Re: [PATCH 3/3] KVM: Add helpers to wrap vcpu->srcu_idx and yell if it's abused

Fabiano Rosas
2022-04-19T17:20:28Z

Sean Christopherson <seanjc@google.com> writes:

> Add wrappers to acquire/release KVM's SRCU lock when stashing the index
> in vcpu->src_idx, along with rudimentary detection of illegal usage,
> e.g. re-acquiring SRCU and thus overwriting vcpu->src_idx. Because the
> SRCU index is (currently) either 0 or 1, illegal nesting bugs can go
> unnoticed for quite some time and only cause problems when the nested
> lock happens to get a different index.
>
> Wrap the WARNs in PROVE_RCU=y, and make them ONCE, otherwise KVM will
> likely yell so loudly that it will bring the kernel to its knees.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

For the powerpc part:

Tested-by: Fabiano Rosas <farosas@linux.ibm.com>

> ---
> arch/powerpc/kvm/book3s_64_mmu_radix.c | 9 +++++----
> arch/powerpc/kvm/book3s_hv_nested.c | 16 +++++++--------
> arch/powerpc/kvm/book3s_rtas.c | 4 ++--
> arch/powerpc/kvm/powerpc.c | 4 ++--
> arch/riscv/kvm/vcpu.c | 16 +++++++--------
> arch/riscv/kvm/vcpu_exit.c | 4 ++--
> arch/s390/kvm/interrupt.c | 4 ++--
> arch/s390/kvm/kvm-s390.c | 8 ++++----
> arch/s390/kvm/vsie.c | 4 ++--
> arch/x86/kvm/x86.c | 28 ++++++++++++--------------
> include/linux/kvm_host.h | 24 +++++++++++++++++++++-
> 11 files changed, 71 insertions(+), 50 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> index e4ce2a35483f..42851c32ff3b 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> @@ -168,9 +168,10 @@ int kvmppc_mmu_walk_radix_tree(struct kvm_vcpu *vcpu, gva_t eaddr,
> return -EINVAL;
> /* Read the entry from guest memory */
> addr = base + (index * sizeof(rpte));
> - vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> +
> + kvm_vcpu_srcu_read_lock(vcpu);
> ret = kvm_read_guest(kvm, addr, &rpte, sizeof(rpte));
> - srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (ret) {
> if (pte_ret_p)
> *pte_ret_p = addr;
> @@ -246,9 +247,9 @@ int kvmppc_mmu_radix_translate_table(struct kvm_vcpu *vcpu, gva_t eaddr,
>
> /* Read the table to find the root of the radix tree */
> ptbl = (table & PRTB_MASK) + (table_index * sizeof(entry));
> - vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> ret = kvm_read_guest(kvm, ptbl, &entry, sizeof(entry));
> - srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (ret)
> return ret;
>
> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
> index 9d373f8963ee..c943a051c6e7 100644
> --- a/arch/powerpc/kvm/book3s_hv_nested.c
> +++ b/arch/powerpc/kvm/book3s_hv_nested.c
> @@ -306,10 +306,10 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
> /* copy parameters in */
> hv_ptr = kvmppc_get_gpr(vcpu, 4);
> regs_ptr = kvmppc_get_gpr(vcpu, 5);
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> err = kvmhv_read_guest_state_and_regs(vcpu, &l2_hv, &l2_regs,
> hv_ptr, regs_ptr);
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (err)
> return H_PARAMETER;
>
> @@ -410,10 +410,10 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)
> byteswap_hv_regs(&l2_hv);
> byteswap_pt_regs(&l2_regs);
> }
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> err = kvmhv_write_guest_state_and_regs(vcpu, &l2_hv, &l2_regs,
> hv_ptr, regs_ptr);
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (err)
> return H_AUTHORITY;
>
> @@ -600,16 +600,16 @@ long kvmhv_copy_tofrom_guest_nested(struct kvm_vcpu *vcpu)
> goto not_found;
>
> /* Write what was loaded into our buffer back to the L1 guest */
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> rc = kvm_vcpu_write_guest(vcpu, gp_to, buf, n);
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (rc)
> goto not_found;
> } else {
> /* Load the data to be stored from the L1 guest into our buf */
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> rc = kvm_vcpu_read_guest(vcpu, gp_from, buf, n);
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (rc)
> goto not_found;
>
> diff --git a/arch/powerpc/kvm/book3s_rtas.c b/arch/powerpc/kvm/book3s_rtas.c
> index 0f847f1e5ddd..6808bda0dbc1 100644
> --- a/arch/powerpc/kvm/book3s_rtas.c
> +++ b/arch/powerpc/kvm/book3s_rtas.c
> @@ -229,9 +229,9 @@ int kvmppc_rtas_hcall(struct kvm_vcpu *vcpu)
> */
> args_phys = kvmppc_get_gpr(vcpu, 4) & KVM_PAM;
>
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> rc = kvm_read_guest(vcpu->kvm, args_phys, &args, sizeof(args));
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (rc)
> goto fail;
>
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 9772b176e406..fd88c2412e83 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -425,9 +425,9 @@ int kvmppc_ld(struct kvm_vcpu *vcpu, ulong *eaddr, int size, void *ptr,
> return EMULATE_DONE;
> }
>
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> rc = kvm_read_guest(vcpu->kvm, pte.raddr, ptr, size);
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (rc)
> return EMULATE_DO_MMIO;
>
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 2f1caf23eed4..256cf04ec01e 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -724,13 +724,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> /* Mark this VCPU ran at least once */
> vcpu->arch.ran_atleast_once = true;
>
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> /* Process MMIO value returned from user-space */
> if (run->exit_reason == KVM_EXIT_MMIO) {
> ret = kvm_riscv_vcpu_mmio_return(vcpu, vcpu->run);
> if (ret) {
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> return ret;
> }
> }
> @@ -739,13 +739,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> if (run->exit_reason == KVM_EXIT_RISCV_SBI) {
> ret = kvm_riscv_vcpu_sbi_return(vcpu, vcpu->run);
> if (ret) {
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> return ret;
> }
> }
>
> if (run->immediate_exit) {
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> return -EINTR;
> }
>
> @@ -784,7 +784,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> */
> vcpu->mode = IN_GUEST_MODE;
>
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> smp_mb__after_srcu_read_unlock();
>
> /*
> @@ -802,7 +802,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> vcpu->mode = OUTSIDE_GUEST_MODE;
> local_irq_enable();
> preempt_enable();
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> continue;
> }
>
> @@ -846,7 +846,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>
> preempt_enable();
>
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> ret = kvm_riscv_vcpu_exit(vcpu, run, &trap);
> }
> @@ -855,7 +855,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>
> vcpu_put(vcpu);
>
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
>
> return ret;
> }
> diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
> index 2d56faddb9d1..a72c15d4b42a 100644
> --- a/arch/riscv/kvm/vcpu_exit.c
> +++ b/arch/riscv/kvm/vcpu_exit.c
> @@ -456,9 +456,9 @@ static int stage2_page_fault(struct kvm_vcpu *vcpu, struct kvm_run *run,
> void kvm_riscv_vcpu_wfi(struct kvm_vcpu *vcpu)
> {
> if (!kvm_arch_vcpu_runnable(vcpu)) {
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> kvm_vcpu_halt(vcpu);
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> kvm_clear_request(KVM_REQ_UNHALT, vcpu);
> }
> }
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 9b30beac904d..af96dc0549a4 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -1334,11 +1334,11 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
> hrtimer_start(&vcpu->arch.ckc_timer, sltime, HRTIMER_MODE_REL);
> VCPU_EVENT(vcpu, 4, "enabled wait: %llu ns", sltime);
> no_timer:
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> kvm_vcpu_halt(vcpu);
> vcpu->valid_wakeup = false;
> __unset_cpu_idle(vcpu);
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> hrtimer_cancel(&vcpu->arch.ckc_timer);
> return 0;
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 156d1c25a3c1..da3dabda1a12 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4237,14 +4237,14 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
> * We try to hold kvm->srcu during most of vcpu_run (except when run-
> * ning the guest), so that memslots (and other stuff) are protected
> */
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> do {
> rc = vcpu_pre_run(vcpu);
> if (rc)
> break;
>
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> /*
> * As PF_VCPU will be used in fault handler, between
> * guest_enter and guest_exit should be no uaccess.
> @@ -4281,12 +4281,12 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
> __enable_cpu_timer_accounting(vcpu);
> guest_exit_irqoff();
> local_irq_enable();
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> rc = vcpu_post_run(vcpu, exit_reason);
> } while (!signal_pending(current) && !guestdbg_exit_pending(vcpu) && !rc);
>
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> return rc;
> }
>
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index acda4b6fc851..dada78b92691 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -1091,7 +1091,7 @@ static int do_vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>
> handle_last_fault(vcpu, vsie_page);
>
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
>
> /* save current guest state of bp isolation override */
> guest_bp_isolation = test_thread_flag(TIF_ISOLATE_BP_GUEST);
> @@ -1133,7 +1133,7 @@ static int do_vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> if (!guest_bp_isolation)
> clear_thread_flag(TIF_ISOLATE_BP_GUEST);
>
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> if (rc == -EINTR) {
> VCPU_EVENT(vcpu, 3, "%s", "machine check");
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f35fe09de59d..bc24b35c4e80 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10157,7 +10157,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> /* Store vcpu->apicv_active before vcpu->mode. */
> smp_store_release(&vcpu->mode, IN_GUEST_MODE);
>
> - srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
>
> /*
> * 1) We should set ->mode before checking ->requests. Please see
> @@ -10188,7 +10188,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> smp_wmb();
> local_irq_enable();
> preempt_enable();
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> r = 1;
> goto cancel_injection;
> }
> @@ -10314,7 +10314,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> local_irq_enable();
> preempt_enable();
>
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> /*
> * Profile KVM exit RIPs:
> @@ -10344,7 +10344,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> }
>
> /* Called within kvm->srcu read side. */
> -static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
> +static inline int vcpu_block(struct kvm_vcpu *vcpu)
> {
> bool hv_timer;
>
> @@ -10360,12 +10360,12 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
> if (hv_timer)
> kvm_lapic_switch_to_sw_timer(vcpu);
>
> - srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> if (vcpu->arch.mp_state == KVM_MP_STATE_HALTED)
> kvm_vcpu_halt(vcpu);
> else
> kvm_vcpu_block(vcpu);
> - vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> if (hv_timer)
> kvm_lapic_switch_to_hv_timer(vcpu);
> @@ -10407,7 +10407,6 @@ static inline bool kvm_vcpu_running(struct kvm_vcpu *vcpu)
> static int vcpu_run(struct kvm_vcpu *vcpu)
> {
> int r;
> - struct kvm *kvm = vcpu->kvm;
>
> vcpu->arch.l1tf_flush_l1d = true;
>
> @@ -10415,7 +10414,7 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
> if (kvm_vcpu_running(vcpu)) {
> r = vcpu_enter_guest(vcpu);
> } else {
> - r = vcpu_block(kvm, vcpu);
> + r = vcpu_block(vcpu);
> }
>
> if (r <= 0)
> @@ -10437,9 +10436,9 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
> }
>
> if (__xfer_to_guest_mode_work_pending()) {
> - srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> r = xfer_to_guest_mode_handle_work(vcpu);
> - vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> if (r)
> return r;
> }
> @@ -10542,7 +10541,6 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> {
> struct kvm_run *kvm_run = vcpu->run;
> - struct kvm *kvm = vcpu->kvm;
> int r;
>
> vcpu_load(vcpu);
> @@ -10550,7 +10548,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> kvm_run->flags = 0;
> kvm_load_guest_fpu(vcpu);
>
> - vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
> if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
> if (kvm_run->immediate_exit) {
> r = -EINTR;
> @@ -10562,9 +10560,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> */
> WARN_ON_ONCE(kvm_lapic_hv_timer_in_use(vcpu));
>
> - srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
> kvm_vcpu_block(vcpu);
> - vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
> + kvm_vcpu_srcu_read_lock(vcpu);
>
> if (kvm_apic_accept_events(vcpu) < 0) {
> r = 0;
> @@ -10625,7 +10623,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> if (kvm_run->kvm_valid_regs)
> store_regs(vcpu);
> post_kvm_run_save(vcpu);
> - srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
> + kvm_vcpu_srcu_read_unlock(vcpu);
>
> kvm_sigset_deactivate(vcpu);
> vcpu_put(vcpu);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 252ee4a61b58..76fc7233bd6a 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -315,7 +315,10 @@ struct kvm_vcpu {
> int cpu;
> int vcpu_id; /* id given by userspace at creation */
> int vcpu_idx; /* index in kvm->vcpus array */
> - int srcu_idx;
> + int ____srcu_idx; /* Don't use this directly. You've been warned. */
> +#ifdef CONFIG_PROVE_RCU
> + int srcu_depth;
> +#endif
> int mode;
> u64 requests;
> unsigned long guest_debug;
> @@ -841,6 +844,25 @@ static inline void kvm_vm_bugged(struct kvm *kvm)
> unlikely(__ret); \
> })
>
> +static inline void kvm_vcpu_srcu_read_lock(struct kvm_vcpu *vcpu)
> +{
> +#ifdef CONFIG_PROVE_RCU
> + WARN_ONCE(vcpu->srcu_depth++,
> + "KVM: Illegal vCPU srcu_idx LOCK, depth=%d", vcpu->srcu_depth - 1);
> +#endif
> + vcpu->____srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> +}
> +
> +static inline void kvm_vcpu_srcu_read_unlock(struct kvm_vcpu *vcpu)
> +{
> + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->____srcu_idx);
> +
> +#ifdef CONFIG_PROVE_RCU
> + WARN_ONCE(--vcpu->srcu_depth,
> + "KVM: Illegal vCPU srcu_idx UNLOCK, depth=%d", vcpu->srcu_depth);
> +#endif
> +}
> +
> static inline bool kvm_dirty_log_manual_protect_and_init_set(struct kvm *kvm)
> {
> return !!(kvm->manual_dirty_log_protect & KVM_DIRTY_LOG_INITIALLY_SET);