kernel.git/arch/um/kernel/irq.c, branch linux-5.13.y

um: time-travel: rework interrupt handling in ext mode

2021-02-12T20:24:27Z

In external time-travel mode, where time is controlled via the controller application socket, interrupt handling is a little tricky. For example on virtio, the following happens: * we receive a message (that requires an ACK) on the vhost-user socket * we add a time-travel event to handle the interrupt (this causes communication on the time socket) * we ACK the original vhost-user message * we then handle the interrupt once the event is triggered This protocol ensures that the sender of the interrupt only continues to run in the simulation when the time-travel event has been added. So far, this was only done in the virtio driver, but it was actually wrong, because only virtqueue interrupts were handled this way, and config change interrupts were handled immediately. Additionally, the messages were actually handled in the real Linux interrupt handler, but Linux interrupt handlers are part of the simulation and shouldn't run while there's no time event. To really do this properly and only handle all kinds of interrupts in the time-travel event when we are scheduled to run in the simulation, rework this to plug in to the lower interrupt layers in UML directly: Add a um_request_irq_tt() function that let's a time-travel aware driver request an interrupt with an additional timetravel_handler() that is called outside of the context of the simulation, to handle the message only. It then adds an event to the time-travel calendar if necessary, and no "real" Linux code runs outside of the time simulation. This also hooks in with suspend/resume properly now, since this new timetravel_handler() can run while Linux is suspended and interrupts are disabled, and decide to wake up (or not) the system based on the message it received. Importantly in this case, it ACKs the message before the system even resumes and interrupts are re-enabled, thus allowing the simulation to progress properly. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: irq/sigio: Support suspend/resume handling of workaround IRQs

2020-12-13T21:42:01Z

If the sigio workaround needed to be applied to a file descriptor, set_irq_wake() wouldn't work for it since it would get polled by the thread instead of causing SIGIO, and thus could never really cause a wakeup, since the thread notification FD wasn't marked as being able to wake up the system. Fix this by marking the thread's notification FD explicitly as a wake source FD, i.e. not suppressing SIGIO for it in suspend. In order to not cause spurious wakeups, we then need to remove all FDs that shouldn't wake up the system from the polling thread. In order to do this, add unlocked versions of ignore_sigio_fd() and add_sigio_fd() (nothing else is happening in suspend, so this is fine), and also modify ignore_sigio_fd() to return -ENOENT if the FD wasn't originally in there. This doesn't matter because nothing else currently checks the return value, but the irq code needs to know which ones to restore the workaround for. All told, this lets us use a timerfd for the RTC clock in the next patch, which doesn't send SIGIO. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: Support suspend to RAM

2020-12-13T21:22:49Z

With all the previous bits in place, we can now also support suspend to RAM, in the sense that everything is suspended, not just most, including userspace, processes like in s2idle. Since um_idle_sleep() now waits forever, we can simply call that to "suspend" the system. As before, you can wake it up using SIGUSR1 since we're just in a pause() call that only needs to return. In order to implement selective resume from certain devices, and not have any arbitrary device interrupt wake up, suspend interrupts by removing SIGIO notification (O_ASYNC) from all the FDs that are not supposed to wake up the system. However, swap out the handler so we don't actually handle the SIGIO as an interrupt. Since we're in pause(), the mere act of receiving SIGIO wakes us up, and then after things have been restored enough, re-set O_ASYNC for all previously suspended FDs, reinstall the proper SIGIO handler, and send SIGIO to self to process anything that might now be pending. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: Simplify IRQ handling code

2020-12-13T21:22:33Z

Reduce dynamic allocations (and thereby cache misses) by simply embedding the registration data for IRQs in the irq_entry, we never supported these being really dynamic anyway as only one was ever allowed ("Trying to reregister ..."). Lockless behaviour is preserved by removing the FD from the poll set appropriately, but we use reg->events to indicate whether or not this entry is used, rather than dynamically allocating them. Also port the list of IRQ entries to list_head instead of the current open-coded singly-linked list implementation, just for sanity. Signed-off-by: Johannes Berg Acked-By: Anton Ivanov Signed-off-by: Richard Weinberger

um: Remove IRQ_NONE type

2020-12-13T21:22:29Z

We don't actually use this in um_request_irq(), so it can never be assigned. It's also not clear what that would be useful for, so just remove it. This results in quite a number of cleanups, all the way to removing the "SIGIO on close" startup check, since the data it assigns (pty_close_sigio) is not used anymore. While at it, also make this an enum so we get a minimum of type checking, and remove the IRQ_NONE hack in virtio since we now no longer have the name twice. Acked-By: Anton Ivanov Signed-off-by: Johannes Berg Acked-By: Anton Ivanov Signed-off-by: Richard Weinberger

um: irq: Reduce irq_reg allocation

2020-12-13T21:22:23Z

We don't need an array of 4 entries to capture three and the name 'MAX_IRQ_TYPE' really gets confusing as well. Remove it and add a correct NUM_IRQ_TYPES, and use that correctly. Signed-off-by: Johannes Berg Acked-By: Anton Ivanov Signed-off-by: Richard Weinberger

um: irq: Clean up and rename struct irq_fd

2020-12-13T21:22:19Z

This really shouldn't be called "irq_fd" since it doesn't carry an fd. Well, it used to, apparently, but that struct member is unused. Rename it to "irq_reg" since it more accurately reflects a registered interrupt, and remove the unused 'next' and 'fd' members from the struct as well. While at it, also move it to the implementation, it's not used anywhere else, and the header file is shared with the userspace components. Acked-By: Anton Ivanov Signed-off-by: Johannes Berg Acked-By: Anton Ivanov Signed-off-by: Richard Weinberger

um: Clean up alarm IRQ chip name

2020-12-13T21:22:15Z

We don't use "SIGVTALRM", it's just SIGALRM. Clean up the naming. While at it, fix the comment's grammar. Acked-By: Anton Ivanov Signed-off-by: Johannes Berg Acked-By: Anton Ivanov Signed-off-by: Richard Weinberger

um: Support dynamic IRQ allocation

2020-12-13T21:22:08Z

It's cumbersome and error-prone to keep adding fixed IRQ numbers, and for proper device wakeup support for the virtio/vhost-user support we need to have different IRQs for each device. Even if in theory two IRQs (with and without wake) might be sufficient, it's much easier to reason about it when we have dynamic number assignment. It also makes it easier to add new devices that may dynamically exist or depending on the configuration, etc. Add support for this, up to 64 IRQs (the same limit as epoll FDs we have right now). Since it's not easy to port all the existing places to dynamic allocation (some data is statically initialized) keep the low numbers are reserved for the existing hard-coded IRQ numbers. Acked-By: Anton Ivanov Signed-off-by: Johannes Berg Acked-By: Anton Ivanov Signed-off-by: Richard Weinberger

um: irq: Fix LAST_IRQ usage in init_IRQ()

2019-09-16T06:38:58Z

LAST_IRQ was used incorrectly in init_IRQ. Commit 09ccf0364ca3 forgot to update the for loop. Fix this. Fixes: 49da7e64f33e ("High Performance UML Vector Network Driver") Fixes: 09ccf0364ca3 ("um: Fix off by one error in IRQ enumeration") Signed-off-by: Erel Geron Signed-off-by: Johannes Berg Acked-by: Anton Ivanov Signed-off-by: Richard Weinberger