On 14.12.25 09:05, Ingo Molnar wrote:
* Juergen Gross <[email protected]> wrote:While looking at paravirt cleanups I stumbled over slow_down_io() and the related REALLY_SLOW_IO define. Especially REALLY_SLOW_IO is a mess, which is proven by 2 completely wrong use cases. Do several cleanups, resulting in a deletion of REALLY_SLOW_IO and the io_delay() paravirt function hook. Patches 2 and 3 are not changing any functionality, but maybe they should? As the potential bug has been present for more than a decade now, I went with just deleting the useless "#define REALLY_SLOW_IO". The alternative would be to do something similar as in patch 5. Juergen Gross (5): x86/paravirt: Replace io_delay() hook with a bool hwmon/lm78: Drop REALLY_SLOW_IO setting hwmon/w83781d: Drop REALLY_SLOW_IO setting block/floppy: Don't use REALLY_SLOW_IO for delays x86/io: Remove REALLY_SLOW_IO handling arch/x86/include/asm/floppy.h | 27 ++++++++++++++++++++++----- arch/x86/include/asm/io.h | 12 +++++------- arch/x86/include/asm/paravirt.h | 11 +---------- arch/x86/include/asm/paravirt_types.h | 3 +-- arch/x86/kernel/cpu/vmware.c | 2 +- arch/x86/kernel/kvm.c | 8 +------- arch/x86/kernel/paravirt.c | 3 +-- arch/x86/xen/enlighten_pv.c | 6 +----- drivers/block/floppy.c | 2 -- drivers/hwmon/lm78.c | 5 +++-- drivers/hwmon/w83781d.c | 5 +++-- 11 files changed, 39 insertions(+), 45 deletions(-)I think we should get rid of *all* io_delay hacks, they might have been relevant in the days of i386 systems, but we don't even support i386 CPUs anymore. Should it cause any regressions, it's easy to bisect to. There's been enough changes around all these facilities that the original timings are probably way off already, so we've just been cargo-cult porting these to newer kernels essentially.
Fine with me. Which path to removal of io_delay would you (and others) prefer? 1. Ripping it out immediately. 2. Hiding it behind a default-off config option for a few kernel versions before removing it. 3. Using CONFIG_IO_DELAY_NONE as the default io_delay_type before ripping it out. 4. Using CONFIG_IO_DELAY_NONE as the default io_delay_type before hiding it behind a default-off config option, then rip it out later. In cases 2-4 I'd still like to have patch 1 of my series applied, as it will make paravirt rework easier. Juergen
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