From: Cornelia Huck <cohuck@redhat.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>,
Janis Schoetterl-Glausch <scgl@linux.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
"open list:KERNEL VIRTUAL MACHINE for s390 (KVM/s390)"
<kvm@vger.kernel.org>,
"open list:S390" <linux-s390@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] KVM: s390: Enable specification exception interpretation
Date: Wed, 07 Jul 2021 10:54:02 +0200 [thread overview]
Message-ID: <87lf6ifqs5.fsf@redhat.com> (raw)
In-Reply-To: <05430c91-6a84-0fc9-0af4-89f408eb691f@de.ibm.com>
On Wed, Jul 07 2021, Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> On 06.07.21 13:47, Janis Schoetterl-Glausch wrote:
>> When this feature is enabled the hardware is free to interpret
>> specification exceptions generated by the guest, instead of causing
>> program interruption interceptions.
>>
>> This benefits (test) programs that generate a lot of specification
>> exceptions (roughly 4x increase in exceptions/sec).
>>
>> Interceptions will occur as before if ICTL_PINT is set,
>> i.e. if guest debug is enabled.
>
> I think I will add
>
> There is no indication if this feature is available or not and the hardware
> is free to interpret or not. So we can simply set this bit and if the
> hardware ignores it we fall back to intercept 8 handling.
Sounds good.
>
>
> With that
>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>
>> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
>> ---
>> I'll additionally send kvm-unit-tests for testing this feature.
>>
>> arch/s390/include/asm/kvm_host.h | 1 +
>> arch/s390/kvm/kvm-s390.c | 2 ++
>> arch/s390/kvm/vsie.c | 2 ++
>> 3 files changed, 5 insertions(+)
(...)
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index b655a7d82bf0..aadd589a3755 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -3200,6 +3200,8 @@ static int kvm_s390_vcpu_setup(struct kvm_vcpu *vcpu)
>> vcpu->arch.sie_block->ecb |= ECB_SRSI;
>> if (test_kvm_facility(vcpu->kvm, 73))
>> vcpu->arch.sie_block->ecb |= ECB_TE;
Maybe add
/* no facility bit, but safe as the hardware may ignore it */
or something like that, so that we don't stumble over that in the future?
>> + if (!kvm_is_ucontrol(vcpu->kvm))
>> + vcpu->arch.sie_block->ecb |= ECB_SPECI;
>>
>> if (test_kvm_facility(vcpu->kvm, 8) && vcpu->kvm->arch.use_pfmfi)
>> vcpu->arch.sie_block->ecb2 |= ECB2_PFMFI;
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
next prev parent reply other threads:[~2021-07-07 8:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-06 11:47 [PATCH] KVM: s390: Enable specification exception interpretation Janis Schoetterl-Glausch
2021-07-06 11:52 ` Cornelia Huck
2021-07-06 11:56 ` Christian Borntraeger
2021-07-06 11:59 ` David Hildenbrand
2021-07-06 12:02 ` Christian Borntraeger
2021-07-06 15:16 ` David Hildenbrand
2021-07-06 15:27 ` Janis Schoetterl-Glausch
2021-07-07 7:26 ` David Hildenbrand
2021-07-06 11:55 ` David Hildenbrand
2021-07-07 8:30 ` Christian Borntraeger
2021-07-07 8:54 ` Cornelia Huck [this message]
2021-07-07 9:55 ` Janis Schoetterl-Glausch
2021-07-07 11:42 ` Cornelia Huck
2021-07-07 8:56 ` Janis Schoetterl-Glausch
2021-07-07 8:59 ` Christian Borntraeger
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