Re: [Qemu-devel] [Qemu-ppc] [GIT PULL for qemu-pseries REPOST] pseries: Update SLOF firmware image

[David Gibson]

On Tue, Aug 13, 2019 at 01:00:24PM +0530, Aravinda Prasad wrote:
> 
> 
> On Monday 12 August 2019 03:38 PM, David Gibson wrote:
> > On Mon, Aug 05, 2019 at 02:14:39PM +0530, Aravinda Prasad wrote:
> >> Alexey/David,
> >>
> >> With the SLOF changes, QEMU cannot resize the RTAS blob. Resizing is
> >> required for FWNMI support which extends the RTAS blob to include an
> >> error log upon a machine check.
> >>
> >> The check to valid RTAS buffer fails in the guest because the rtas-size
> >> updated in QEMU is not reflecting in the guest.
> >>
> >> Any workaround for this?
> > 
> > Well, we should still be able to do it, it just means fwnmi would need
> > a SLOF change.  It's an inconvenience, but not really a big deal.
> 
> Yes. Alexey and I were discussing about the following changes to SLOf:
> 
> diff --git a/lib/libhvcall/hvcall.S b/lib/libhvcall/hvcall.S
> index b19f6dbeff2c..880d29a29122 100644
> --- a/lib/libhvcall/hvcall.S
> +++ b/lib/libhvcall/hvcall.S
> @@ -134,6 +134,7 @@ ENTRY(hv_rtas)
>         ori     r3,r3,KVMPPC_H_RTAS@l
>         HVCALL
>         blr
> +    .space 2048
>         .globl hv_rtas_size
>  hv_rtas_size:
>         .long . - hv_rtas;
> 
> 
> But this will statically reserve space for RTAS even when
> SPAPR_CAP_FWNMI_MCE is OFF.

Sure.  We could flag that in the DT somehow, and have SLOF reserve the
space conditionally.

Or we could just ignore it. 2 kiB is miniscule compared to our minimum
guest size, and our current RTAS is microscopic compared to PowerVM.


-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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