Re: [PATCH 5/6] KVM: s390: wire up seb feature

David Hildenbrand
2018-01-17T11:33:52Z

> #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..20b9e9f 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_SEBC (1UL << 10)
> /* length and alignment of the sdnx as a power of two */
> #define SDNXC 8
> #define SDNXL (1UL << SDNXC)
> @@ -247,7 +248,8 @@ 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 sebc:1; /* spec blocking */

do you want to define the unused bits as reserved? Nicer to read IMHO

(especially also using spaces "sebc : 1")

> + __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..0c18f73 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_SEB:
> + 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_SEBC;
> 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_SEBC;
> 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 +3304,10 @@ 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_SEBC) {

We should test for test_facility(82). Otherwise user space can enable
undefined bits in the SCB on machines with !facility 82.

> + vcpu->arch.sie_block->fpf &= ~FPF_SEBC;
> + vcpu->arch.sie_block->fpf |= kvm_run->s.regs.sebc ? FPF_SEBC : 0;
> + }
> save_access_regs(vcpu->arch.host_acrs);
> restore_access_regs(vcpu->run->s.regs.acrs);
> /* save host (userspace) fprs/vrs */
> @@ -3344,6 +3354,7 @@ 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.sebc = (vcpu->arch.sie_block->fpf & FPF_SEBC) == FPF_SEBC;
> 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..10ea208 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -223,6 +223,10 @@ 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;
>
> + /* speculative blocking */

This field should only be written back with test_kvm_facility(vcpu->kvm, 82)

(no public documentation, this looks like the SIE can modify this field?
Triggered by which instruction?)

> + scb_o->fpf &= ~FPF_SEBC;
> + scb_o->fpf |= scb_s->fpf & FPF_SEBC;
> +
> /* interrupt intercept */
> switch (scb_s->icptcode) {
> case ICPT_PROGI:
> @@ -265,6 +269,7 @@ 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 +329,9 @@ 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;
> }
> + /* speculative blocking */
> + if (test_kvm_facility(vcpu->kvm, 82))
> + scb_s->fpf |= scb_o->fpf & FPF_SEBC;
> /* SIMD */
> if (test_kvm_facility(vcpu->kvm, 129)) {
> scb_s->eca |= scb_o->eca & ECA_VX;

--

Thanks,

David / dhildenb