kvm_get_kvm() kvm_put_kvm() -----Original Message----- From: Nikita Leshenko [mailto:[email protected]] Sent: Tuesday, September 4, 2018 3:57 PM To: Wu, Fengguang <[email protected]> Cc: Andrew Morton <[email protected]>; Linux Memory Management List <[email protected]>; Peng, DongX <[email protected]>; Liu, Jingqi <[email protected]>; Dong, Eddie <[email protected]>; Hansen, Dave <[email protected]>; Huang, Ying <[email protected]>; Brendan Gregg <[email protected]>; [email protected]; LKML <[email protected]> Subject: Re: [RFC][PATCH 3/5] [PATCH 3/5] kvm-ept-idle: HVA indexed EPT read
On 1 Sep 2018, at 13:28, Fengguang Wu <[email protected]> wrote: > +static ssize_t ept_idle_read(struct file *file, char *buf, > + size_t count, loff_t *ppos) > +{ > + struct task_struct *task = file->private_data; > + struct ept_idle_ctrl *eic; > + unsigned long hva_start = *ppos << BITMAP_BYTE2PVA_SHIFT; > + unsigned long hva_end = hva_start + (count << BITMAP_BYTE2PVA_SHIFT); > + int ret; > + > + if (*ppos % IDLE_BITMAP_CHUNK_SIZE || > + count % IDLE_BITMAP_CHUNK_SIZE) > + return -EINVAL; > + > + eic = kzalloc(sizeof(*eic), GFP_KERNEL); > + if (!eic) > + return -EBUSY; > + > + eic->buf = buf; > + eic->buf_size = count; > + eic->kvm = task_kvm(task); > + if (!eic->kvm) { > + ret = -EINVAL; > + goto out_free; > + } I think you need to increment the refcount while using kvm, otherwise kvm can be destroyed from another thread while you're walking it. -Nikita > + > + ret = ept_idle_walk_hva_range(eic, hva_start, hva_end); > + if (ret) > + goto out_free; > + > + ret = eic->bytes_copied; > + *ppos += ret; > +out_free: > + kfree(eic); > + > + return ret; > +}
