[SLOF] [PATCH slof v2] fdt: Pass the resulting device tree to QEMU

[Greg Kurz]

On Tue, 3 Oct 2017 09:22:38 +1100
Alexey Kardashevskiy <aik at ozlabs.ru> wrote:

> On 03/10/17 03:18, Greg Kurz wrote:
> > On Mon,  2 Oct 2017 16:38:19 +1100
> > Alexey Kardashevskiy <aik at ozlabs.ru> wrote:
> >   
> >> This creates flatten device tree and passes it to QEMU via a custom
> >> hypercall right before jumping to RTAS.
> >>
> >> On a machine with 256 CPUs and 256 virtual Intel E1000 devices the blob
> >> is 360KB (356KB structs and 20KB of strings), building such a tree takes
> >> ~2s on a POWER8 box. A simple tree with 1 CPU and a couple of devices
> >> takes 38ms and creates 16KB blob.
> >>
> >> This preloads strings with 40 property names from CPU and PCI device nodes
> >> and the strings lookup only searches within these. Without string reusing
> >> at all, the strings blob is 200KB and rendering time is 1.7sec; with
> >> unlimited reusing, the strings blob is 4KB and rendering time is 2.8sec.
> >>
> >> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> >> ---
> >>
> >> Changes:
> >> v2:
> >> * fixed comments from review
> >> * added strings cache
> >> * changed last_compat_vers from 0x17 to 0x16 as suggested by dwg
> >>  
> > 
> > I wanted to give a try with PHB hotplug and SLOF breaks, because...  
> 
> How does it break exactly? I agree I do not clear the stack but it did not
> show up in any form :-/
> 

Device tree strings 0x0000000004c90000 -> 0x0000000004c90a88
Device tree struct  0x0000000004ca0000 -> 0x0000000004cb0000
+++Q+++ (15990) h_update_dt 1676: DT at 7e43b000 (7e43b000) 19340 bytes
 

( 700 ) Program Exception [ 7dc4b218 ]


    R0 .. R7           R8 .. R15         R16 .. R23         R24 .. R31
000000007dbe2ea8   000000007e463010   0000000000000000   0000000000000006   
000000007e666fe0   000000007dc4b220   0000000000000000   000000007dc05500   
000000007dc0eb00   000000007e711048   000000007e463010   000000007dc090e8   
000000007dc4d000   000000007dbe8510   000000007dc092b8   0000000000000003   
000000007dc5f320   000000007dbe84f0   0000000000008000   000000000000f001   
000000007dc4b218   0000000000000000   000000000000f003   ffffffffffffffff   
000000007e711050   0000000000000000   000000000000f004   000000007dc0ae08   
0000000000000003   0000000000000000   000000000000f005   0000000000000000   

    CR / XER           LR / CTR          SRR0 / SRR1        DAR / DSISR
        80000408   000000007dbe3534   000000007dc0ae08   0000000000000000   
0000000000000000   000000007dc0ae08   8000000000081000           00000000   


45 >  

( 300 ) Data Storage Exception [ 7dc4b240 ]


    R0 .. R7           R8 .. R15         R16 .. R23         R24 .. R31
000000007dbe0308   000000007e463010   0000000000000000   0000000000000006   
000000007e666fe0   4800000824000051   0000000000000000   000000007dc05500   
000000007dc0eb00   000000007dc4b260   000000007e463010   000000007dc090e8   
0000000000000064   000000007dc4eb00   000000007dc092b8   0000000000000003   
0000000000000000   000000007dbe84f0   0000000000008000   000000000000f001   
000000007dc4b240   0000000000000000   000000000000f003   ffffffffffffffff   
000000007dc09f30   0000000000000000   000000000000f004   000000007dbe3ba0   
4800000824000051   0000000000000000   000000000000f005   000000007dc099a8   

    CR / XER           LR / CTR          SRR0 / SRR1        DAR / DSISR
        80000404   000000007dbe3490   000000007dbe42c4   4800000824000051   
0000000020000000   000000007dbe3ba0   8000000000001000           40000000   

I presume that this is the consequence of having 0 on top of the stack
when calling fdt-flatten-tree-free, or am I missing something ?

> 
> > 
> > [...]  
> >> diff --git a/board-qemu/slof/rtas.fs b/board-qemu/slof/rtas.fs
> >> index 54d3929..5beb079 100644
> >> --- a/board-qemu/slof/rtas.fs
> >> +++ b/board-qemu/slof/rtas.fs
> >> @@ -98,6 +98,10 @@ find-qemu-rtas
> >>  ;
> >>  
> >>  : rtas-quiesce ( -- )
> >> +    " /" find-node
> >> +    fdt-flatten-tree
> >> +    dup hv-update-dt  
> > 
> > .. this leaves the hcall return value on the stack. Maybe add:
> > 
> >    ?dup IF
> >       \ Ignore hcall not implemented error, print error otherwise
> >       dup -2 <> IF ." HV-UPDATE-DT error: " . cr ELSE drop THEN
> >    THEN
> >   
> >> +    fdt-flatten-tree-free
> >>      " quiesce" rtas-get-token rtas-cb rtas>token l!
> >>      0 rtas-cb rtas>nargs l!
> >>      0 rtas-cb rtas>nret l!
> >> diff --git a/lib/libhvcall/hvcall.code b/lib/libhvcall/hvcall.code
> >> index 8349748..6ff5715 100644
> >> --- a/lib/libhvcall/hvcall.code
> >> +++ b/lib/libhvcall/hvcall.code
> >> @@ -136,3 +136,8 @@ PRIM(hv_X2d_update_X2d_phandle)
> >>  	uint32_t old_phandle = TOS.u;
> >>  	TOS.u = hv_generic(KVMPPC_H_UPDATE_PHANDLE, old_phandle, new_phandle);
> >>  MIRP
> >> +
> >> +PRIM(hv_X2d_update_X2d_dt)
> >> +	unsigned long dt = TOS.u;
> >> +	TOS.u = hv_generic(KVMPPC_H_UPDATE_DT, dt);
> >> +MIRP
> >> diff --git a/lib/libhvcall/hvcall.in b/lib/libhvcall/hvcall.in
> >> index ab7513a..b59e3f7 100644
> >> --- a/lib/libhvcall/hvcall.in
> >> +++ b/lib/libhvcall/hvcall.in
> >> @@ -32,4 +32,5 @@ cod(hv-logical-memop)
> >>  cod(hv-cas)
> >>  cod(hv-rtas-update)
> >>  cod(hv-update-phandle)
> >> +cod(hv-update-dt)
> >>  cod(get-print-version)  
> >   
> 
>