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

[Iosif Peterfi]

Hello Andreas,

       Try passing amd_iommu=on to the kernel and see how that works.

Regards,
Iosif


On Thu, Aug 21, 2014 at 6:21 PM, Gilberto Nunes <gilberto.nunes32 at gmail.com>
wrote:

>
> 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.
>>
>> Thanks for any hints
>>
>> Andreas
>>
>>
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>>
>
>
>
> --
> Obrigado
>
> Cordialmente
>
> Gilberto Ferreira
>
>
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