Re: [PATCH v7] KVM: s390: Add new reset vcpu API

Janosch Frank
2020-01-10T12:24:26Z

[-- Attachment #1.1: Type: text/plain, Size: 7587 bytes --]

On 1/10/20 1:11 PM, Thomas Huth wrote:
> On 10/01/2020 12.45, Janosch Frank wrote:
>> The architecture states that we need to reset local IRQs for all CPU
>> resets. Because the old reset interface did not support the normal CPU
>> reset we never did that on a normal reset.
>>
>> Let's implement an interface for the missing normal and clear resets
>> and reset all local IRQs, registers and control structures as stated
>> in the architecture.
>>
>> Userspace might already reset the registers via the vcpu run struct,
>> but as we need the interface for the interrupt clearing part anyway,
>> we implement the resets fully and don't rely on userspace to reset the
>> rest.
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>> ---
>> Documentation/virt/kvm/api.txt | 43 +++++++++++++
>> arch/s390/kvm/kvm-s390.c | 112 +++++++++++++++++++++++----------
>> include/uapi/linux/kvm.h | 5 ++
>> 3 files changed, 127 insertions(+), 33 deletions(-)
>>
>> diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
>> index ebb37b34dcfc..73448764f544 100644
>> --- a/Documentation/virt/kvm/api.txt
>> +++ b/Documentation/virt/kvm/api.txt
>> @@ -4168,6 +4168,42 @@ This ioctl issues an ultravisor call to terminate the secure guest,
>> unpins the VPA pages and releases all the device pages that are used to
>> track the secure pages by hypervisor.
>>
>> +4.122 KVM_S390_NORMAL_RESET
>> +
>> +Capability: KVM_CAP_S390_VCPU_RESETS
>> +Architectures: s390
>> +Type: vcpu ioctl
>> +Parameters: none
>> +Returns: 0
>> +
>> +This ioctl resets VCPU registers and control structures according to
>> +the cpu reset definition in the POP (Principles Of Operation).
>> +
>> +4.123 KVM_S390_INITIAL_RESET
>> +
>> +Capability: none
>> +Architectures: s390
>> +Type: vcpu ioctl
>> +Parameters: none
>> +Returns: 0
>> +
>> +This ioctl resets VCPU registers and control structures according to
>> +the initial cpu reset definition in the POP. However, the cpu is not
>> +put into ESA mode. This reset is a superset of the normal reset.
>> +
>> +4.124 KVM_S390_CLEAR_RESET
>> +
>> +Capability: KVM_CAP_S390_VCPU_RESETS
>> +Architectures: s390
>> +Type: vcpu ioctl
>> +Parameters: none
>> +Returns: 0
>> +
>> +This ioctl resets VCPU registers and control structures according to
>> +the clear cpu reset definition in the POP. However, the cpu is not put
>> +into ESA mode. This reset is a superset of the initial reset.
>> +
>> +
>> 5. The kvm_run structure
>> ------------------------
>>
>> @@ -5396,3 +5432,10 @@ handling by KVM (as some KVM hypercall may be mistakenly treated as TLB
>> flush hypercalls by Hyper-V) so userspace should disable KVM identification
>> in CPUID and only exposes Hyper-V identification. In this case, guest
>> thinks it's running on Hyper-V and only use Hyper-V hypercalls.
>> +
>> +8.22 KVM_CAP_S390_VCPU_RESETS
>> +
>> +Architectures: s390
>> +
>> +This capability indicates that the KVM_S390_NORMAL_RESET and
>> +KVM_S390_CLEAR_RESET ioctls are available.
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index d9e6bf3d54f0..5640f3d6f98d 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -529,6 +529,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>> case KVM_CAP_S390_CMMA_MIGRATION:
>> case KVM_CAP_S390_AIS:
>> case KVM_CAP_S390_AIS_MIGRATION:
>> + case KVM_CAP_S390_VCPU_RESETS:
>> r = 1;
>> break;
>> case KVM_CAP_S390_HPAGE_1M:
>> @@ -2844,35 +2845,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>>
>> }
>>
>> -static void kvm_s390_vcpu_initial_reset(struct kvm_vcpu *vcpu)
>> -{
>> - /* this equals initial cpu reset in pop, but we don't switch to ESA */
>> - vcpu->arch.sie_block->gpsw.mask = 0UL;
>> - vcpu->arch.sie_block->gpsw.addr = 0UL;
>> - kvm_s390_set_prefix(vcpu, 0);
>> - kvm_s390_set_cpu_timer(vcpu, 0);
>> - vcpu->arch.sie_block->ckc = 0UL;
>> - vcpu->arch.sie_block->todpr = 0;
>> - memset(vcpu->arch.sie_block->gcr, 0, 16 * sizeof(__u64));
>> - vcpu->arch.sie_block->gcr[0] = CR0_UNUSED_56 |
>> - CR0_INTERRUPT_KEY_SUBMASK |
>> - CR0_MEASUREMENT_ALERT_SUBMASK;
>> - 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();
>> - current->thread.fpu.fpc = 0;
>> - vcpu->arch.sie_block->gbea = 1;
>> - vcpu->arch.sie_block->pp = 0;
>> - vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
>> - vcpu->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;
>> - kvm_clear_async_pf_completion_queue(vcpu);
>> - if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm))
>> - kvm_s390_vcpu_stop(vcpu);
>> - kvm_s390_clear_local_irqs(vcpu);
>> -}
>> -
>> void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
>> {
>> mutex_lock(&vcpu->kvm->lock);
>> @@ -3287,10 +3259,75 @@ static int kvm_arch_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu,
>> return r;
>> }
>>
>> -static int kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>> +static void kvm_arch_vcpu_ioctl_normal_reset(struct kvm_vcpu *vcpu)
>> {
>> - kvm_s390_vcpu_initial_reset(vcpu);
>> - return 0;
>> + vcpu->arch.sie_block->gpsw.mask = ~PSW_MASK_RI;
>> + vcpu->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;
>> + memset(vcpu->run->s.regs.riccb, 0, sizeof(vcpu->run->s.regs.riccb));
>> +
>> + kvm_clear_async_pf_completion_queue(vcpu);
>> + if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm))
>> + kvm_s390_vcpu_stop(vcpu);
>> + kvm_s390_clear_local_irqs(vcpu);
>> +}
>> +
>> +static void kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>> +{
>> + /* Initial reset is a superset of the normal reset */
>> + kvm_arch_vcpu_ioctl_normal_reset(vcpu);
>> +
>> + /* this equals initial cpu reset in pop, but we don't switch to ESA */
>> + vcpu->arch.sie_block->gpsw.mask = 0UL;
>> + vcpu->arch.sie_block->gpsw.addr = 0UL;
>> + kvm_s390_set_prefix(vcpu, 0);
>> + kvm_s390_set_cpu_timer(vcpu, 0);
>> + vcpu->arch.sie_block->ckc = 0UL;
>> + vcpu->arch.sie_block->todpr = 0;
>> + memset(vcpu->arch.sie_block->gcr, 0, 16 * sizeof(__u64));
>> + vcpu->arch.sie_block->gcr[0] = CR0_UNUSED_56 |
>> + CR0_INTERRUPT_KEY_SUBMASK |
>> + CR0_MEASUREMENT_ALERT_SUBMASK;
>> + 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();
>> + current->thread.fpu.fpc = 0;
>> + vcpu->arch.sie_block->gbea = 1;
>> + vcpu->arch.sie_block->pp = 0;
>> + vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
>> +}
>> +
>> +static void kvm_arch_vcpu_ioctl_clear_reset(struct kvm_vcpu *vcpu)
>> +{
>> + struct kvm_sync_regs *regs = &vcpu->run->s.regs;
>> +
>> + /* Clear reset is a superset of the initial reset */
>> + kvm_arch_vcpu_ioctl_normal_reset(vcpu);
>
> s/kvm_arch_vcpu_ioctl_normal_reset/kvm_arch_vcpu_ioctl_initial_reset/

-_-
It seems like my vacation was not enough...

>
>> + memset(&regs->gprs, 0, sizeof(regs->gprs));
>> + /* Will be picked up because of save_fpu_regs() in the initial reset */
>> + memset(&current->thread.fpu.vxrs, 0, sizeof(current->thread.fpu.vxrs));
>
> I'm still not 100% sure about whether current->thread.fpu.vxrs is always
> fine here? But I hope Christian can give an ACK for that...
>
> Thomas
>

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]