Re: [Qemu-devel] [PATCH RFC v11 4/4] vfio: add 'aer' property to expose aercap

[Alex Williamson]

On Fri, 20 Jan 2017 14:04:08 +0800
Cao jin  wrote:

> On 01/19/2017 06:36 AM, Alex Williamson wrote:
> > On Sat, 31 Dec 2016 17:13:08 +0800
> > Cao jin  wrote:
> >   
> >> From: Chen Fan 
> >>
> >> Add 'aer' property, let user choose whether expose the aer capability
> >> or not.  
> > 
> > But that's not what it does, it only controls the behavior in response
> > to non-fatal errors, the capability is exposed regardless.
> >   
> 
> This commit log is legacy, and defaults to off is a result of the
> configuration restriction & your previous discussion, right?
> 
> In current version, if 'aer' property is off, we just allocate the
> config space via pcie_add_capability(), we don't init the AER
> capability, the value is all 0s there, so does that still mean
> "capability is exposed regardless"?

The design has changed, we no longer require a matching host and guest
topology, we can more easily transparently enable non-fatal error
correction.  We need to reevaluate whether previous decisions are still
valid, we cannot blindly assume that a requirement for a previous
design still applies.  Thanks,

Alex
 
> >> Should disable aer feature by default, because only non-fatal
> >> error is supported now.   
> > 
> > Why does that mean it should be disabled by default?  What bad thing
> > happens if we enable this opportunistically?
> >   
> >> Signed-off-by: Chen Fan 
> >> Signed-off-by: Dou Liyang 
> >> Signed-off-by: Cao jin 
> >> ---
> >>  hw/vfio/pci.c | 2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> >> index 9861f72..fc9db66 100644
> >> --- a/hw/vfio/pci.c
> >> +++ b/hw/vfio/pci.c
> >> @@ -3057,6 +3057,8 @@ static Property vfio_pci_dev_properties[] = {
> >>  DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
> >> sub_device_id, PCI_ANY_ID),
> >>  DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 0),
> >> +DEFINE_PROP_BIT("aer", VFIOPCIDevice, features,
> >> +VFIO_FEATURE_ENABLE_AER_BIT, false),
> >>  /*
> >>   * TODO - support passed fds... is this necessary?
> >>   * DEFINE_PROP_STRING("vfiofd", VFIOPCIDevice, vfiofd_name),  
> > 
> > 
> > 
> > .
> >   
> 

Re: [Qemu-devel] [PATCH RFC v11 4/4] vfio: add 'aer' property to expose aercap

[Cao jin]

On 01/19/2017 06:36 AM, Alex Williamson wrote:
> On Sat, 31 Dec 2016 17:13:08 +0800
> Cao jin  wrote:
> 
>> From: Chen Fan 
>>
>> Add 'aer' property, let user choose whether expose the aer capability
>> or not.
> 
> But that's not what it does, it only controls the behavior in response
> to non-fatal errors, the capability is exposed regardless.
> 

This commit log is legacy, and defaults to off is a result of the
configuration restriction & your previous discussion, right?

In current version, if 'aer' property is off, we just allocate the
config space via pcie_add_capability(), we don't init the AER
capability, the value is all 0s there, so does that still mean
"capability is exposed regardless"?

>> Should disable aer feature by default, because only non-fatal
>> error is supported now. 
> 
> Why does that mean it should be disabled by default?  What bad thing
> happens if we enable this opportunistically?
> 
>> Signed-off-by: Chen Fan 
>> Signed-off-by: Dou Liyang 
>> Signed-off-by: Cao jin 
>> ---
>>  hw/vfio/pci.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index 9861f72..fc9db66 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -3057,6 +3057,8 @@ static Property vfio_pci_dev_properties[] = {
>>  DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
>> sub_device_id, PCI_ANY_ID),
>>  DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 0),
>> +DEFINE_PROP_BIT("aer", VFIOPCIDevice, features,
>> +VFIO_FEATURE_ENABLE_AER_BIT, false),
>>  /*
>>   * TODO - support passed fds... is this necessary?
>>   * DEFINE_PROP_STRING("vfiofd", VFIOPCIDevice, vfiofd_name),
> 
> 
> 
> .
> 

-- 
Sincerely,
Cao jin

Re: [Qemu-devel] [PATCH RFC v11 4/4] vfio: add 'aer' property to expose aercap

[Alex Williamson]

On Sat, 31 Dec 2016 17:13:08 +0800
Cao jin  wrote:

> From: Chen Fan 
> 
> Add 'aer' property, let user choose whether expose the aer capability
> or not.

But that's not what it does, it only controls the behavior in response
to non-fatal errors, the capability is exposed regardless.

> Should disable aer feature by default, because only non-fatal
> error is supported now. 

Why does that mean it should be disabled by default?  What bad thing
happens if we enable this opportunistically?

> Signed-off-by: Chen Fan 
> Signed-off-by: Dou Liyang 
> Signed-off-by: Cao jin 
> ---
>  hw/vfio/pci.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 9861f72..fc9db66 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -3057,6 +3057,8 @@ static Property vfio_pci_dev_properties[] = {
>  DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
> sub_device_id, PCI_ANY_ID),
>  DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 0),
> +DEFINE_PROP_BIT("aer", VFIOPCIDevice, features,
> +VFIO_FEATURE_ENABLE_AER_BIT, false),
>  /*
>   * TODO - support passed fds... is this necessary?
>   * DEFINE_PROP_STRING("vfiofd", VFIOPCIDevice, vfiofd_name),

[Qemu-devel] [PATCH RFC v11 4/4] vfio: add 'aer' property to expose aercap

[Cao jin]

From: Chen Fan 

Add 'aer' property, let user choose whether expose the aer capability
or not. Should disable aer feature by default, because only non-fatal
error is supported now.

Signed-off-by: Chen Fan 
Signed-off-by: Dou Liyang 
Signed-off-by: Cao jin 
---
 hw/vfio/pci.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 9861f72..fc9db66 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3057,6 +3057,8 @@ static Property vfio_pci_dev_properties[] = {
 DEFINE_PROP_UINT32("x-pci-sub-device-id", VFIOPCIDevice,
sub_device_id, PCI_ANY_ID),
 DEFINE_PROP_UINT32("x-igd-gms", VFIOPCIDevice, igd_gms, 0),
+DEFINE_PROP_BIT("aer", VFIOPCIDevice, features,
+VFIO_FEATURE_ENABLE_AER_BIT, false),
 /*
  * TODO - support passed fds... is this necessary?
  * DEFINE_PROP_STRING("vfiofd", VFIOPCIDevice, vfiofd_name),
-- 
1.8.3.1