| |
|
 |
|
 |
|
|
|
| |
|
|
xen-devel
[Xen-devel] Re: Question about x86/mm/gup.c's use of disabled interrupts
Avi Kivity wrote:
Hm, awkward if flush_tlb_others doesn't IPI...
How can it avoid flushing the tlb on cpu [01]? It's it's
gup_fast()ing a pte, it may as well load it into the tlb.
xen_flush_tlb_others uses a hypercall rather than an IPI, so none of the
logic which depends on there being an IPI will work.
Simplest fix is to make gup_get_pte() a pvop, but that does seem like
putting a red flag in front of an inner-loop hotspot, or something...
The per-cpu tlb-flush exclusion flag might really be the way to go.
I don't see how it will work, without changing Xen to look at the flag?
local_irq_disable() is used here to lock out a remote cpu, I don't see
why deferring the flush helps.
Well, no, not deferring. Making xen_flush_tlb_others() spin waiting for
"doing_gup" to clear on the target cpu. Or add an explicit notion of a
"pte update barrier" rather than implicitly relying on the tlb IPI
(which is extremely convenient when available...).
J
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
|
|
| |
|
Home