[SLOF] [PATCH] vio-vscsi: Support multiple channels / buses

[Alexey Kardashevskiy]

On 10/01/2019 04:05, Thomas Huth wrote:
> The spapr-vscsi device of QEMU supports multiple channels (a.k.a. buses).


What about virtio-scsi?


> But when QEMU is started with a device on a bus > 0, SLOF fails to detect
> the device, so that the boot fails. For example:
> 
>  qemu-system-ppc64 -nodefaults  -nographic -serial stdio -device spapr-vscsi \
>   -blockdev driver=file,filename=/path/to/cdrom.iso,node-name=d1,read-only=on \
>   -device scsi-cd,id=cd1,drive=d1,channel=6,scsi-id=5,lun=1
> 
> Thus SLOF should scan the various channels for bootable SCSI devices, too.
> Since the common SLOF code for scanning SCSI devices has no meaning of
> "channels" or "bus", we simply fake the bus ID to be part of the target
> ID, so instead of supporting 64 targets = 64 devices, we now support
> 8 channel * 64 targets = 512 devices instead.
> 
> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1663160
> Signed-off-by: Thomas Huth <thuth at redhat.com>
> ---
>  board-qemu/slof/vio-vscsi.fs | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/board-qemu/slof/vio-vscsi.fs b/board-qemu/slof/vio-vscsi.fs
> index be11b69..9395148 100644
> --- a/board-qemu/slof/vio-vscsi.fs
> +++ b/board-qemu/slof/vio-vscsi.fs
> @@ -481,14 +481,19 @@ TRUE VALUE first-time-init?
>  \ SCSI scan at boot and child device support
>  \ -----------------------------------------------------------
>  
> -\ We use SRP luns of the form 8000 | (bus << 8) | (id << 5) | lun
> -\ in the top 16 bits of the 64-bit LUN
>  : (set-target)
>      to current-target
>  ;
>  
> -: dev-generate-srplun ( target lun -- )
> -    swap 8 << 8000 or or 30 <<
> +\ We use SRP luns of the form 8000 | (target << 8) | (bus << 5) | lun
> +\ in the top 16 bits of the 64-bit LUN (i.e. the "Logical unit addressing
> +\ method" in SAM5). Since the generic scsi-probe code of SLOF does not
> +\ really care about buses, we assume that the upper 3 bits of the "target"
> +\ value are the "bus" field.
> +: dev-generate-srplun ( bus+target lun -- srplun )
> +    swap dup 1 >> e0 and      ( lun bus+target bus )
> +    swap 3f and 8 <<          ( lun bus target )
> +    8000 or or or 30 <<
>  ;
>  
>  \ We obtain here a unit address on the stack, since our #address-cells
> @@ -508,8 +513,9 @@ TRUE VALUE first-time-init?
>  ;
>  
>  \ Report the amount of supported SCSI IDs - QEMU uses "max_target = 63"
> +\ and "max_channel = 7", we combine both to 64 * 8 = 512 devices
>  : dev-max-target ( -- #max-target )
> -    40
> +    200
>  ;
>  
>  " scsi-probe-helpers.fs" included
> 

-- 
Alexey