From: Avi Kivity <avi@redhat.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Don Zickus <dzickus@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nick Piggin <npiggin@kernel.dk>,
Marcelo Tosatti <mtosatti@redhat.com>, KVM <kvm@vger.kernel.org>,
Andi Kleen <andi@firstfloor.org>,
Xen Devel <xen-devel@lists.xensource.com>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking
Date: Thu, 08 Sep 2011 10:51:26 +0300 [thread overview]
Message-ID: <4E6873FE.3040603@redhat.com> (raw)
In-Reply-To: <4E67C15B.3000408@goop.org>
On 09/07/2011 10:09 PM, Jeremy Fitzhardinge wrote:
> On 09/07/2011 10:41 AM, Avi Kivity wrote:
> >> Hm, I'm interested to know what you're thinking in more detail. Can you
> >> leave an NMI pending before you block in the same way you can with
> >> "sti;halt" with normal interrupts?
> >
> >
> > Nope. But you can do
> >
> > if (regs->rip in critical section)
> > regs->rip = after_halt;
> >
> > and effectively emulate it. The critical section is something like
> >
> > critical_section_start:
> > if (woken_up)
> > goto critical_section_end;
> > hlt
> > critical_section_end:
>
> Hm. It's a pity you have to deliver an actual interrupt to implement
> the kick though.
I don't think it's that expensive, especially compared to the
double-context-switch and vmexit of the spinner going to sleep. On AMD
we do have to take an extra vmexit (on IRET) though.
> >>
> >> I was thinking you might want to do something with monitor/mwait to
> >> implement the blocking/kick ops. (Handwave)
> >>
> >
> > monitor/mwait are incredibly expensive to virtualize since they
> > require write-protecting a page, IPIs flying everywhere and flushing
> > tlbs, not to mention my lovely hugepages being broken up mercilessly.
>
> Or what about a futex-like hypercall?
>
Well we could have a specialized sleep/wakeup hypercall pair like Xen,
but I'd like to avoid it if at all possible.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2011-09-08 7:51 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-02 0:54 [PATCH 00/13] [PATCH RFC] Paravirtualized ticketlocks Jeremy Fitzhardinge
2011-09-02 0:54 ` [PATCH 01/13] x86/spinlocks: replace pv spinlocks with pv ticketlocks Jeremy Fitzhardinge
2011-09-02 0:54 ` [PATCH 02/13] x86/ticketlock: collapse a layer of functions Jeremy Fitzhardinge
2011-09-02 0:54 ` [PATCH 03/13] xen/pvticketlock: Xen implementation for PV ticket locks Jeremy Fitzhardinge
2011-09-02 0:54 ` [PATCH 04/13] x86/pvticketlock: use callee-save for lock_spinning Jeremy Fitzhardinge
2011-09-02 0:54 ` [PATCH 05/13] x86/ticketlocks: when paravirtualizing ticket locks, increment by 2 Jeremy Fitzhardinge
2011-09-02 0:54 ` [PATCH 06/13] x86/ticketlock: add slowpath logic Jeremy Fitzhardinge
2011-09-02 18:46 ` Eric Northup
2011-09-02 19:32 ` Jeremy Fitzhardinge
2011-09-02 0:55 ` [PATCH 07/13] x86/ticketlocks: tidy up __ticket_unlock_kick() Jeremy Fitzhardinge
2011-09-02 0:55 ` [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking Jeremy Fitzhardinge
2011-09-02 14:47 ` Peter Zijlstra
2011-09-02 19:29 ` Jeremy Fitzhardinge
2011-09-02 20:47 ` Peter Zijlstra
2011-09-02 21:50 ` Jeremy Fitzhardinge
2011-09-02 22:37 ` Peter Zijlstra
2011-09-02 23:14 ` Andi Kleen
2011-09-05 11:52 ` Stefano Stabellini
2011-09-05 12:05 ` Avi Kivity
2011-09-06 15:14 ` Don Zickus
2011-09-06 18:07 ` Jeremy Fitzhardinge
2011-09-06 18:27 ` Don Zickus
2011-09-06 18:50 ` Jeremy Fitzhardinge
2011-09-07 4:13 ` Avi Kivity
2011-09-07 13:44 ` Don Zickus
2011-09-07 15:11 ` Avi Kivity
2011-09-07 15:56 ` Don Zickus
2011-09-07 16:25 ` Avi Kivity
2011-09-07 16:52 ` Don Zickus
2011-09-07 17:09 ` Avi Kivity
2011-09-07 17:17 ` Jeremy Fitzhardinge
2011-09-07 17:41 ` Avi Kivity
2011-09-07 19:09 ` Jeremy Fitzhardinge
2011-09-08 7:51 ` Avi Kivity [this message]
2011-09-08 17:29 ` Jeremy Fitzhardinge
2011-09-11 9:59 ` Avi Kivity
2011-09-07 17:21 ` Don Zickus
2011-09-07 17:41 ` Avi Kivity
2011-09-13 18:40 ` Don Zickus
2011-09-13 19:03 ` Andi Kleen
2011-09-13 19:21 ` Don Zickus
2011-09-13 19:58 ` Andi Kleen
2011-09-13 20:53 ` Don Zickus
2011-09-13 21:04 ` Andi Kleen
2011-09-14 7:00 ` Avi Kivity
2011-09-14 12:49 ` Don Zickus
2011-09-14 14:49 ` Andi Kleen
2011-09-14 15:01 ` Avi Kivity
2011-09-14 17:28 ` Andi Kleen
2011-09-14 19:26 ` Avi Kivity
2011-09-14 19:34 ` Andi Kleen
2011-09-14 19:56 ` Avi Kivity
2011-09-13 19:27 ` Don Zickus
2011-09-02 0:55 ` [PATCH 09/13] x86/pvticketlocks: we only need to kick if there's waiters Jeremy Fitzhardinge
2011-09-02 0:55 ` [PATCH 10/13] xen/pvticket: allow interrupts to be enabled while blocking Jeremy Fitzhardinge
2011-09-02 14:48 ` Peter Zijlstra
2011-09-02 19:30 ` Jeremy Fitzhardinge
2011-09-02 0:55 ` [PATCH 11/13] x86/ticketlock: only do kick after doing unlock Jeremy Fitzhardinge
2011-09-02 14:49 ` Peter Zijlstra
2011-09-02 19:34 ` Jeremy Fitzhardinge
2011-09-02 0:55 ` [PATCH 12/13] x86/pvticketlock: make sure unlock_kick pvop call is inlined Jeremy Fitzhardinge
2011-09-02 0:55 ` [PATCH 13/13] x86/pvticketlock: use __ticket_t for pvop args Jeremy Fitzhardinge
2011-09-02 11:22 ` [PATCH 00/13] [PATCH RFC] Paravirtualized ticketlocks Stefano Stabellini
2011-09-06 19:33 ` Jeremy Fitzhardinge
2011-09-02 15:38 ` Linus Torvalds
2011-09-02 20:07 ` Jeremy Fitzhardinge
2011-09-02 20:27 ` Linus Torvalds
2011-09-02 21:42 ` Jeremy Fitzhardinge
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