* [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference
@ 2017-03-27 4:40 Alexey Kardashevskiy
2017-03-27 15:28 ` Paolo Bonzini
2017-03-29 2:40 ` Jason Wang
0 siblings, 2 replies; 6+ messages in thread
From: Alexey Kardashevskiy @ 2017-03-27 4:40 UTC (permalink / raw)
To: qemu-devel
Cc: Alexey Kardashevskiy, David Gibson, Marcel Apfelbaum,
Michael S . Tsirkin, Paolo Bonzini, Jason Wang, Peter Maydell
The recent introduction of a bus master container added
memory_region_add_subregion() into the PCI device registering path but
missed memory_region_del_subregion() in the unregistering path leaving
a reference to the root memory region of the new container.
This adds missing memory_region_del_subregion().
Fixes: 3716d5902d743 ("pci: introduce a bus master container")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
hw/pci/pci.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index e6b08e1988..bd8043c460 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -869,6 +869,8 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
pci_dev->bus->devices[pci_dev->devfn] = NULL;
pci_config_free(pci_dev);
+ memory_region_del_subregion(&pci_dev->bus_master_container_region,
+ &pci_dev->bus_master_enable_region);
address_space_destroy(&pci_dev->bus_master_as);
}
--
2.11.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference
2017-03-27 4:40 [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference Alexey Kardashevskiy
@ 2017-03-27 15:28 ` Paolo Bonzini
2017-03-28 0:06 ` David Gibson
2017-03-29 2:40 ` Jason Wang
1 sibling, 1 reply; 6+ messages in thread
From: Paolo Bonzini @ 2017-03-27 15:28 UTC (permalink / raw)
To: Alexey Kardashevskiy, qemu-devel
Cc: David Gibson, Marcel Apfelbaum, Michael S . Tsirkin, Jason Wang,
Peter Maydell
On 27/03/2017 06:40, Alexey Kardashevskiy wrote:
> The recent introduction of a bus master container added
> memory_region_add_subregion() into the PCI device registering path but
> missed memory_region_del_subregion() in the unregistering path leaving
> a reference to the root memory region of the new container.
>
> This adds missing memory_region_del_subregion().
>
> Fixes: 3716d5902d743 ("pci: introduce a bus master container")
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> hw/pci/pci.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index e6b08e1988..bd8043c460 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -869,6 +869,8 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
> pci_dev->bus->devices[pci_dev->devfn] = NULL;
> pci_config_free(pci_dev);
>
> + memory_region_del_subregion(&pci_dev->bus_master_container_region,
> + &pci_dev->bus_master_enable_region);
> address_space_destroy(&pci_dev->bus_master_as);
> }
>
>
My own review fail. The enable subregion would be deleted when a memory
region is finalized, but the enable subregions is keeping the owner
alive. And until the owner is alive, the container region is not
deleted either. So there is a reference count cycle, which we need to
break.
It's probably good to revisit commit 2e2b8eb ("memory: allow destroying
a non-empty MemoryRegion", 2015-10-01). For 2.9,
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Paolo
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference
2017-03-27 15:28 ` Paolo Bonzini
@ 2017-03-28 0:06 ` David Gibson
2017-03-28 2:33 ` Michael S. Tsirkin
0 siblings, 1 reply; 6+ messages in thread
From: David Gibson @ 2017-03-28 0:06 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Alexey Kardashevskiy, qemu-devel, Marcel Apfelbaum,
Michael S . Tsirkin, Jason Wang, Peter Maydell
[-- Attachment #1: Type: text/plain, Size: 1933 bytes --]
On Mon, Mar 27, 2017 at 05:28:17PM +0200, Paolo Bonzini wrote:
>
>
> On 27/03/2017 06:40, Alexey Kardashevskiy wrote:
> > The recent introduction of a bus master container added
> > memory_region_add_subregion() into the PCI device registering path but
> > missed memory_region_del_subregion() in the unregistering path leaving
> > a reference to the root memory region of the new container.
> >
> > This adds missing memory_region_del_subregion().
> >
> > Fixes: 3716d5902d743 ("pci: introduce a bus master container")
> > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > ---
> > hw/pci/pci.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index e6b08e1988..bd8043c460 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -869,6 +869,8 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
> > pci_dev->bus->devices[pci_dev->devfn] = NULL;
> > pci_config_free(pci_dev);
> >
> > + memory_region_del_subregion(&pci_dev->bus_master_container_region,
> > + &pci_dev->bus_master_enable_region);
> > address_space_destroy(&pci_dev->bus_master_as);
> > }
> >
> >
>
> My own review fail. The enable subregion would be deleted when a memory
> region is finalized, but the enable subregions is keeping the owner
> alive. And until the owner is alive, the container region is not
> deleted either. So there is a reference count cycle, which we need to
> break.
>
> It's probably good to revisit commit 2e2b8eb ("memory: allow destroying
> a non-empty MemoryRegion", 2015-10-01). For 2.9,
>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Merged to ppc-for-2.9.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference
2017-03-28 0:06 ` David Gibson
@ 2017-03-28 2:33 ` Michael S. Tsirkin
2017-03-28 2:47 ` David Gibson
0 siblings, 1 reply; 6+ messages in thread
From: Michael S. Tsirkin @ 2017-03-28 2:33 UTC (permalink / raw)
To: David Gibson
Cc: Paolo Bonzini, Alexey Kardashevskiy, qemu-devel,
Marcel Apfelbaum, Jason Wang, Peter Maydell
On Tue, Mar 28, 2017 at 11:06:28AM +1100, David Gibson wrote:
> On Mon, Mar 27, 2017 at 05:28:17PM +0200, Paolo Bonzini wrote:
> >
> >
> > On 27/03/2017 06:40, Alexey Kardashevskiy wrote:
> > > The recent introduction of a bus master container added
> > > memory_region_add_subregion() into the PCI device registering path but
> > > missed memory_region_del_subregion() in the unregistering path leaving
> > > a reference to the root memory region of the new container.
> > >
> > > This adds missing memory_region_del_subregion().
> > >
> > > Fixes: 3716d5902d743 ("pci: introduce a bus master container")
> > > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > > ---
> > > hw/pci/pci.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > > index e6b08e1988..bd8043c460 100644
> > > --- a/hw/pci/pci.c
> > > +++ b/hw/pci/pci.c
> > > @@ -869,6 +869,8 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
> > > pci_dev->bus->devices[pci_dev->devfn] = NULL;
> > > pci_config_free(pci_dev);
> > >
> > > + memory_region_del_subregion(&pci_dev->bus_master_container_region,
> > > + &pci_dev->bus_master_enable_region);
> > > address_space_destroy(&pci_dev->bus_master_as);
> > > }
> > >
> > >
> >
> > My own review fail. The enable subregion would be deleted when a memory
> > region is finalized, but the enable subregions is keeping the owner
> > alive. And until the owner is alive, the container region is not
> > deleted either. So there is a reference count cycle, which we need to
> > break.
> >
> > It's probably good to revisit commit 2e2b8eb ("memory: allow destroying
> > a non-empty MemoryRegion", 2015-10-01). For 2.9,
> >
> > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
>
> Merged to ppc-for-2.9.
I have it on pci branch, seems more appropriate.
> --
> David Gibson | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
> | _way_ _around_!
> http://www.ozlabs.org/~dgibson
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference
2017-03-28 2:33 ` Michael S. Tsirkin
@ 2017-03-28 2:47 ` David Gibson
0 siblings, 0 replies; 6+ messages in thread
From: David Gibson @ 2017-03-28 2:47 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Paolo Bonzini, Alexey Kardashevskiy, qemu-devel,
Marcel Apfelbaum, Jason Wang, Peter Maydell
[-- Attachment #1: Type: text/plain, Size: 2345 bytes --]
On Tue, Mar 28, 2017 at 05:33:48AM +0300, Michael S. Tsirkin wrote:
> On Tue, Mar 28, 2017 at 11:06:28AM +1100, David Gibson wrote:
> > On Mon, Mar 27, 2017 at 05:28:17PM +0200, Paolo Bonzini wrote:
> > >
> > >
> > > On 27/03/2017 06:40, Alexey Kardashevskiy wrote:
> > > > The recent introduction of a bus master container added
> > > > memory_region_add_subregion() into the PCI device registering path but
> > > > missed memory_region_del_subregion() in the unregistering path leaving
> > > > a reference to the root memory region of the new container.
> > > >
> > > > This adds missing memory_region_del_subregion().
> > > >
> > > > Fixes: 3716d5902d743 ("pci: introduce a bus master container")
> > > > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> > > > ---
> > > > hw/pci/pci.c | 2 ++
> > > > 1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > > > index e6b08e1988..bd8043c460 100644
> > > > --- a/hw/pci/pci.c
> > > > +++ b/hw/pci/pci.c
> > > > @@ -869,6 +869,8 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
> > > > pci_dev->bus->devices[pci_dev->devfn] = NULL;
> > > > pci_config_free(pci_dev);
> > > >
> > > > + memory_region_del_subregion(&pci_dev->bus_master_container_region,
> > > > + &pci_dev->bus_master_enable_region);
> > > > address_space_destroy(&pci_dev->bus_master_as);
> > > > }
> > > >
> > > >
> > >
> > > My own review fail. The enable subregion would be deleted when a memory
> > > region is finalized, but the enable subregions is keeping the owner
> > > alive. And until the owner is alive, the container region is not
> > > deleted either. So there is a reference count cycle, which we need to
> > > break.
> > >
> > > It's probably good to revisit commit 2e2b8eb ("memory: allow destroying
> > > a non-empty MemoryRegion", 2015-10-01). For 2.9,
> > >
> > > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> >
> > Merged to ppc-for-2.9.
>
> I have it on pci branch, seems more appropriate.
Good point. I've dropped it from my tree.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
[-- Attachment #2: signature.asc --]
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference
2017-03-27 4:40 [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference Alexey Kardashevskiy
2017-03-27 15:28 ` Paolo Bonzini
@ 2017-03-29 2:40 ` Jason Wang
1 sibling, 0 replies; 6+ messages in thread
From: Jason Wang @ 2017-03-29 2:40 UTC (permalink / raw)
To: Alexey Kardashevskiy, qemu-devel
Cc: David Gibson, Marcel Apfelbaum, Michael S . Tsirkin,
Paolo Bonzini, Peter Maydell
On 2017年03月27日 12:40, Alexey Kardashevskiy wrote:
> The recent introduction of a bus master container added
> memory_region_add_subregion() into the PCI device registering path but
> missed memory_region_del_subregion() in the unregistering path leaving
> a reference to the root memory region of the new container.
>
> This adds missing memory_region_del_subregion().
>
> Fixes: 3716d5902d743 ("pci: introduce a bus master container")
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> hw/pci/pci.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index e6b08e1988..bd8043c460 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -869,6 +869,8 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
> pci_dev->bus->devices[pci_dev->devfn] = NULL;
> pci_config_free(pci_dev);
>
> + memory_region_del_subregion(&pci_dev->bus_master_container_region,
> + &pci_dev->bus_master_enable_region);
> address_space_destroy(&pci_dev->bus_master_as);
> }
>
Acked-by: Jason Wang <jasowang@redhat.com>
Thanks!
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-03-29 2:41 UTC | newest]
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2017-03-27 4:40 [Qemu-devel] [PATCH qemu] pci: Add missing drop of bus master AS reference Alexey Kardashevskiy
2017-03-27 15:28 ` Paolo Bonzini
2017-03-28 0:06 ` David Gibson
2017-03-28 2:33 ` Michael S. Tsirkin
2017-03-28 2:47 ` David Gibson
2017-03-29 2:40 ` Jason Wang
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