On Fri, 8 Oct 2021 22:31:07 +0200
Eric Farman <farman@xxxxxxxxxxxxx> wrote:
> The Principles of Operations describe the various reasons that
> each individual SIGP orders might be rejected, and the status
> bit that are set for each condition.
>
> For example, for the Set Architecture order, it states:
>
> "If it is not true that all other CPUs in the configu-
> ration are in the stopped or check-stop state, ...
> bit 54 (incorrect state) ... is set to one."
>
> However, it also states:
>
> "... if the CZAM facility is installed, ...
> bit 55 (invalid parameter) ... is set to one."
>
> Since the Configuration-z/Architecture-Architectural Mode (CZAM)
> facility is unconditionally presented, there is no need to examine
> each VCPU to determine if it is started/stopped. It can simply be
> rejected outright with the Invalid Parameter bit.
>
> Fixes: b697e435aeee ("KVM: s390: Support Configuration z/Architecture Mode")
> Signed-off-by: Eric Farman <farman@xxxxxxxxxxxxx>
I like removing and simplifying code while staying architecturally
correct :)
Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> ---
> arch/s390/kvm/sigp.c | 14 +-------------
> 1 file changed, 1 insertion(+), 13 deletions(-)
>
> diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
> index 683036c1c92a..cf4de80bd541 100644
> --- a/arch/s390/kvm/sigp.c
> +++ b/arch/s390/kvm/sigp.c
> @@ -151,22 +151,10 @@ static int __sigp_stop_and_store_status(struct kvm_vcpu *vcpu,
> static int __sigp_set_arch(struct kvm_vcpu *vcpu, u32 parameter,
> u64 *status_reg)
> {
> - unsigned int i;
> - struct kvm_vcpu *v;
> - bool all_stopped = true;
> -
> - kvm_for_each_vcpu(i, v, vcpu->kvm) {
> - if (v == vcpu)
> - continue;
> - if (!is_vcpu_stopped(v))
> - all_stopped = false;
> - }
> -
> *status_reg &= 0xffffffff00000000UL;
>
> /* Reject set arch order, with czam we're always in z/Arch mode. */
> - *status_reg |= (all_stopped ? SIGP_STATUS_INVALID_PARAMETER :
> - SIGP_STATUS_INCORRECT_STATE);
> + *status_reg |= SIGP_STATUS_INVALID_PARAMETER;
> return SIGP_CC_STATUS_STORED;
> }
>
