Wanpeng Li <kernellwp@xxxxxxxxx> writes:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> WARNING: suspicious RCU usage
> 5.13.0-rc1 #4 Not tainted
> -----------------------------
> ./include/linux/kvm_host.h:710 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 2, debug_locks = 1
> 1 lock held by hyperv_clock/8318:
> #0: ffffb6b8cb05a7d8 (&hv->hv_lock){+.+.}-{3:3}, at: kvm_hv_invalidate_tsc_page+0x3e/0xa0 [kvm]
>
> stack backtrace:
> CPU: 3 PID: 8318 Comm: hyperv_clock Not tainted 5.13.0-rc1 #4
> Call Trace:
> dump_stack+0x87/0xb7
> lockdep_rcu_suspicious+0xce/0xf0
> kvm_write_guest_page+0x1c1/0x1d0 [kvm]
> kvm_write_guest+0x50/0x90 [kvm]
> kvm_hv_invalidate_tsc_page+0x79/0xa0 [kvm]
> kvm_gen_update_masterclock+0x1d/0x110 [kvm]
> kvm_arch_vm_ioctl+0x2a7/0xc50 [kvm]
> kvm_vm_ioctl+0x123/0x11d0 [kvm]
> __x64_sys_ioctl+0x3ed/0x9d0
> do_syscall_64+0x3d/0x80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> kvm_memslots() will be called by kvm_write_guest(), so we should take the srcu lock.
>
> Fixes: e880c6ea5 (KVM: x86: hyper-v: Prevent using not-yet-updated TSC page by secondary CPUs)
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
> arch/x86/kvm/hyperv.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
> index f98370a3..f00830e 100644
> --- a/arch/x86/kvm/hyperv.c
> +++ b/arch/x86/kvm/hyperv.c
> @@ -1172,6 +1172,7 @@ void kvm_hv_invalidate_tsc_page(struct kvm *kvm)
> {
> struct kvm_hv *hv = to_kvm_hv(kvm);
> u64 gfn;
> + int idx;
>
> if (hv->hv_tsc_page_status == HV_TSC_PAGE_BROKEN ||
> hv->hv_tsc_page_status == HV_TSC_PAGE_UNSET ||
> @@ -1190,9 +1191,16 @@ void kvm_hv_invalidate_tsc_page(struct kvm *kvm)
> gfn = hv->hv_tsc_page >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;
>
> hv->tsc_ref.tsc_sequence = 0;
> +
> + /*
> + * Take the srcu lock as memslots will be accessed to check the gfn
> + * cache generation against the memslots generation.
> + */
> + idx = srcu_read_lock(&kvm->srcu);
> if (kvm_write_guest(kvm, gfn_to_gpa(gfn),
> &hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence)))
> hv->hv_tsc_page_status = HV_TSC_PAGE_BROKEN;
> + srcu_read_unlock(&kvm->srcu, idx);
>
> out_unlock:
> mutex_unlock(&hv->hv_lock);
Thanks!
Do we need to do the same in kvm_hv_setup_tsc_page()?
--
Vitaly
