On Tue, 5 May 2020 10:35:15 +0200
Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote:
> In LPAR we will only get an intercept for FC==3 for the PQAP
> instruction. Running nested under z/VM can result in other intercepts as
> well as ECA_APIE is an effective bit: If one hypervisor layer has
> turned this bit off, the end result will be that we will get intercepts for
> all function codes. Usually the first one will be a query like PQAP(QCI).
> So the WARN_ON_ONCE is not right. Let us simply remove it.
Thanks, that is helpful to describe.
Fixes: e5282de93105 ("s390: ap: kvm: add PQAP interception for AQIC")
> Cc: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> Cc: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Link: https://lore.kernel.org/kvm/20200505073525.2287-1-borntraeger@xxxxxxxxxx
This links to v1, which is probably not what you want :)
> Reported-by: Qian Cai <cailca@xxxxxxxxxx>
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
> ---
> arch/s390/kvm/priv.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 69a824f9ef0b..893893642415 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -626,10 +626,12 @@ static int handle_pqap(struct kvm_vcpu *vcpu)
> * available for the guest are AQIC and TAPQ with the t bit set
> * since we do not set IC.3 (FIII) we currently will only intercept
> * the AQIC function code.
> + * Note: running nested under z/VM can result in intercepts for other
> + * function codes, e.g. PQAP(QCI). We do not support this and bail out.
> */
> reg0 = vcpu->run->s.regs.gprs[0];
> fc = (reg0 >> 24) & 0xff;
> - if (WARN_ON_ONCE(fc != 0x03))
> + if (fc != 0x03)
> return -EOPNOTSUPP;
>
> /* PQAP instruction is allowed for guest kernel only */
