diff options
| -rw-r--r-- | Documentation/virtual/kvm/api.txt | 40 | ||||
| -rw-r--r-- | arch/x86/include/uapi/asm/kvm.h | 19 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 102 |
3 files changed, 145 insertions, 16 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 55867a2a460c..98de5061307d 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -4110,6 +4110,46 @@ Once this is done the KVM_REG_MIPS_VEC_* and KVM_REG_MIPS_MSA_* registers can be accessed, and the Config5.MSAEn bit is accessible via the KVM API and also from the guest. +6.74 KVM_CAP_SYNC_REGS +Architectures: s390, x86 +Target: s390: always enabled, x86: vcpu +Parameters: none +Returns: x86: KVM_CHECK_EXTENSION returns a bit-array indicating which register +sets are supported (bitfields defined in arch/x86/include/uapi/asm/kvm.h). + +As described above in the kvm_sync_regs struct info in section 5 (kvm_run): +KVM_CAP_SYNC_REGS "allow[s] userspace to access certain guest registers +without having to call SET/GET_*REGS". This reduces overhead by eliminating +repeated ioctl calls for setting and/or getting register values. This is +particularly important when userspace is making synchronous guest state +modifications, e.g. when emulating and/or intercepting instructions in +userspace. + +For s390 specifics, please refer to the source code. + +For x86: +- the register sets to be copied out to kvm_run are selectable + by userspace (rather that all sets being copied out for every exit). +- vcpu_events are available in addition to regs and sregs. + +For x86, the 'kvm_valid_regs' field of struct kvm_run is overloaded to +function as an input bit-array field set by userspace to indicate the +specific register sets to be copied out on the next exit. + +To indicate when userspace has modified values that should be copied into +the vCPU, the all architecture bitarray field, 'kvm_dirty_regs' must be set. +This is done using the same bitflags as for the 'kvm_valid_regs' field. +If the dirty bit is not set, then the register set values will not be copied +into the vCPU even if they've been modified. + +Unused bitfields in the bitarrays must be set to zero. + +struct kvm_sync_regs { + struct kvm_regs regs; + struct kvm_sregs sregs; + struct kvm_vcpu_events events; +}; + 7. Capabilities that can be enabled on VMs ------------------------------------------ diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h index f3a960488eae..c535c2fdea13 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -354,8 +354,25 @@ struct kvm_xcrs { __u64 padding[16]; }; -/* definition of registers in kvm_run */ +#define KVM_SYNC_X86_REGS (1UL << 0) +#define KVM_SYNC_X86_SREGS (1UL << 1) +#define KVM_SYNC_X86_EVENTS (1UL << 2) + +#define KVM_SYNC_X86_VALID_FIELDS \ + (KVM_SYNC_X86_REGS| \ + KVM_SYNC_X86_SREGS| \ + KVM_SYNC_X86_EVENTS) + +/* kvm_sync_regs struct included by kvm_run struct */ struct kvm_sync_regs { + /* Members of this structure are potentially malicious. + * Care must be taken by code reading, esp. interpreting, + * data fields from them inside KVM to prevent TOCTOU and + * double-fetch types of vulnerabilities. + */ + struct kvm_regs regs; + struct kvm_sregs sregs; + struct kvm_vcpu_events events; }; #define KVM_X86_QUIRK_LINT0_REENABLED (1 << 0) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 3b6b7ee9fa8f..967cc1388770 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -102,6 +102,8 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu); static void process_nmi(struct kvm_vcpu *vcpu); static void enter_smm(struct kvm_vcpu *vcpu); static void __kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags); +static void store_regs(struct kvm_vcpu *vcpu); +static int sync_regs(struct kvm_vcpu *vcpu); struct kvm_x86_ops *kvm_x86_ops __read_mostly; EXPORT_SYMBOL_GPL(kvm_x86_ops); @@ -2829,6 +2831,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_GET_MSR_FEATURES: r = 1; break; + case KVM_CAP_SYNC_REGS: + r = KVM_SYNC_X86_VALID_FIELDS; + break; case KVM_CAP_ADJUST_CLOCK: r = KVM_CLOCK_TSC_STABLE; break; @@ -7510,7 +7515,6 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu) return 0; } - int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) { int r; @@ -7536,6 +7540,17 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) goto out; } + if (vcpu->run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) { + r = -EINVAL; + goto out; + } + + if (vcpu->run->kvm_dirty_regs) { + r = sync_regs(vcpu); + if (r != 0) + goto out; + } + /* re-sync apic's tpr */ if (!lapic_in_kernel(vcpu)) { if (kvm_set_cr8(vcpu, kvm_run->cr8) != 0) { @@ -7560,6 +7575,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) out: kvm_put_guest_fpu(vcpu); + if (vcpu->run->kvm_valid_regs) + store_regs(vcpu); post_kvm_run_save(vcpu); kvm_sigset_deactivate(vcpu); @@ -7567,10 +7584,8 @@ out: return r; } -int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) +static void __get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) { - vcpu_load(vcpu); - if (vcpu->arch.emulate_regs_need_sync_to_vcpu) { /* * We are here if userspace calls get_regs() in the middle of @@ -7603,15 +7618,18 @@ int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) regs->rip = kvm_rip_read(vcpu); regs->rflags = kvm_get_rflags(vcpu); +} +int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) +{ + vcpu_load(vcpu); + __get_regs(vcpu, regs); vcpu_put(vcpu); return 0; } -int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) +static void __set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) { - vcpu_load(vcpu); - vcpu->arch.emulate_regs_need_sync_from_vcpu = true; vcpu->arch.emulate_regs_need_sync_to_vcpu = false; @@ -7640,7 +7658,12 @@ int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) vcpu->arch.exception.pending = false; kvm_make_request(KVM_REQ_EVENT, vcpu); +} +int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) +{ + vcpu_load(vcpu); + __set_regs(vcpu, regs); vcpu_put(vcpu); return 0; } @@ -7655,13 +7678,10 @@ void kvm_get_cs_db_l_bits(struct kvm_vcpu *vcpu, int *db, int *l) } EXPORT_SYMBOL_GPL(kvm_get_cs_db_l_bits); -int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu, - struct kvm_sregs *sregs) +static void __get_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs) { struct desc_ptr dt; - vcpu_load(vcpu); - kvm_get_segment(vcpu, &sregs->cs, VCPU_SREG_CS); kvm_get_segment(vcpu, &sregs->ds, VCPU_SREG_DS); kvm_get_segment(vcpu, &sregs->es, VCPU_SREG_ES); @@ -7692,7 +7712,13 @@ int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu, if (vcpu->arch.interrupt.pending && !vcpu->arch.interrupt.soft) set_bit(vcpu->arch.interrupt.nr, (unsigned long *)sregs->interrupt_bitmap); +} +int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu, + struct kvm_sregs *sregs) +{ + vcpu_load(vcpu); + __get_sregs(vcpu, sregs); vcpu_put(vcpu); return 0; } @@ -7787,8 +7813,7 @@ int kvm_valid_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs) return 0; } -int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, - struct kvm_sregs *sregs) +static int __set_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs) { struct msr_data apic_base_msr; int mmu_reset_needed = 0; @@ -7796,8 +7821,6 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, struct desc_ptr dt; int ret = -EINVAL; - vcpu_load(vcpu); - if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) && (sregs->cr4 & X86_CR4_OSXSAVE)) goto out; @@ -7876,6 +7899,16 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, ret = 0; out: + return ret; +} + +int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, + struct kvm_sregs *sregs) +{ + int ret; + + vcpu_load(vcpu); + ret = __set_sregs(vcpu, sregs); vcpu_put(vcpu); return ret; } @@ -8002,6 +8035,45 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu) return 0; } +static void store_regs(struct kvm_vcpu *vcpu) +{ + BUILD_BUG_ON(sizeof(struct kvm_sync_regs) > SYNC_REGS_SIZE_BYTES); + + if (vcpu->run->kvm_valid_regs & KVM_SYNC_X86_REGS) + __get_regs(vcpu, &vcpu->run->s.regs.regs); + + if (vcpu->run->kvm_valid_regs & KVM_SYNC_X86_SREGS) + __get_sregs(vcpu, &vcpu->run->s.regs.sregs); + + if (vcpu->run->kvm_valid_regs & KVM_SYNC_X86_EVENTS) + kvm_vcpu_ioctl_x86_get_vcpu_events( + vcpu, &vcpu->run->s.regs.events); +} + +static int sync_regs(struct kvm_vcpu *vcpu) +{ + if (vcpu->run->kvm_dirty_regs & ~KVM_SYNC_X86_VALID_FIELDS) + return -EINVAL; + + if (vcpu->run->kvm_dirty_regs & KVM_SYNC_X86_REGS) { + __set_regs(vcpu, &vcpu->run->s.regs.regs); + vcpu->run->kvm_dirty_regs &= ~KVM_SYNC_X86_REGS; + } + if (vcpu->run->kvm_dirty_regs & KVM_SYNC_X86_SREGS) { + if (__set_sregs(vcpu, &vcpu->run->s.regs.sregs)) + return -EINVAL; + vcpu->run->kvm_dirty_regs &= ~KVM_SYNC_X86_SREGS; + } + if (vcpu->run->kvm_dirty_regs & KVM_SYNC_X86_EVENTS) { + if (kvm_vcpu_ioctl_x86_set_vcpu_events( + vcpu, &vcpu->run->s.regs.events)) + return -EINVAL; + vcpu->run->kvm_dirty_regs &= ~KVM_SYNC_X86_EVENTS; + } + + return 0; +} + static void fx_init(struct kvm_vcpu *vcpu) { fpstate_init(&vcpu->arch.guest_fpu.state); |