[Qemu-devel] How to modify QEMU source to read the bus for SATA directly?

[Qemu-devel] How to modify QEMU source to read the bus for SATA directly?

[Peter Teoh]

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My objective is not to emulate the SATA disk in anyway, but to passthrough
all command the guest OS (either Windows or Linux) issued directly to the
underlying harddisk.

Will the following parameters achieved that goal?

./x86_64-softmmu/qemu-system-x86_64 \
    -drive file=...,if=none,id=mydisk \
    -device ich9-ahci,id=ahci \
    -device ide-drive,drive=mydisk,bus=ahci.0

In one PC (Intel-based) I found the "ich9-ahci" in the hardware description
output (using "lshw").

But in another PC (AMD-based) the "lshw" output is as follows:

        *-storage
             description: SATA controller
             product: FCH SATA Controller [AHCI mode]
             vendor: Advanced Micro Devices, Inc. [AMD]
             physical id: 11
             bus info: pci@0000:00:11.0
             version: 40
             width: 32 bits
             clock: 66MHz
             capabilities: storage msi ahci_1.0 bus_master cap_list
             configuration: driver=ahci latency=32
             resources: irq:83 ioport:f140(size=8) ioport:f130(size=4)
ioport:f120(size=8) ioport:f110(size=4) ioport:f100(size=16)
memory:feb70000-feb707ff

Now my question is:   Is it possible to modify the QEMU source code, or
pass in the correct parameters in the command line, so as provide direct
I/O access from the QEMU guest all the way to the underlying host's AHCI
sata bus (based on my AMD's hardware configuration as above)?


-- 
Regards,
Peter Teoh

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Re: [Qemu-devel] How to modify QEMU source to read the bus for SATA directly?

[Paolo Bonzini]

On 16/04/2015 15:25, Peter Teoh wrote:
> 
> Now my question is:   Is it possible to modify the QEMU source code, or
> pass in the correct parameters in the command line, so as provide direct
> I/O access from the QEMU guest all the way to the underlying host's AHCI
> sata bus (based on my AMD's hardware configuration as above)?

You can use PCI passthrough and let the guest use the whole SATA bus, if
you have another way to access other disks on the same bus (e.g. boot
from a USB stick or access the filesystems on NFS).

Or you can use SCSI passthrough and pass the /dev/sdX device to the
guest, e.g.

    -device virtio-scsi-pci
    -drive if=none,file=/dev/sdb,id=sdb,cache=none,format=raw
    -device scsi-block,drive=sdb

The guest then will talk to the host's ATA->SCSI translation layer, and
will be able to send raw ATA commands via the ATA PASSTHROUGH command.

Paolo

Re: [Qemu-devel] How to modify QEMU source to read the bus for SATA directly?

[Peter Teoh]

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On Thu, Apr 16, 2015 at 9:43 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:

>
>
> On 16/04/2015 15:25, Peter Teoh wrote:
> >
> > Now my question is:   Is it possible to modify the QEMU source code, or
> > pass in the correct parameters in the command line, so as provide direct
> > I/O access from the QEMU guest all the way to the underlying host's AHCI
> > sata bus (based on my AMD's hardware configuration as above)?
>
> You can use PCI passthrough and let the guest use the whole SATA bus, if
> you have another way to access other disks on the same bus (e.g. boot
> from a USB stick or access the filesystems on NFS).
>
> Or you can use SCSI passthrough and pass the /dev/sdX device to the
> guest, e.g.
>
>     -device virtio-scsi-pci
>     -drive if=none,file=/dev/sdb,id=sdb,cache=none,format=raw
>     -device scsi-block,drive=sdb
>
> The guest then will talk to the host's ATA->SCSI translation layer, and
> will be able to send raw ATA commands via the ATA PASSTHROUGH command.
>
> Paolo
>

Thank you very much, that answer saved me many hours of search/trial and
errors.   And seems to work for now...need more testing.

Thanks again Paolo :-).


-- 
Regards,
Peter Teoh

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Re: [Qemu-devel] How to modify QEMU source to read the bus for SATA directly?

[Paolo Bonzini]

On 16/04/2015 16:26, Peter Teoh wrote:
> 
>     You can use PCI passthrough and let the guest use the whole SATA bus, if
>     you have another way to access other disks on the same bus (e.g. boot
>     from a USB stick or access the filesystems on NFS).
> 
>     Or you can use SCSI passthrough and pass the /dev/sdX device to the
>     guest, e.g.
> 
>         -device virtio-scsi-pci
>         -drive if=none,file=/dev/sdb,id=sdb,cache=none,format=raw
>         -device scsi-block,drive=sdb
> 
>     The guest then will talk to the host's ATA->SCSI translation layer, and
>     will be able to send raw ATA commands via the ATA PASSTHROUGH command.
> 
> Thank you very much, that answer saved me many hours of search/trial and
> errors.   And seems to work for now...need more testing.

FWIW, which one did you use and what kind of command did you need?

Paolo