From ecc7e37d4dadd16f6be125ca496feccd05454da4 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 11 Nov 2019 23:03:20 +0100 Subject: x86/io: Speedup schedule out of I/O bitmap user There is no requirement to update the TSS I/O bitmap when a thread using it is scheduled out and the incoming thread does not use it. For the permission check based on the TSS I/O bitmap the CPU calculates the memory location of the I/O bitmap by the address of the TSS and the io_bitmap_base member of the tss_struct. The easiest way to invalidate the I/O bitmap is to switch the offset to an address outside of the TSS limit. If an I/O instruction is issued from user space the TSS limit causes #GP to be raised in the same was as valid I/O bitmap with all bits set to 1 would do. This removes the extra work when an I/O bitmap using task is scheduled out and puts the burden on the rare I/O bitmap users when they are scheduled in. Signed-off-by: Thomas Gleixner --- arch/x86/kernel/doublefault.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/kernel/doublefault.c') diff --git a/arch/x86/kernel/doublefault.c b/arch/x86/kernel/doublefault.c index 0b8cedb20d6d..cedb07d0909c 100644 --- a/arch/x86/kernel/doublefault.c +++ b/arch/x86/kernel/doublefault.c @@ -54,7 +54,7 @@ struct x86_hw_tss doublefault_tss __cacheline_aligned = { .sp0 = STACK_START, .ss0 = __KERNEL_DS, .ldt = 0, - .io_bitmap_base = INVALID_IO_BITMAP_OFFSET, + .io_bitmap_base = IO_BITMAP_OFFSET_INVALID, .ip = (unsigned long) doublefault_fn, /* 0x2 bit is always set */ -- cgit v1.2.3