[PVE-User] IOMMU and AMD-Vi useful/recommended for Proxmox ?

[Iosif Peterfi]

On Thu, Aug 21, 2014 at 6:43 PM, <lst_hoe02 at kwsoft.de> wrote:

>
> Zitat von Gilberto Nunes <gilberto.nunes32 at gmail.com>:
>
>
>  http://en.wikipedia.org/wiki/X86_virtualization#I.2FO_MMU_
>> virtualization_.28AMD-Vi_and_VT-d.29
>>
>> 2014-08-21 13:06 GMT-03:00 <lst_hoe02 at kwsoft.de>:
>>
>>  Hello,
>>>
>>> when inspecting the "dmesg" output on one of the PVE servers i got the
>>> follwoing:
>>>
>>> No AGP bridge found
>>> Node 0: aperture @ 0 size 32 MB
>>> Your BIOS doesn't leave a aperture memory hole
>>> Please enable the IOMMU option in the BIOS setup
>>> This costs you 64 MB of RAM
>>> Mapping aperture over 65536 KB of RAM @ 20000000
>>> PM: Registered nosave memory: 0000000020000000 - 0000000024000000
>>> AMD-Vi disabled by default: pass amd_iommu=on to enable
>>>
>>> My first action was to go to the BIOS (the machine is still test) and
>>> activated the IOMMU. The message stays the same. Next try was to set
>>> iommu=noaperture as boot parameter because it was suggested for machine
>>> having IOMMU but no AGP anymore. This lead to
>>>
>>> PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
>>> Placing 64MB software IO TLB between ffff880020000000 - ffff880024000000
>>> software IO TLB at phys 0x20000000 - 0x24000000
>>>
>>> Which looks like the IOMMU emulated in software...
>>>
>>> This lead to the question what the real benefits of AMD-Vi / IOMMU are
>>> for
>>> Proxmox/KVM if they are disabled by default and can not be enabled
>>> straight
>>> forward as it looks like?
>>>
>>> The Board in question is a ASUS KCMA-D8, BIOS 3102 with two AMD Opteron
>>> 4226 CPUs.
>>>
>>>
> Hm, yes. But this still lead to the question which boot parameter should
> be used if any:
>
> iommu=noaperture which looks like deaktivating GART IOMMU but also
> hardware IOMMU at all
> amd_iommu which should activate AMD-Vi which includes IOMMU
> no parameter which looks like using GART IOMMU but not AMD-Vi and only
> when IOMMU is enabled in BIOS
>
> or do i simply not need it at all if no passthrough of devices is required?
>
> me->confused
>
> Thanks
>
>
> Andreas
>
>
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Hello,

>From the original post I thought you were trying to activate AMD-Vi. What
are you trying to accomplish ?

Regards,
Iosif
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