Messages in this thread Patch in this message | | | Date | Thu, 01 Aug 2019 16:32:51 +0200 | From | Thomas Gleixner <> | Subject | [patch 1/5] tracehook: Provide TIF_NOTIFY_RESUME handling for KVM |
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TIF_NOTITY_RESUME is evaluated on return to user space along with other TIF flags.
>From the kernels point of view a VMENTER is more or less equivalent to return to user space which means that at least a subset of TIF flags needs to be evaluated and handled.
Currently KVM handles only TIF_SIGPENDING and TIF_NEED_RESCHED, but TIF_NOTIFY_RESUME is ignored. So pending task_work etc, is completely ignored until the vCPU thread actually goes all the way back into userspace/qemu.
Provide notify_resume_pending() and tracehook_handle_notify_resume() so this can be handled similar to SIGPENDING.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Oleg Nesterov <oleg@redhat.com> --- include/linux/tracehook.h | 15 +++++++++++++++ kernel/task_work.c | 19 +++++++++++++++++++ 2 files changed, 34 insertions(+)
--- a/include/linux/tracehook.h +++ b/include/linux/tracehook.h @@ -163,6 +163,21 @@ static inline void set_notify_resume(str #endif } +#ifdef CONFIG_HAVE_ARCH_TRACEHOOK +/** + * notify_resume_pending - Check whether current has TIF_NOTIFY_RESUME set + */ +static inline bool notify_resume_pending(void) +{ + return test_thread_flag(TIF_NOTIFY_RESUME); +} + +void tracehook_handle_notify_resume(void); +#else +static inline bool notify_resume_pending(void) { return false; } +static inline void tracehook_handle_notify_resume(void) { } +#endif + /** * tracehook_notify_resume - report when about to return to user mode * @regs: user-mode registers of @current task --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -116,3 +116,22 @@ void task_work_run(void) } while (work); } } + +#ifdef CONFIG_HAVE_ARCH_TRACEHOOK +/** + * tracehook_handle_notify_resume - Notify resume handling for virt + * + * Called with interrupts and preemption enabled from VMENTER/EXIT. + */ +void tracehook_handle_notify_resume(void) +{ + local_irq_disable(); + while (test_and_clear_thread_flag(TIF_NOTIFY_RESUME)) { + local_irq_enable(); + tracehook_notify_resume(NULL); + local_irq_disable(); + } + local_irq_enable(); +} +EXPORT_SYMBOL_GPL(tracehook_handle_notify_resume); +#endif
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