Hardware support for vt-posted interrupts described in vt-directed-io-spec for assigned devices

Hardware support for vt-posted interrupts described in vt-directed-io-spec for assigned devices

[bk rakesh]

Hello,

I am using the S2600CP server board with cpu "Intel(R) Xeon(R) CPU
E5-2620 v2 @ 2.10GHz" which supports for APICv,

Does this hardware support the vt-d posted interrupt feature as  described in
"[v3 00/26] Add VT-d Posted-Interrupts support" and
https://lkml.org/lkml/2014 /12/3/102 ,

Requesting to get any information about the hardware that supports this feature.

Thanks,
Rakesh

Re: Hardware support for vt-posted interrupts described in vt-directed-io-spec for assigned devices

[bk rakesh]

Adding few more information regarding the setup which i had created to
test the vt-d posted interrupts for assigned devices,

Hardware used for evaluating vt-posted interrupts
    cpu "E5-2620 v2 @ 2.10GHz" and "S2600CP server board"

I had used kernel-3.18 patched with "KVM-VFIO IRQ forward
control(posted by eric.auger@linaro.org)", "hierarchy irqdomian(posted
by jiang.liu@linux.intel.com)" and "VT-d Posted-Interrupts
support(http://lwn.net/Articles/626050/) and assigned the ixgbe 10G
NIC via vfio passthrough using qemu-kvm, But resulted in the following
dmesg output,

[233783.657187] dmar: DRHD: handling fault status reg 602
[233783.662926] dmar: INTR-REMAP: Request device [[02:00.0] fault index 47
INTR-REMAP:[fault reason 36] Detected reserved fields in the IRTE entry

I had checked the hardware supported for posted interrupt capability
via capability register bit 59 (#define cap_pi_support(c)    (((c) >>
59) & 1)),  as described in
"http://www.intel.com/content/www/us/en/embedded/technology/virtualization/vt-directed-io-spec.html",
Which resulted as not supported, Can anyone suggest that does this hw
support posted vt-d feature ? if not then which one to use.

Thanks


On Fri, Mar 20, 2015 at 12:49 PM, bk rakesh <rakeshbkrish@gmail.com> wrote:
>
> Hello,
>
> I am using the S2600CP server board with cpu "Intel(R) Xeon(R) CPU
> E5-2620 v2 @ 2.10GHz" which supports for APICv,
>
> Does this hardware support the vt-d posted interrupt feature as  described in
> "[v3 00/26] Add VT-d Posted-Interrupts support" and
> https://lkml.org/lkml/2014 /12/3/102 ,
>
> Requesting to get any information about the hardware that supports this feature.
>
> Thanks,
> Rakesh

Re: Hardware support for vt-posted interrupts described in vt-directed-io-spec for assigned devices

[Alex Williamson]

On Fri, 2015-03-20 at 15:24 +0530, bk rakesh wrote:
> Adding few more information regarding the setup which i had created to
> test the vt-d posted interrupts for assigned devices,
> 
> Hardware used for evaluating vt-posted interrupts
>     cpu "E5-2620 v2 @ 2.10GHz" and "S2600CP server board"
> 
> I had used kernel-3.18 patched with "KVM-VFIO IRQ forward
> control(posted by eric.auger@linaro.org)",

IRQ forwarding in an ARM technology for handling level triggered
interrupts, not Intel, not even x86.

>  "hierarchy irqdomian(posted
> by jiang.liu@linux.intel.com)" and "VT-d Posted-Interrupts
> support(http://lwn.net/Articles/626050/) and assigned the ixgbe 10G
> NIC via vfio passthrough using qemu-kvm, But resulted in the following
> dmesg output,
> 
> [233783.657187] dmar: DRHD: handling fault status reg 602
> [233783.662926] dmar: INTR-REMAP: Request device [[02:00.0] fault index 47
> INTR-REMAP:[fault reason 36] Detected reserved fields in the IRTE entry

This suggests bugs in the patch series for setting bits that are
reserved on the hardware in your test system.

> I had checked the hardware supported for posted interrupt capability
> via capability register bit 59 (#define cap_pi_support(c)    (((c) >>
> 59) & 1)),  as described in
> "http://www.intel.com/content/www/us/en/embedded/technology/virtualization/vt-directed-io-spec.html",
> Which resulted as not supported, Can anyone suggest that does this hw
> support posted vt-d feature ?

Your own hardware is telling you that it doesn't support it.

>  if not then which one to use.

Personally I would have no expectation that any currently shipping
hardware supports this feature.  If you watch one of GregKH's talks on
how the Linux community works or follow development for a while, you'll
see and hear that Intel will often pre-enable features before the
hardware that supports it is available.  I suspect this is one of those
features.  Thanks,

Alex

Re: Hardware support for vt-posted interrupts described in vt-directed-io-spec for assigned devices

[Eric Auger]

On 03/20/2015 03:04 PM, Alex Williamson wrote:
> On Fri, 2015-03-20 at 15:24 +0530, bk rakesh wrote:
>> Adding few more information regarding the setup which i had created to
>> test the vt-d posted interrupts for assigned devices,
>>
>> Hardware used for evaluating vt-posted interrupts
>>     cpu "E5-2620 v2 @ 2.10GHz" and "S2600CP server board"
>>
>> I had used kernel-3.18 patched with "KVM-VFIO IRQ forward
>> control(posted by eric.auger@linaro.org)",
> 
> IRQ forwarding in an ARM technology for handling level triggered
> interrupts, not Intel, not even x86.

Hi Alex,

Feng's series relies on few pacth files in "KVM-VFIO IRQ forward
control", basically for KVM_DEV_VFIO_DEVICE group introduction in
KVM-VFIO. This explains why you find some references to that patch here
I guess.

Best Regards

Eric

> 
>>  "hierarchy irqdomian(posted
>> by jiang.liu@linux.intel.com)" and "VT-d Posted-Interrupts
>> support(http://lwn.net/Articles/626050/) and assigned the ixgbe 10G
>> NIC via vfio passthrough using qemu-kvm, But resulted in the following
>> dmesg output,
>>
>> [233783.657187] dmar: DRHD: handling fault status reg 602
>> [233783.662926] dmar: INTR-REMAP: Request device [[02:00.0] fault index 47
>> INTR-REMAP:[fault reason 36] Detected reserved fields in the IRTE entry
> 
> This suggests bugs in the patch series for setting bits that are
> reserved on the hardware in your test system.
> 
>> I had checked the hardware supported for posted interrupt capability
>> via capability register bit 59 (#define cap_pi_support(c)    (((c) >>
>> 59) & 1)),  as described in
>> "http://www.intel.com/content/www/us/en/embedded/technology/virtualization/vt-directed-io-spec.html",
>> Which resulted as not supported, Can anyone suggest that does this hw
>> support posted vt-d feature ?
> 
> Your own hardware is telling you that it doesn't support it.
> 
>>  if not then which one to use.
> 
> Personally I would have no expectation that any currently shipping
> hardware supports this feature.  If you watch one of GregKH's talks on
> how the Linux community works or follow development for a while, you'll
> see and hear that Intel will often pre-enable features before the
> hardware that supports it is available.  I suspect this is one of those
> features.  Thanks,
> 
> Alex
> 
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Re: Hardware support for vt-posted interrupts described in vt-directed-io-spec for assigned devices

[Alex Williamson]

On Fri, 2015-03-20 at 15:10 +0100, Eric Auger wrote:
> On 03/20/2015 03:04 PM, Alex Williamson wrote:
> > On Fri, 2015-03-20 at 15:24 +0530, bk rakesh wrote:
> >> Adding few more information regarding the setup which i had created to
> >> test the vt-d posted interrupts for assigned devices,
> >>
> >> Hardware used for evaluating vt-posted interrupts
> >>     cpu "E5-2620 v2 @ 2.10GHz" and "S2600CP server board"
> >>
> >> I had used kernel-3.18 patched with "KVM-VFIO IRQ forward
> >> control(posted by eric.auger@linaro.org)",
> > 
> > IRQ forwarding in an ARM technology for handling level triggered
> > interrupts, not Intel, not even x86.
> 
> Hi Alex,
> 
> Feng's series relies on few pacth files in "KVM-VFIO IRQ forward
> control", basically for KVM_DEV_VFIO_DEVICE group introduction in
> KVM-VFIO. This explains why you find some references to that patch here
> I guess.

Ah yes, makes sense.  Thanks,

Alex