Re: [PATCH 1/3] KVM: PPC: Book3S HV: Stop returning internal values to userspace

[Nicholas Piggin <npiggin@gmail.com>]

Excerpts from Fabiano Rosas's message of December 24, 2021 7:15 am:
> Our kvm_arch_vcpu_ioctl_run currently returns the RESUME_HOST values
> to userspace, against the API of the KVM_RUN ioctl which returns 0 on
> success.
> 
> Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
> ---
> This was noticed while enabling the kvm selftests for powerpc. There's
> an assert at the _vcpu_run function when we return a value different
> from the expected.

That's nasty. Looks like qemu never touches the return value except if
it was < 0, so hopefully should be okay.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> ---
>  arch/powerpc/kvm/powerpc.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index a72920f4f221..1e130bb087c4 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -1849,6 +1849,14 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>  #ifdef CONFIG_ALTIVEC
>  out:
>  #endif
> +
> +	/*
> +	 * We're already returning to userspace, don't pass the
> +	 * RESUME_HOST flags along.
> +	 */
> +	if (r > 0)
> +		r = 0;
> +
>  	vcpu_put(vcpu);
>  	return r;
>  }
> -- 
> 2.33.1
> 
>