Re: [Qemu-discuss] Best Intel hardware for qemu

[Lars Bonnesen]

Yes, I get it, thanks. Any way to find out if a given hardware supports
VFIO?

regards, Lars

On Wed, Apr 10, 2019, 20:56 Jakob Bohm <address@hidden> wrote:

> As I wrote, qemu can pass disks (and disk partitions) through without
> passing the disk controller through.  To qemu, a physical disk is just
> another virtual disk storage format.
>
> But if you want to pass through an entire PCI disk controller (with all
> its disks) for faster I/O, then VFIO is needed.
>
> On 10/04/2019 20:40, Lars Bonnesen wrote:
> > I want to pass local disks to a VM in order to run freenas or similar.
> >
> > Regards, Lars.
> >
> > On Wed, Apr 10, 2019, 20:20 Jakob Bohm <address@hidden
> > <mailto:address@hidden>> wrote:
> >
> >     If you pass through the disk access to your SAN partitions as disk
> >     accesses to block devices (such as SAN client drivers) in the host
> >     machine, you don't need VFIO for that.  This can handle nearly
> >     unlimited number of virtual machines without running out of PCI
> >     slots in the host machine.  This is the equivalent of "passing
> >     through a SAN disk" in VMWare, but isn't artificially limited to
> >     SAN disks (for example, you can layer the Linux multipath drivers
> >     and/or the Linux disk encryption drivers between the virtual
> >     machine and the actual SAN).
> >
> >     If you pass through the network access to your (iSCSI or NBD) SAN
> >     as network traffic via the general qemu/kvm network features, you
> >     don't need VFIO for that.  This can handle nearly unlimited number
> >     of virtual machines without running out of PCI slots in the host
> >     machine.  This is equivalent to using a "VMWare virtual switch".
> >
> >     If you dedicate a physical SAN adapter (iSCSI, NBD, SAS or fibre
> >     channel) to each virtual machine and pass it through to that
> >     virtual machine, you need VFIO for that.  As on VMWare, this will
> >     limit you to one virtual machine for each PCI slot in the
> >     motherboard.
> >
> >     If you dedicate a physical network adapter (NIC) to each individual
> >     virtual machine and pass it through to PCI drivers in that virtual
> >     machine, you need VFIO for that.  This too will limit you to one
> >     virtual machine for each PCI slot in the motherboard.
> >
> >     As for passing through raw SCSI devices or busses, I don't know
> >     if the latest qemu versions have the ability to do this at a
> >     hardware-independent level like VMWare does (VM sends standard
> >     SCSI requests to qemu virtual SCSI adapter, qemu sends those
> >     same SCSI requests to real SCSI hardware via something like the
> >     Linux "SCSI generic" driver, optionally mapping at most the
> >     SCSI-level bus address).
> >
> >     On 10/04/2019 19:42, Lars Bonnesen wrote:
> >      > But for sure I want passthru - for running virtualized SAN and
> such
> >      >
> >      > Any unofficial list?
> >      >
> >      > Regards, Lars.
> >      >
> >      > On Wed, Apr 10, 2019, 18:58 Friedrich Oslage
> >     <address@hidden <mailto:
> address@hidden>>
> >      > wrote:
> >      >
> >      >> As long as it's VT-x capable and can run Linux, you're good to
> go.
> >      >>
> >      >> It only gets tricky once you start using VFIO (direct
> passthrough of
> >      >> host PCI devices to a VM, such as GPUs, NICs or NVMes for
> >     instance). You
> >      >> need VT-d support for that and both the CPU and mainboard have to
> >      >> support it. And not only do they have to support it, they have to
> >      >> support in a usable way with decent iommu group isolation and
> >     without
> >      >> weird bugs. There are no (official) compatibility lists for
> >     this, it's
> >      >> still mostly trial and error...
> >      >>
> >      >> Regards
> >      >> Friedrich
> >      >>
> >      >> On 4/10/19 2:26 PM, Lars Bonnesen wrote:
> >      >>> So I am coming from the VMware world (with comprehensive
> >     compatibillity
> >      >>> lists) but about to start a project with KVM/Qemu and I would
> >     like to
> >      >> setup
> >      >>> an inexpensive test setup for this purpose.
> >      >>>
> >      >>> I am thinking of buying one of SuperMicros IoT-servers like
> >      >>>
> >      >>
> >
> https://www.supermicro.com/products/system/Mini-ITX/SYS-E300-9D-4CN8TP.cfm
> >      >>> Will this be a nice pick for Qemu? Or any VT-supportet system
> >     will work
> >      >>> fine?
> >      >>>
> >      >>> Regards, Lars.
> >
>
>
> Enjoy
>
> Jakob
> --
> Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
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