Excerpts from Haren Myneni's message of June 13, 2021 8:57 pm: > > Take pid and mm references when each window opens and drops during > close. This functionality is needed for powerNV and pseries. So > this patch defines the existing code as functions in common book3s > platform vas-api.c > > Signed-off-by: Haren Myneni <haren@xxxxxxxxxxxxx> Reviewed-by: Nicholas Piggin <npiggin@xxxxxxxxx> Thanks, Nick > --- > arch/powerpc/include/asm/vas.h | 40 +++++++++++++++ > arch/powerpc/platforms/book3s/vas-api.c | 39 +++++++++++++++ > arch/powerpc/platforms/powernv/vas-fault.c | 10 ++-- > arch/powerpc/platforms/powernv/vas-window.c | 55 ++------------------- > arch/powerpc/platforms/powernv/vas.h | 6 +-- > 5 files changed, 91 insertions(+), 59 deletions(-) > > diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h > index 85318d7446c7..163460cff59b 100644 > --- a/arch/powerpc/include/asm/vas.h > +++ b/arch/powerpc/include/asm/vas.h > @@ -5,6 +5,9 @@ > > #ifndef _ASM_POWERPC_VAS_H > #define _ASM_POWERPC_VAS_H > +#include <linux/sched/mm.h> > +#include <linux/mmu_context.h> > +#include <asm/icswx.h> > #include <uapi/asm/vas-api.h> > > struct vas_window; > @@ -49,6 +52,17 @@ enum vas_cop_type { > VAS_COP_TYPE_MAX, > }; > > +/* > + * User space VAS windows are opened by tasks and take references > + * to pid and mm until windows are closed. > + * Stores pid, mm, and tgid for each window. > + */ > +struct vas_user_win_ref { > + struct pid *pid; /* PID of owner */ > + struct pid *tgid; /* Thread group ID of owner */ > + struct mm_struct *mm; /* Linux process mm_struct */ > +}; > + > /* > * User space window operations used for powernv and powerVM > */ > @@ -59,6 +73,31 @@ struct vas_user_win_ops { > int (*close_win)(struct vas_window *); > }; > > +static inline void put_vas_user_win_ref(struct vas_user_win_ref *ref) > +{ > + /* Drop references to pid, tgid, and mm */ > + put_pid(ref->pid); > + put_pid(ref->tgid); > + if (ref->mm) > + mmdrop(ref->mm); > +} > + > +static inline void vas_user_win_add_mm_context(struct vas_user_win_ref *ref) > +{ > + mm_context_add_vas_window(ref->mm); > + /* > + * Even a process that has no foreign real address mapping can > + * use an unpaired COPY instruction (to no real effect). Issue > + * CP_ABORT to clear any pending COPY and prevent a covert > + * channel. > + * > + * __switch_to() will issue CP_ABORT on future context switches > + * if process / thread has any open VAS window (Use > + * current->mm->context.vas_windows). > + */ > + asm volatile(PPC_CP_ABORT); > +} > + > /* > * Receive window attributes specified by the (in-kernel) owner of window. > */ > @@ -190,4 +229,5 @@ int vas_register_coproc_api(struct module *mod, enum vas_cop_type cop_type, > const struct vas_user_win_ops *vops); > void vas_unregister_coproc_api(void); > > +int get_vas_user_win_ref(struct vas_user_win_ref *task_ref); > #endif /* __ASM_POWERPC_VAS_H */ > diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c > index 7cfc4b435ae8..1d7d3273d34b 100644 > --- a/arch/powerpc/platforms/book3s/vas-api.c > +++ b/arch/powerpc/platforms/book3s/vas-api.c > @@ -55,6 +55,45 @@ static char *coproc_devnode(struct device *dev, umode_t *mode) > return kasprintf(GFP_KERNEL, "crypto/%s", dev_name(dev)); > } > > +/* > + * Take reference to pid and mm > + */ > +int get_vas_user_win_ref(struct vas_user_win_ref *task_ref) > +{ > + /* > + * Window opened by a child thread may not be closed when > + * it exits. So take reference to its pid and release it > + * when the window is free by parent thread. > + * Acquire a reference to the task's pid to make sure > + * pid will not be re-used - needed only for multithread > + * applications. > + */ > + task_ref->pid = get_task_pid(current, PIDTYPE_PID); > + /* > + * Acquire a reference to the task's mm. > + */ > + task_ref->mm = get_task_mm(current); > + if (!task_ref->mm) { > + put_pid(task_ref->pid); > + pr_err("VAS: pid(%d): mm_struct is not found\n", > + current->pid); > + return -EPERM; > + } > + > + mmgrab(task_ref->mm); > + mmput(task_ref->mm); > + /* > + * Process closes window during exit. In the case of > + * multithread application, the child thread can open > + * window and can exit without closing it. So takes tgid > + * reference until window closed to make sure tgid is not > + * reused. > + */ > + task_ref->tgid = find_get_pid(task_tgid_vnr(current)); > + > + return 0; > +} > + > static int coproc_open(struct inode *inode, struct file *fp) > { > struct coproc_instance *cp_inst; > diff --git a/arch/powerpc/platforms/powernv/vas-fault.c b/arch/powerpc/platforms/powernv/vas-fault.c > index 3d21fce254b7..ac3a71ec3bd5 100644 > --- a/arch/powerpc/platforms/powernv/vas-fault.c > +++ b/arch/powerpc/platforms/powernv/vas-fault.c > @@ -73,7 +73,7 @@ static void update_csb(struct vas_window *window, > * NX user space windows can not be opened for task->mm=NULL > * and faults will not be generated for kernel requests. > */ > - if (WARN_ON_ONCE(!window->mm || !window->user_win)) > + if (WARN_ON_ONCE(!window->task_ref.mm || !window->user_win)) > return; > > csb_addr = (void __user *)be64_to_cpu(crb->csb_addr); > @@ -92,7 +92,7 @@ static void update_csb(struct vas_window *window, > csb.address = crb->stamp.nx.fault_storage_addr; > csb.flags = 0; > > - pid = window->pid; > + pid = window->task_ref.pid; > tsk = get_pid_task(pid, PIDTYPE_PID); > /* > * Process closes send window after all pending NX requests are > @@ -111,7 +111,7 @@ static void update_csb(struct vas_window *window, > * a window and exits without closing it. > */ > if (!tsk) { > - pid = window->tgid; > + pid = window->task_ref.tgid; > tsk = get_pid_task(pid, PIDTYPE_PID); > /* > * Parent thread (tgid) will be closing window when it > @@ -127,7 +127,7 @@ static void update_csb(struct vas_window *window, > return; > } > > - kthread_use_mm(window->mm); > + kthread_use_mm(window->task_ref.mm); > rc = copy_to_user(csb_addr, &csb, sizeof(csb)); > /* > * User space polls on csb.flags (first byte). So add barrier > @@ -139,7 +139,7 @@ static void update_csb(struct vas_window *window, > smp_mb(); > rc = copy_to_user(csb_addr, &csb, sizeof(u8)); > } > - kthread_unuse_mm(window->mm); > + kthread_unuse_mm(window->task_ref.mm); > put_task_struct(tsk); > > /* Success */ > diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c > index 5162e95c4090..4222c9bdb8fe 100644 > --- a/arch/powerpc/platforms/powernv/vas-window.c > +++ b/arch/powerpc/platforms/powernv/vas-window.c > @@ -1065,51 +1065,11 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop, > rc = -ENODEV; > goto free_window; > } > - > - /* > - * Window opened by a child thread may not be closed when > - * it exits. So take reference to its pid and release it > - * when the window is free by parent thread. > - * Acquire a reference to the task's pid to make sure > - * pid will not be re-used - needed only for multithread > - * applications. > - */ > - txwin->pid = get_task_pid(current, PIDTYPE_PID); > - /* > - * Acquire a reference to the task's mm. > - */ > - txwin->mm = get_task_mm(current); > - > - if (!txwin->mm) { > - put_pid(txwin->pid); > - pr_err("VAS: pid(%d): mm_struct is not found\n", > - current->pid); > - rc = -EPERM; > + rc = get_vas_user_win_ref(&txwin->task_ref); > + if (rc) > goto free_window; > - } > > - mmgrab(txwin->mm); > - mmput(txwin->mm); > - mm_context_add_vas_window(txwin->mm); > - /* > - * Process closes window during exit. In the case of > - * multithread application, the child thread can open > - * window and can exit without closing it. so takes tgid > - * reference until window closed to make sure tgid is not > - * reused. > - */ > - txwin->tgid = find_get_pid(task_tgid_vnr(current)); > - /* > - * Even a process that has no foreign real address mapping can > - * use an unpaired COPY instruction (to no real effect). Issue > - * CP_ABORT to clear any pending COPY and prevent a covert > - * channel. > - * > - * __switch_to() will issue CP_ABORT on future context switches > - * if process / thread has any open VAS window (Use > - * current->mm->context.vas_windows). > - */ > - asm volatile(PPC_CP_ABORT); > + vas_user_win_add_mm_context(&txwin->task_ref); > } > > set_vinst_win(vinst, txwin); > @@ -1340,13 +1300,8 @@ int vas_win_close(struct vas_window *window) > /* if send window, drop reference to matching receive window */ > if (window->tx_win) { > if (window->user_win) { > - /* Drop references to pid. tgid and mm */ > - put_pid(window->pid); > - put_pid(window->tgid); > - if (window->mm) { > - mm_context_remove_vas_window(window->mm); > - mmdrop(window->mm); > - } > + put_vas_user_win_ref(&window->task_ref); > + mm_context_remove_vas_window(window->task_ref.mm); > } > put_rx_win(window->rxwin); > } > diff --git a/arch/powerpc/platforms/powernv/vas.h b/arch/powerpc/platforms/powernv/vas.h > index c7db3190baca..f354dd5c51bd 100644 > --- a/arch/powerpc/platforms/powernv/vas.h > +++ b/arch/powerpc/platforms/powernv/vas.h > @@ -357,11 +357,9 @@ struct vas_window { > bool user_win; /* True if user space window */ > void *hvwc_map; /* HV window context */ > void *uwc_map; /* OS/User window context */ > - struct pid *pid; /* Linux process id of owner */ > - struct pid *tgid; /* Thread group ID of owner */ > - struct mm_struct *mm; /* Linux process mm_struct */ > int wcreds_max; /* Window credits */ > > + struct vas_user_win_ref task_ref; > char *dbgname; > struct dentry *dbgdir; > > @@ -443,7 +441,7 @@ extern void vas_win_paste_addr(struct vas_window *window, u64 *addr, > > static inline int vas_window_pid(struct vas_window *window) > { > - return pid_vnr(window->pid); > + return pid_vnr(window->task_ref.pid); > } > > static inline void vas_log_write(struct vas_window *win, char *name, > -- > 2.18.2 > > >