Re: [PATCH 3/25][V3] irq_flags / halt routines
From: Glauber de Oliveira Costa
Date: Wed Aug 15 2007 - 12:22:12 EST
Andi Kleen escreveu:
On Wed, Aug 15, 2007 at 12:09:42PM -0300, Glauber de Oliveira Costa wrote:
Again, this is the code of such function:
static inline int raw_irqs_disabled_flags(unsigned long flags)
{
return !(flags & X86_EFLAGS_IF);
}
so all it is doing is getting a parameter (flags), and bitmasking it. It
is not talking to any hypervisor. I can't see your point. Unless you are
arguing that it _should_ be talking to a hypervisor. Is that your point?
vSMP is a hypervisor based architecture. For some reason that is not
100% clear to me, but Kiran or Shai can probably explain, it needs this
additional bit in EFLAGS when interrupts are disabled. That gives
it some hints and then it goes somehow faster. That is clearly
paravirtualization.
Since paravirtops is designed to handle such hooks cleanly I request
that you move vSMP over to it or work with the vSMP maintainers to
do that. Otherwise we have two different ways to do paravirtualization
which is wrong.
Thanks for the explanation, Andi. I understand it much better now, and
agree with you.
As alternatives what we have now, we can either keep the paravirt_ops as
it is now for the native case, just hooking the vsmp functions in place
of the normal one, (there are just three ops anyway), refill the
paravirt_ops entirely in somewhere like vsmp.c, or similar (or maybe
even assigning paravirt_ops.fn = vsmp_fn on the fly, but early enough).
Maybe we could even make VSMP depend on PARAVIRT, to make it sure it is
completely a paravirt client.
But as you could see, my knowledge of vsmp does not go that far, and I
would really like to have input from the vsmp guys prior to touch
anything here.
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