3 Commits

Author	SHA1	Message	Date
Thomas Gleixner	22fe5b0439	x86/ioperm: Move TSS bitmap update to exit to user work ... There is no point to update the TSS bitmap for tasks which use I/O bitmaps on every context switch. It's enough to update it right before exiting to user space. That reduces the context switch bitmap handling to invalidating the io bitmap base offset in the TSS when the outgoing task has TIF_IO_BITMAP set. The invaldiation is done on purpose when a task with an IO bitmap switches out to prevent any possible leakage of an activated IO bitmap. It also removes the requirement to update the tasks bitmap atomically in ioperm(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de>	2019-11-16 11:24:03 +01:00
Thomas Gleixner	060aa16fdb	x86/ioperm: Add bitmap sequence number ... Add a globally unique sequence number which is incremented when ioperm() is changing the I/O bitmap of a task. Store the new sequence number in the io_bitmap structure and compare it with the sequence number of the I/O bitmap which was last loaded on a CPU. Only update the bitmap if the sequence is different. That should further reduce the overhead of I/O bitmap scheduling when there are only a few I/O bitmap users on the system. The 64bit sequence counter is sufficient. A wraparound of the sequence counter assuming an ioperm() call every nanosecond would require about 584 years of uptime. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>	2019-11-16 11:24:02 +01:00
Thomas Gleixner	577d5cd7e5	x86/ioperm: Move iobitmap data into a struct ... No point in having all the data in thread_struct, especially as upcoming changes add more. Make the bitmap in the new struct accessible as array of longs and as array of characters via a union, so both the bitmap functions and the update logic can avoid type casts. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>	2019-11-16 11:24:02 +01:00