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SubjectRe: [PATCH v3 3/3] KVM: s390: vsie: Make use of CRYCB FORMAT2 clear
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On 23/08/2018 13:21, 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)
>
>>
>>>
>>> When using FORMAT2 in the host we do not need to or with
>>> FORMAT1.
>>>
>>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>>> ---
>>> 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 <david@redhat.com>
>

Thanks,

regards,
Pierre


--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany

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