From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre Morel Subject: Re: [PATCH v3 3/3] KVM: s390: vsie: Make use of CRYCB FORMAT2 clear Date: Thu, 23 Aug 2018 13:47:11 +0200 Message-ID: References: <1535019956-23539-1-git-send-email-pmorel@linux.ibm.com> <1535019956-23539-4-git-send-email-pmorel@linux.ibm.com> <912d013c-c925-fb3e-ed1d-2d778a60c189@linux.ibm.com> <58427761-072c-e420-a881-4decbe9088bb@linux.ibm.com> Reply-To: pmorel@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: linux-kernel@vger.kernel.org, cohuck@redhat.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org, akrowiak@linux.ibm.com, borntraeger@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com To: Janosch Frank , David Hildenbrand Return-path: In-Reply-To: <58427761-072c-e420-a881-4decbe9088bb@linux.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 23/08/2018 13:33, Janosch Frank wrote: > On 8/23/18 1:21 PM, David Hildenbrand wrote: >> On 23.08.2018 13:05, Janosch Frank wrote: >>> On 8/23/18 12:25 PM, Pierre Morel wrote: >>>> The comment preceding the shadow_crycb function is >>>> misleading, we effectively accept FORMAT2 CRYCB in the >>>> guest. >>> >>> I beg to differ: >>> >>> if (!(crycbd_o & vcpu->arch.sie_block->crycbd & CRYCB_FORMAT1)) >>> return 0; >> >> FORMAT2 includes bit FORMAT1 (backwards compatible) > > Right, this check is very misleading because of the constant, we > effectively test against Format 0 and Format 2. > > Can we make this clearer by explicitly ANDing 0x01 or adding a comment? yes, done, I modified the comment in front of the function. > > Code makes sense: > Reviewed-by: Janosch Frank Thanks, regards, Pierre > >> >>> >>>> >>>> When using FORMAT2 in the host we do not need to or with >>>> FORMAT1. >>>> >>>> Signed-off-by: Pierre Morel >>>> --- >>>> arch/s390/kvm/vsie.c | 6 +++--- >>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c >>>> index 38ea5da..e0e6fbf 100644 >>>> --- a/arch/s390/kvm/vsie.c >>>> +++ b/arch/s390/kvm/vsie.c >>>> @@ -140,7 +140,8 @@ static int prepare_cpuflags(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) >>>> * Create a shadow copy of the crycb block and setup key wrapping, if >>>> * requested for guest 3 and enabled for guest 2. >>>> * >>>> - * We only accept format-1 (no AP in g2), but convert it into format-2 >>>> + * We accept format-1 or format-2, but we treat it as a format-1 (no AP in g2), >>>> + * and we convert it into format-2 in the shadow CRYCB. >>>> * There is nothing to do for format-0. >>>> * >>>> * Returns: - 0 if shadowed or nothing to do >>>> @@ -179,8 +180,7 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) >>>> return set_validity_icpt(scb_s, 0x0035U); >>>> >>>> scb_s->ecb3 |= ecb3_flags; >>>> - scb_s->crycbd = ((__u32)(__u64) &vsie_page->crycb) | CRYCB_FORMAT1 | >>>> - CRYCB_FORMAT2; >>>> + scb_s->crycbd = ((__u32)(__u64) &vsie_page->crycb) | CRYCB_FORMAT2; >>> >>> That's purely cosmetic but valid. >>> >>>> >>>> /* xor both blocks in one run */ >>>> b1 = (unsigned long *) vsie_page->crycb.dea_wrapping_key_mask; >> >> Reviewed-by: David Hildenbrand >> > > -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany