Messages in this thread | | | Date | Mon, 4 Dec 2017 23:51:00 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [patch 47/60] x86/ldt: Map LDT entries into fixmap |
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On Mon, 4 Dec 2017, Andy Lutomirski wrote:
> On Mon, Dec 4, 2017 at 6:07 AM, Thomas Gleixner <tglx@linutronix.de> wrote: > > From: Thomas Gleixner <tglx@linutronix.de> > > > > LDT is not really commonly used on 64bit so the overhead of populating the > > fixmap entries on context switch for the rare LDT syscall users is a > > reasonable trade off vs. having extra dynamically managed mapping space per > > process. > > > > Hmm, I wonder just how slow this is. It might be okay. It's > certainly not the way I imagined it working.
I know, it was the laziest way I could come up with. The only nasty thing here is that __set_fixmap() does a tlb flush which is pointless as that happens anyway. On my todo list was a noflush variant for set_fixmap along with a variant which takes a whole range. That would simplify other places as well. Though with the plan to map that stuff to a different place we actually can avoid the weirdness of fixmaps
Thanks,
tglx
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