Re: [PATCH v2] KVM: s390: wire up bpb feature

Christian Borntraeger
2018-01-17T21:43:24Z

On 01/17/2018 02:51 PM, David Hildenbrand wrote:
> On 17.01.2018 14:44, Christian Borntraeger wrote:
>> The new firmware interfaces for branch prediction behaviour changes
>> are transparently available for the guest. Nevertheless, there is
>> new state attached that should be migrated and properly resetted.
>> Provide a mechanism for handling reset, migration and VSIE.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>> v1->v2: - review feedback from David
>> - rename seb(c) into bpb(c)
>> arch/s390/include/asm/kvm_host.h | 3 ++-
>> arch/s390/include/uapi/asm/kvm.h | 5 ++++-
>> arch/s390/kvm/kvm-s390.c | 12 ++++++++++++
>> arch/s390/kvm/vsie.c | 10 ++++++++++
>> include/uapi/linux/kvm.h | 1 +
>> 5 files changed, 29 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
>> index e14f381..c1b0a9a 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
>> @@ -207,7 +207,8 @@ struct kvm_s390_sie_block {
>> __u16 ipa; /* 0x0056 */
>> __u32 ipb; /* 0x0058 */
>> __u32 scaoh; /* 0x005c */
>> - __u8 reserved60; /* 0x0060 */
>> +#define FPF_BPBC 0x20
>> + __u8 fpf; /* 0x0060 */
>> #define ECB_GS 0x40
>> #define ECB_TE 0x10
>> #define ECB_SRSI 0x04
>> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
>> index 38535a57..4cdaa55 100644
>> --- a/arch/s390/include/uapi/asm/kvm.h
>> +++ b/arch/s390/include/uapi/asm/kvm.h
>> @@ -224,6 +224,7 @@ struct kvm_guest_debug_arch {
>> #define KVM_SYNC_RICCB (1UL << 7)
>> #define KVM_SYNC_FPRS (1UL << 8)
>> #define KVM_SYNC_GSCB (1UL << 9)
>> +#define KVM_SYNC_BPBC (1UL << 10)
>> /* length and alignment of the sdnx as a power of two */
>> #define SDNXC 8
>> #define SDNXL (1UL << SDNXC)
>> @@ -247,7 +248,9 @@ struct kvm_sync_regs {
>> };
>> __u8 reserved[512]; /* for future vector expansion */
>> __u32 fpc; /* valid on KVM_SYNC_VRS or KVM_SYNC_FPRS */
>> - __u8 padding1[52]; /* riccb needs to be 64byte aligned */
>> + __u8 bpbc : 1; /* bp mode */
>> + __u8 reserved2 : 7;
>> + __u8 padding1[51]; /* riccb needs to be 64byte aligned */
>> __u8 riccb[64]; /* runtime instrumentation controls block */
>> __u8 padding2[192]; /* sdnx needs to be 256byte aligned */
>> union {
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 2c93cbb..2598cf243 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -421,6 +421,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>> case KVM_CAP_S390_GS:
>> r = test_facility(133);
>> break;
>> + case KVM_CAP_S390_BPB:
>> + r = test_facility(82);
>> + break;
>> default:
>> r = 0;
>> }
>> @@ -2198,6 +2201,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
>> kvm_s390_set_prefix(vcpu, 0);
>> if (test_kvm_facility(vcpu->kvm, 64))
>> vcpu->run->kvm_valid_regs |= KVM_SYNC_RICCB;
>> + if (test_kvm_facility(vcpu->kvm, 82))
>> + vcpu->run->kvm_valid_regs |= KVM_SYNC_BPBC;
>> if (test_kvm_facility(vcpu->kvm, 133))
>> vcpu->run->kvm_valid_regs |= KVM_SYNC_GSCB;
>> /* fprs can be synchronized via vrs, even if the guest has no vx. With
>> @@ -2339,6 +2344,7 @@ static void kvm_s390_vcpu_initial_reset(struct kvm_vcpu *vcpu)
>> 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))
>> @@ -3298,6 +3304,11 @@ static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> vcpu->arch.sie_block->ecd |= ECD_HOSTREGMGMT;
>> vcpu->arch.gs_enabled = 1;
>> }
>> + if ((kvm_run->kvm_dirty_regs & KVM_SYNC_BPBC) &&
>> + test_kvm_facility(vcpu->kvm, 82)) {
>> + vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
>> + vcpu->arch.sie_block->fpf |= kvm_run->s.regs.bpbc ? FPF_BPBC : 0;
>> + }
>> save_access_regs(vcpu->arch.host_acrs);
>> restore_access_regs(vcpu->run->s.regs.acrs);
>> /* save host (userspace) fprs/vrs */
>> @@ -3344,6 +3355,7 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> kvm_run->s.regs.pft = vcpu->arch.pfault_token;
>> kvm_run->s.regs.pfs = vcpu->arch.pfault_select;
>> kvm_run->s.regs.pfc = vcpu->arch.pfault_compare;
>> + kvm_run->s.regs.bpbc = (vcpu->arch.sie_block->fpf & FPF_BPBC) == FPF_BPBC;
>> save_access_regs(vcpu->run->s.regs.acrs);
>> restore_access_regs(vcpu->arch.host_acrs);
>> /* Save guest register state */
>> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
>> index 5d6ae03..7513483 100644
>> --- a/arch/s390/kvm/vsie.c
>> +++ b/arch/s390/kvm/vsie.c
>> @@ -223,6 +223,12 @@ static void unshadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>> memcpy(scb_o->gcr, scb_s->gcr, 128);
>> scb_o->pp = scb_s->pp;
>>
>> + /* branch prediction */
>> + if (test_kvm_facility(vcpu->kvm, 82)) {
>> + scb_o->fpf &= ~FPF_BPBC;
>> + scb_o->fpf |= scb_s->fpf & FPF_BPBC;
>> + }
>> +
>> /* interrupt intercept */
>> switch (scb_s->icptcode) {
>> case ICPT_PROGI:
>> @@ -265,6 +271,7 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>> scb_s->ecb3 = 0;
>> scb_s->ecd = 0;
>> scb_s->fac = 0;
>> + scb_s->fpf = 0;
>>
>> rc = prepare_cpuflags(vcpu, vsie_page);
>> if (rc)
>> @@ -324,6 +331,9 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>> prefix_unmapped(vsie_page);
>> scb_s->ecb |= scb_o->ecb & ECB_TE;
>> }
>> + /* branch prediction */
>> + if (test_kvm_facility(vcpu->kvm, 82))
>> + scb_s->fpf |= scb_o->fpf & FPF_BPBC;
>> /* SIMD */
>> if (test_kvm_facility(vcpu->kvm, 129)) {
>> scb_s->eca |= scb_o->eca & ECA_VX;
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 496e59a..79f6050 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -932,6 +932,7 @@ struct kvm_ppc_resize_hpt {
>> #define KVM_CAP_HYPERV_SYNIC2 148
>> #define KVM_CAP_HYPERV_VP_INDEX 149
>> #define KVM_CAP_S390_AIS_MIGRATION 150
>> +#define KVM_CAP_S390_BPB 151
>>
>> #ifdef KVM_CAP_IRQ_ROUTING
>>
>>
>
> Reviewed-by: David Hildenbrand <david@redhat.com>

Thanks.

Conny can you review and ack as well?

Paolo, Radim,

As the other patches need to sync on the ifetch/nospec/gmb naming I have changed my mind. :-)
This patch is independent from the other patches (as it just provides the guest facilities not caring
about what the host does).

It seems that you do a kvm pull request for 4.15 anyway (for power), so it might make sense to
apply this patch as well for 4.15. this will make it easier to also upstream the QEMU part in time
as we need the uabi interfaces.

Christian