From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:43297 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728498AbgEEIdb (ORCPT ); Tue, 5 May 2020 04:33:31 -0400 Date: Tue, 5 May 2020 10:33:19 +0200 From: Cornelia Huck Subject: Re: [PATCH] KVM: s390: Remove false WARN_ON_ONCE for the PQAP instruction Message-ID: <20200505103145.1057c2a3.cohuck@redhat.com> In-Reply-To: <480b0bff-8eb5-f75c-a3ce-2555e38917ee@de.ibm.com> References: <20200505073525.2287-1-borntraeger@de.ibm.com> <20200505095332.528254e5.cohuck@redhat.com> <59f1b90c-47d6-2661-0e99-548a53c9bcd6@redhat.com> <480b0bff-8eb5-f75c-a3ce-2555e38917ee@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Christian Borntraeger Cc: David Hildenbrand , Janosch Frank , KVM , linux-s390 , Qian Cai , Pierre Morel , Tony Krowiak On Tue, 5 May 2020 10:27:16 +0200 Christian Borntraeger wrote: > On 05.05.20 10:04, David Hildenbrand wrote: > > On 05.05.20 09:55, Christian Borntraeger wrote: > >> > >> > >> On 05.05.20 09:53, Cornelia Huck wrote: > >>> On Tue, 5 May 2020 09:35:25 +0200 > >>> Christian Borntraeger 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, for example PQAP(QCI). So the WARN_ON_ONCE is not right. Let > >>>> us simply remove it. > >>> > >>> While I agree with removing the WARN_ON_ONCE, I'm wondering why z/VM > >>> gives us intercepts for those fcs... is that just a result of nesting > >>> (or the z/VM implementation), or is there anything we might want to do? > >> > >> Yes nesting. > >> The ECA bit for interpretion is an effective one. So if the ECA bit is off > >> in z/VM (no crypto cards) our ECA bit is basically ignored as these bits > >> are ANDed. > >> I asked Tony to ask the z/VM team if that is the case here. > >> > > > > So we can't detect if we have support for ECA_APIE, because there is no > > explicit feature bit, right? Rings a bell. Still an ugly > > hardware/firmware specification. > > Yes, no matter if this is the case here, we cannot rely on ECA_APIE to not > trigger intercepts. So we must remove the WARN_ON. > > cc stable? Agreed. > > > > > Seems to be the right thing to do > > > > Reviewed-by: David Hildenbrand > > >