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Re: [Xen-devel] [Patch] x86: enforce strict memory order for x2apic
| To: | "Tian, Kevin" <kevin.tian@xxxxxxxxx>, 'Jan Beulich' <jbeulich@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [Patch] x86: enforce strict memory order for x2apic |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Thu, 25 Sep 2008 09:36:19 +0100 |
| Cc: | |
| Delivery-date: | Thu, 25 Sep 2008 01:37:02 -0700 |
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| Thread-topic: | [Xen-devel] [Patch] x86: enforce strict memory order for x2apic |
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On 25/9/08 09:29, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote: >> On the other hand you're penalizing LAPIC systems with this, too. I'm >> not certain that's better than fixing the (incorrect) >> assumptions just in >> the x2APIC case. > > I agree. I'll revise the patch to add a 'mb()' in x2APIC instead, > though that may bring a bit overhead to cases when fencing > is not required, like event check IPI. To be precise, mb() at top of send_IPI_mask_x2apic(), and wmb() may as well go from on_selected_cpus() as we can assume send_IPI_mask() is a barrier. I'll do the patch for this myself. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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