[Linux-ia64] SMP TLB flushes

[Linux-ia64] SMP TLB flushes

[Manfred Spraul]

Is it correct that the SMP part of the SMP flushing code is still
missing? I'm just noisy and I don't understand yet how the ia64 cpu is
supposed to perform tlb flushes.

* ptc.g only gets the address and the size as parameters, but not a
region id. What if cpu 1 (running kswapd, arbitrary thread context)
wants to flush a page from another thread, and that thread is running on
cpu 2?

* could you add a big warning to start_lazy_tlb [kernel/exit.c] that the
function is unsafe?
Both ppc and ia64 scan the task list and assume that they can find each
mm_struct. If someone actually uses start_lazy_tlb, then that would be
incorrect.

Btw, the i386 tlb flush contained a single instruction race (read x,
write y instead of write y, read x) and this was enough for corruptions
- I overlooked one problem with concurrent tlb flushes and thread
switches.

Please cc me, I'm not subscribed to the list.

--
	Manfred

RE: [Linux-ia64] SMP TLB flushes

[Stephan.Zeisset]

As for the ptc.g, the region id comes from the region register that
is selected through bits [63:61] of the address.

-----Original Message-----
From: Manfred Spraul [mailto:manfred@colorfullife.com]
Sent: Thursday, August 31, 2000 10:57 AM
To: linux-ia64@linuxia64.org
Subject: [Linux-ia64] SMP TLB flushes


Is it correct that the SMP part of the SMP flushing code is still
missing? I'm just noisy and I don't understand yet how the ia64 cpu is
supposed to perform tlb flushes.

* ptc.g only gets the address and the size as parameters, but not a
region id. What if cpu 1 (running kswapd, arbitrary thread context)
wants to flush a page from another thread, and that thread is running on
cpu 2?

* could you add a big warning to start_lazy_tlb [kernel/exit.c] that the
function is unsafe?
Both ppc and ia64 scan the task list and assume that they can find each
mm_struct. If someone actually uses start_lazy_tlb, then that would be
incorrect.

Btw, the i386 tlb flush contained a single instruction race (read x,
write y instead of write y, read x) and this was enough for corruptions
- I overlooked one problem with concurrent tlb flushes and thread
switches.

Please cc me, I'm not subscribed to the list.

--
	Manfred

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Re: [Linux-ia64] SMP TLB flushes

[David Mosberger]

>>>>> On Thu, 31 Aug 2000 19:57:11 +0200, Manfred Spraul <manfred@colorfullife.com> said:

  Manfred> * could you add a big warning to start_lazy_tlb
  Manfred> [kernel/exit.c] that the function is unsafe?  Both ppc and
  Manfred> ia64 scan the task list and assume that they can find each
  Manfred> mm_struct. If someone actually uses start_lazy_tlb, then
  Manfred> that would be incorrect.

Why are you asking on the IA-64 list for this change?  It's in a
platform-independent file so it's up to Linus to decide what to do
with that function.  It's presently unused and if it's not safe, why
not get rid of it?

	--david

RE: [Linux-ia64] SMP TLB flushes

[Rao, Goutham]

Hi,
ptc.g gets RID from bits 63:61 of the address used in the purge instruction.

Thanks
Goutham

-----Original Message-----
From: Manfred Spraul [mailto:manfred@colorfullife.com]
Sent: Thursday, August 31, 2000 10:57 AM
To: linux-ia64@linuxia64.org
Subject: [Linux-ia64] SMP TLB flushes


Is it correct that the SMP part of the SMP flushing code is still
missing? I'm just noisy and I don't understand yet how the ia64 cpu is
supposed to perform tlb flushes.

* ptc.g only gets the address and the size as parameters, but not a
region id. What if cpu 1 (running kswapd, arbitrary thread context)
wants to flush a page from another thread, and that thread is running on
cpu 2?

* could you add a big warning to start_lazy_tlb [kernel/exit.c] that the
function is unsafe?
Both ppc and ia64 scan the task list and assume that they can find each
mm_struct. If someone actually uses start_lazy_tlb, then that would be
incorrect.

Btw, the i386 tlb flush contained a single instruction race (read x,
write y instead of write y, read x) and this was enough for corruptions
- I overlooked one problem with concurrent tlb flushes and thread
switches.

Please cc me, I'm not subscribed to the list.

--
	Manfred

_______________________________________________
Linux-IA64 mailing list
Linux-IA64@linuxia64.org
http://lists.linuxia64.org/lists/listinfo/linux-ia64

Re: [Linux-ia64] SMP TLB flushes

[Manfred Spraul]

Stephan.Zeisset@intel.com wrote:
> 
> As for the ptc.g, the region id comes from the region register that
> is selected through bits [63:61] of the address.
> 

That means flush_tlb_range on SMP should

* acquire ptcg_lock
* change the region register to mm->...
* ptc.g
* restore the region register from current->active_mm->...
* release the spinlock.


Thanks for your answer,

	Manfred