On Sun, Sep 20, 2020 at 10:42 AM Linus Torvalds
wrote:
>
> Yeah, that looks much easier to explain. Ack.
Btw, one thing that might be a good idea at least initially is to add
a check for p->kmap_ctrl.idx being zero at fork, exit and maybe
syscall return time (but that last one may be too
On Sun, Sep 20, 2020 at 10:40 AM Thomas Gleixner wrote:
>
> I think the more obvious solution is to split the whole exercise:
>
> schedule()
> prepare_switch()
> unmap()
>
> switch_to()
>
> finish_switch()
> map()
Yeah, that looks much easier to explain. Ack.
On Sun, Sep 20 2020 at 09:57, Linus Torvalds wrote:
> On Sun, Sep 20, 2020 at 1:49 AM Thomas Gleixner wrote:
> Btw, looking at the stack code, Ithink your new implementation of it
> is a bit scary:
>
>static inline int kmap_atomic_idx_push(void)
>{
> - int idx =
On Sun, Sep 20 2020 at 10:23, Daniel Vetter wrote:
> On Sun, Sep 20, 2020 at 08:23:26AM +0200, Thomas Gleixner wrote:
>> On Sat, Sep 19 2020 at 12:37, Daniel Vetter wrote:
>> > On Sat, Sep 19, 2020 at 12:35 PM Daniel Vetter wrote:
>> >> I think it should be the case, but I want to double check:
On Sun, Sep 20, 2020 at 1:49 AM Thomas Gleixner wrote:
>
> Actually most usage sites of kmap atomic do not need page faults to be
> disabled at all.
Right. I think the pagefault disabling has (almost) nothing at all to
do with the kmap() itself - it comes from the "atomic" part, not the
"kmap"
On Sun, Sep 20 2020 at 08:41, Thomas Gleixner wrote:
> On Sat, Sep 19 2020 at 10:18, Linus Torvalds wrote:
>> Maybe I've missed something. Is it because the new interface still
>> does "pagefault_disable()" perhaps?
>>
>> But does it even need the pagefault_disable() at all? Yes, the
>> *atomic*
On Sun, Sep 20, 2020 at 08:23:26AM +0200, Thomas Gleixner wrote:
> On Sat, Sep 19 2020 at 12:37, Daniel Vetter wrote:
> > On Sat, Sep 19, 2020 at 12:35 PM Daniel Vetter wrote:
> >> I think it should be the case, but I want to double check: Will
> >> copy_*_user be allowed within a kmap_temporary
On Sat, Sep 19 2020 at 10:18, Linus Torvalds wrote:
> On Sat, Sep 19, 2020 at 2:50 AM Thomas Gleixner wrote:
>>
>> this provides a preemptible variant of kmap_atomic & related
>> interfaces. This is achieved by:
>
> Ack. This looks really nice, even apart from the new capability.
>
> The only
On Sat, Sep 19 2020 at 12:37, Daniel Vetter wrote:
> On Sat, Sep 19, 2020 at 12:35 PM Daniel Vetter wrote:
>> I think it should be the case, but I want to double check: Will
>> copy_*_user be allowed within a kmap_temporary section? This would
>> allow us to ditch an absolute pile of slowpaths.
>
