Re: [PATCH] spapr: Handle HPT allocation failure in nested guest

[David Gibson]

On Fri, Sep 11, 2020 at 01:31:23AM -0300, Fabiano Rosas wrote:
> The nested KVM code does not yet support HPT guests. Calling the
> KVM_CAP_PPC_ALLOC_HTAB ioctl currently leads to KVM setting the guest
> as HPT and erroneously executing code in L1 that should only run in
> hypervisor mode, leading to an exception in the L1 vcpu thread when it
> enters the nested guest.
> 
> This can be reproduced with -machine max-cpu-compat=power8 in the L2
> guest command line.
> 
> The KVM code has since been modified to fail the ioctl when running in
> a nested environment so QEMU needs to be able to handle that. This
> patch provides an error message informing the user about the lack of
> support for HPT in nested guests.
> 
> Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>

Applied to ppc-for-5.2.

> ---
>  hw/ppc/spapr.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 9bce1892b5..ea2c755310 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1483,6 +1483,12 @@ void spapr_reallocate_hpt(SpaprMachineState *spapr, 
> int shift,
>      spapr_free_hpt(spapr);
>  
>      rc = kvmppc_reset_htab(shift);
> +
> +    if (rc == -EOPNOTSUPP) {
> +        error_setg(errp, "HPT not supported in nested guests");
> +        return;
> +    }
> +
>      if (rc < 0) {
>          /* kernel-side HPT needed, but couldn't allocate one */
>          error_setg_errno(errp, errno,

-- 
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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