From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AF506C33C9E for ; Thu, 30 Jan 2020 10:39:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 801B720658 for ; Thu, 30 Jan 2020 10:39:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WAek6Iyw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726947AbgA3Kjy (ORCPT ); Thu, 30 Jan 2020 05:39:54 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:31934 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726893AbgA3Kjy (ORCPT ); Thu, 30 Jan 2020 05:39:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580380793; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zUvMSNl99Jwy3aPQU5yVQFcXIlRXEbblcUjGKucu2hE=; b=WAek6IywAAOUyykcUL4JfiCzm2n9poS39wmcO5GOpWAi75OPnzi0tNNn0NYkwgM18DjQPU ElFN+t5c3iJEmpZjCo8Xf6FDZCWrgQFcQjuZVnQaqMXANuWNV02xlrzqnkgQK1AJoDUeld DSfUupIzcAyc/ZTu1sJ9XOMLXhqcIVo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-214-H9m9G7F1Ok6g0BZICdkEUg-1; Thu, 30 Jan 2020 05:39:49 -0500 X-MC-Unique: H9m9G7F1Ok6g0BZICdkEUg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1EFDD8017CC; Thu, 30 Jan 2020 10:39:48 +0000 (UTC) Received: from gondolin (ovpn-117-199.ams2.redhat.com [10.36.117.199]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8CEFE1001B07; Thu, 30 Jan 2020 10:39:43 +0000 (UTC) Date: Thu, 30 Jan 2020 11:39:41 +0100 From: Cornelia Huck To: David Hildenbrand Cc: Christian Borntraeger , frankja@linux.ibm.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, thuth@redhat.com, stable@kernel.org Subject: Re: [PATCH/FIXUP FOR STABLE BEFORE THIS SERIES] KVM: s390: do not clobber user space fpc during guest reset Message-ID: <20200130113941.78e4bf2e.cohuck@redhat.com> In-Reply-To: <7b40856d-8153-ad3f-bea8-110fa6e1aea6@redhat.com> References: <20200129200312.3200-2-frankja@linux.ibm.com> <1580374500-31247-1-git-send-email-borntraeger@de.ibm.com> <7b40856d-8153-ad3f-bea8-110fa6e1aea6@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 30 Jan 2020 10:49:35 +0100 David Hildenbrand wrote: > On 30.01.20 09:55, Christian Borntraeger wrote: > > The initial CPU reset currently clobbers the userspace fpc. This was an > > oversight during a fixup for the lazy fpu reloading rework. The reset > > calls are only done from userspace ioctls. No CPU context is loaded, so > > we can (and must) act directly on the sync regs, not on the thread > > context. Otherwise the fpu restore call will restore the zeroes fpc to > > userspace. > > > > Cc: stable@kernel.org > > Fixes: 9abc2a08a7d6 ("KVM: s390: fix memory overwrites when vx is disabled") > > Signed-off-by: Christian Borntraeger > > --- > > arch/s390/kvm/kvm-s390.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > > index c059b86..eb789cd 100644 > > --- a/arch/s390/kvm/kvm-s390.c > > +++ b/arch/s390/kvm/kvm-s390.c > > @@ -2824,8 +2824,7 @@ static void kvm_s390_vcpu_initial_reset(struct kvm_vcpu *vcpu) > > vcpu->arch.sie_block->gcr[14] = CR14_UNUSED_32 | > > CR14_UNUSED_33 | > > CR14_EXTERNAL_DAMAGE_SUBMASK; > > - /* make sure the new fpc will be lazily loaded */ > > - save_fpu_regs(); > > + vcpu->run->s.regs.fpc = 0; > > current->thread.fpu.fpc = 0; > > vcpu->arch.sie_block->gbea = 1; > > vcpu->arch.sie_block->pp = 0; > > > > kvm_arch_vcpu_ioctl() does a vcpu_load(vcpu), followed by the call to > kvm_arch_vcpu_ioctl_initial_reset(), followed by a vcpu_put(). > > What am I missing? I have been staring at this patch for some time now, and I fear I'm missing something as well. Can we please get more explanation? > > (we could get rid of the kvm_arch_vcpu_ioctl_initial_reset() wrapper) >