +289,18 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
> int irq, ret;
>
> if (vector < 0 || vector >= vdev->num_ctx)
> return -EINVAL;
>
> irq = pci_irq_vector(pdev, vector);
>
> if (vdev->ctx[vector].trigger) {
> - free_irq(irq, vdev->ctx[vector].trigger);
> irq_bypass_unregister_producer(&vdev->ctx[vector].producer);
> + free_irq(irq, vdev->ctx[vector].trigger);
Looks the right way too
Reviewed-by: Eric Auger <eric.auger@redhat.com>
May be worth checking it does not alter the x86 posted interrupt setup
though. update_pi_irte() gets called. I was concerned about the fact the
interrupts may be enabled when doing the unregistration (TBC). The
irq_bypass framework offers producer start/stop callbacks that would
allow to handle this but nobody use them atm.
Thanks
Eric
> kfree(vdev->ctx[vector].name);
> eventfd_ctx_put(vdev->ctx[vector].trigger);
> vdev->ctx[vector].trigger = NULL;
> }
>
> if (fd < 0)
> return 0;
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] vfio: call irq_bypass_unregister_producer() before freeing irq
2019-11-27 18:20 ` Marc Zyngier
@ 2019-12-02 23:14 ` Alex Williamson
0 siblings, 0 replies; 4+ messages in thread
From: Alex Williamson @ 2019-12-02 23:14 UTC (permalink / raw)
To: Marc Zyngier
Cc: Jiang Yi, kvm, adulea, jschoenh, cohuck, Suthikulpanit, Suravee,
Singh, Brijesh, Lendacky, Thomas, Raj, Ashok, Tian, Kevin,
Paul Mackerras, Michael Ellerman
On Wed, 27 Nov 2019 18:20:14 +0000
Marc Zyngier <maz@kernel.org> wrote:
> On Wed, 27 Nov 2019 16:49:10 +0000,
> Jiang Yi <giangyi@amazon.com> wrote:
>
> Hi Jiang,
>
> Thanks for spotting this!
>
> > Since irq_bypass_register_producer() is called after request_irq(), we
> > should do tear-down in reverse order: irq_bypass_unregister_producer()
> > then free_irq().
>
> More importantly, free_irq() is going to releases resources that can
> still be required by the del_producer callback. Notably, for arm64 and
> GICv4:
>
> free_irq(irq)
> __free_irq(irq)
> irq_domain_deactivate_irq(irq)
> its_irq_domain_deactivate()
> [unmap the VLPI from the ITS]
>
> kvm_arch_irq_bypass_del_producer(cons, prod)
> kvm_vgic_v4_unset_forwarding(kvm, irq, ...)
> its_unmap_vlpi(irq)
> [Unmap the VLPI from the ITS (again), remap the original LPI]
>
> which isn't great, and has the potential to wedge the HW. Reversing
> the two makes more sense: Unmap the VLPI, remap the LPI, and finally
> unmap the LPI. I haven't checked what it does with VT-D.
Yep, it seems a lot safer to reverse this but we need to incorporate
some of Marc's rationale above into the commit log to justify the
stable and fixes tags. Here's an attempt:
--
free_irq() may release resources required by the irqbypass
del_producer() callback. Notably on arm64 with GICv4:
free_irq(irq)
__free_irq(irq)
irq_domain_deactivate_irq(irq)
its_irq_domain_deactivate()
[unmap the VLPI from the ITS]
kvm_arch_irq_bypass_del_producer(cons, prod)
kvm_vgic_v4_unset_forwarding(kvm, irq, ...)
its_unmap_vlpi(irq)
[Unmap the VLPI from the ITS (again), remap the original LPI]
This has the potential to wedge hardware. Re-order to free the IRQ
after unregistering the irqbypass producer, which also provides the
proper mirror of setup ordering.
--
Cc'ing some usual suspects from AMD, Intel, and Power where the
kvm_arch_irq_bypass_del_producer() callback is also implemented.
Thanks,
Alex
> > Signed-off-by: Jiang Yi <giangyi@amazon.com>
> > ---
> > drivers/vfio/pci/vfio_pci_intrs.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> > index 3fa3f728fb39..2056f3f85f59 100644
> > --- a/drivers/vfio/pci/vfio_pci_intrs.c
> > +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> > @@ -289,18 +289,18 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
> > int irq, ret;
> >
> > if (vector < 0 || vector >= vdev->num_ctx)
> > return -EINVAL;
> >
> > irq = pci_irq_vector(pdev, vector);
> >
> > if (vdev->ctx[vector].trigger) {
> > - free_irq(irq, vdev->ctx[vector].trigger);
> > irq_bypass_unregister_producer(&vdev->ctx[vector].producer);
> > + free_irq(irq, vdev->ctx[vector].trigger);
> > kfree(vdev->ctx[vector].name);
> > eventfd_ctx_put(vdev->ctx[vector].trigger);
> > vdev->ctx[vector].trigger = NULL;
> > }
> >
> > if (fd < 0)
> > return 0;
> >
> > --
> > 2.17.1
> >
> >
>
> FWIW:
>
> Cc: stable@vger.kernel.org # v4.4+
> Fixes: 6d7425f109d26 ("vfio: Register/unregister irq_bypass_producer")
> Reviewed-by: Marc Zyngier <maz@kernel.org>
>
> Thanks again,
>
> M.
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-12-02 23:14 UTC | newest]
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2019-11-27 16:49 [PATCH] vfio: call irq_bypass_unregister_producer() before freeing irq Jiang Yi
2019-11-27 18:20 ` Marc Zyngier
2019-12-02 23:14 ` Alex Williamson
2019-11-28 10:01 ` Auger Eric
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