Re: No IOMMU/DMAR with DELL 3020

From: Konstantin Belousov <kostikbel_at_gmail.com>
Date: Thu, 9 Apr 2015 13:03:35 +0300
On Thu, Apr 09, 2015 at 11:52:33AM +0300, Slawa Olhovchenkov wrote:
> On Thu, Apr 09, 2015 at 11:35:12AM +0300, Konstantin Belousov wrote:
> 
> > On Thu, Apr 09, 2015 at 10:28:10AM +0200, Gustau P?rez wrote:
> > >    Yup, sorry for the error. I checked the micro in the ark and it has vt-d:
> > > 
> > >               http://goo.gl/CZZRHz
> > It only indicates that the CPU/northbridge has the hardware, but BIOS must
> > do a work to configure it and to inform the OS about the configuration.
> > Your BIOS did not.
> >  
> > > 
> > >    in the bios, there's only one option to enable virtualization
> > > support, which is ticked.
> > > 
> > >    The complete log is here:
> > > 
> > >              http://dpaste.com/28FDMJQ
> > > 
> > Dmesg would not give you any useful information there. A DMAR table
> > is either present, or is it not. In the later case, OS cannot use the
> > hardware, and if no option in BIOS is present, your only choice is to
> > complain to the machine/BIOS vendor.
> 
> May be some OS utilites can do same work?
> This is theoretically capable?

No, OS must know the peculiarities of the particular chipset.  But also,
it must know the intimate details of the BIOS operation, since several
facilities perform background DMA transfers not under the OS control.
Examples are USB legacy emulation, BMC working with the main memory,
or UMA GPU in BIOS-configured mode.  Normally, BIOS communicates the
requirements of such facilities to OS using RMRR records in the DMAR
table.
Received on Thu Apr 09 2015 - 08:03:44 UTC

This archive was generated by hypermail 2.4.0 : Wed May 19 2021 - 11:40:56 UTC