Re: [V3 PATCH 03/16] powerpc/vas: Create take/drop task reference functions
On Mon, 2021-05-10 at 15:28 +1000, Nicholas Piggin wrote:
> Excerpts from Haren Myneni's message of April 18, 2021 7:03 am:
> > Take task reference 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
> > ---
> > arch/powerpc/include/asm/vas.h | 20
> > arch/powerpc/platforms/book3s/vas-api.c | 51
> > ++
> > arch/powerpc/platforms/powernv/vas-fault.c | 10 ++--
> > arch/powerpc/platforms/powernv/vas-window.c | 57 ++---
> >
> > arch/powerpc/platforms/powernv/vas.h| 6 +--
> > 5 files changed, 83 insertions(+), 61 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/vas.h
> > b/arch/powerpc/include/asm/vas.h
> > index 6bbade60d8f4..2daaa1a2a9a9 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
> > +#include
> > +#include
> > #include
> >
> >
> > @@ -60,6 +63,22 @@ struct vas_user_win_ops {
> > int (*close_win)(void *);
> > };
> >
> > +struct vas_win_task {
> > + struct pid *pid;/* Thread group ID of owner */
> > + struct pid *tgid; /* Linux process mm_struct */
> > + struct mm_struct *mm; /* Linux process mm_struct */
> > +};
>
> Looks okay, happy with struct vas_win_task? (and vas_user_win_ops)?
>
> I'd be happier to have everything related to vas windows prefixed
> with
> vas_window_ consistently, and have _user be present always for
> userspace
> windows, but you have to read and type it.
I will change to vas_window_task and vas_user_window_ops. struct
vas_window is common for both kernel and user space window, but struct
vas_window_task is needed only for user space.
>
> > +
> > +static inline void vas_drop_reference_task(struct vas_win_task
> > *task)
>
> This is not dropping a reference task, but a task reference. And
> it's
> not really a task reference as far as Linux understands, but a
> reference on pid (not task) and mm related to an open vas window. And
> specifically a user window (with corresponding vas_user_win_ops).
Yes get and put references to pid and mm. Hence mentioned
reference_task to reflect for both pid and mm. Would you prefer
vas_put_reference_pid_mm()?
>
> Could it be called a 'struct vas_window_user_ref' instead?
To support LPM and DLPAR, plannig to add VMA (mapping address) in
struct vas_window_task. But I can change it to 'struct
vas_window_user_ref' instread of vas_window_task.
Thanks
Haren
>
> Thanks,
> Nick
>
> > +{
> > + /* Drop references to pid and mm */
> > + put_pid(task->pid);
> > + if (task->mm) {
> > + mm_context_remove_vas_window(task->mm);
> > + mmdrop(task->mm);
> > + }
Re: [V3 PATCH 03/16] powerpc/vas: Create take/drop task reference functions
Excerpts from Haren Myneni's message of April 18, 2021 7:03 am:
>
> Take task reference 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
> ---
> arch/powerpc/include/asm/vas.h | 20
> arch/powerpc/platforms/book3s/vas-api.c | 51 ++
> arch/powerpc/platforms/powernv/vas-fault.c | 10 ++--
> arch/powerpc/platforms/powernv/vas-window.c | 57 ++---
> arch/powerpc/platforms/powernv/vas.h| 6 +--
> 5 files changed, 83 insertions(+), 61 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
> index 6bbade60d8f4..2daaa1a2a9a9 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
> +#include
> +#include
> #include
>
>
> @@ -60,6 +63,22 @@ struct vas_user_win_ops {
> int (*close_win)(void *);
> };
>
> +struct vas_win_task {
> + struct pid *pid;/* Thread group ID of owner */
> + struct pid *tgid; /* Linux process mm_struct */
> + struct mm_struct *mm; /* Linux process mm_struct */
> +};
Looks okay, happy with struct vas_win_task? (and vas_user_win_ops)?
I'd be happier to have everything related to vas windows prefixed with
vas_window_ consistently, and have _user be present always for userspace
windows, but you have to read and type it.
> +
> +static inline void vas_drop_reference_task(struct vas_win_task *task)
This is not dropping a reference task, but a task reference. And it's
not really a task reference as far as Linux understands, but a
reference on pid (not task) and mm related to an open vas window. And
specifically a user window (with corresponding vas_user_win_ops).
Could it be called a 'struct vas_window_user_ref' instead?
Thanks,
Nick
> +{
> + /* Drop references to pid and mm */
> + put_pid(task->pid);
> + if (task->mm) {
> + mm_context_remove_vas_window(task->mm);
> + mmdrop(task->mm);
> + }
[V3 PATCH 03/16] powerpc/vas: Create take/drop task reference functions
Take task reference 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
---
arch/powerpc/include/asm/vas.h | 20
arch/powerpc/platforms/book3s/vas-api.c | 51 ++
arch/powerpc/platforms/powernv/vas-fault.c | 10 ++--
arch/powerpc/platforms/powernv/vas-window.c | 57 ++---
arch/powerpc/platforms/powernv/vas.h| 6 +--
5 files changed, 83 insertions(+), 61 deletions(-)
diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
index 6bbade60d8f4..2daaa1a2a9a9 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
+#include
+#include
#include
@@ -60,6 +63,22 @@ struct vas_user_win_ops {
int (*close_win)(void *);
};
+struct vas_win_task {
+ struct pid *pid;/* Thread group ID of owner */
+ struct pid *tgid; /* Linux process mm_struct */
+ struct mm_struct *mm; /* Linux process mm_struct */
+};
+
+static inline void vas_drop_reference_task(struct vas_win_task *task)
+{
+ /* Drop references to pid and mm */
+ put_pid(task->pid);
+ if (task->mm) {
+ mm_context_remove_vas_window(task->mm);
+ mmdrop(task->mm);
+ }
+}
+
/*
* Receive window attributes specified by the (in-kernel) owner of window.
*/
@@ -190,4 +209,5 @@ int vas_register_coproc_api(struct module *mod, enum
vas_cop_type cop_type,
struct vas_user_win_ops *vops);
void vas_unregister_coproc_api(void);
+int vas_reference_task(struct vas_win_task *vtask);
#endif /* __ASM_POWERPC_VAS_H */
diff --git a/arch/powerpc/platforms/book3s/vas-api.c
b/arch/powerpc/platforms/book3s/vas-api.c
index 05d7b99acf41..d98caa734154 100644
--- a/arch/powerpc/platforms/book3s/vas-api.c
+++ b/arch/powerpc/platforms/book3s/vas-api.c
@@ -60,6 +60,57 @@ 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 vas_reference_task(struct vas_win_task *vtask)
+{
+ /*
+* 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.
+*/
+ vtask->pid = get_task_pid(current, PIDTYPE_PID);
+ /*
+* Acquire a reference to the task's mm.
+*/
+ vtask->mm = get_task_mm(current);
+ if (!vtask->mm) {
+ put_pid(vtask->pid);
+ pr_err("VAS: pid(%d): mm_struct is not found\n",
+ current->pid);
+ return -EPERM;
+ }
+
+ mmgrab(vtask->mm);
+ mmput(vtask->mm);
+ mm_context_add_vas_window(vtask->mm);
+ /*
+* Process closes window during exit. In the case of
+* multithread application, the child thread can open
+* window and can exit without closing it. Expects parent
+* thread to use and close the window. So do not need
+* to take pid reference for parent thread.
+*/
+ vtask->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);
+
+ 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..a4835cb82c09 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.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
