From: Amit Shah <amit.shah@qumranet.com>
To: kvm-devel@lists.sourceforge.net
Subject: Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)
Date: Mon, 3 Dec 2007 14:16:51 +0530
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Cc: Anthony Liguori <aliguori@us.ibm.com>, linux-kernel@vger.kernel.org,
       Avi Kivity <avi@qumranet.com>
References: <11898788932902-git-send-email-aliguori@us.ibm.com> <200712021917.28706.amit.shah@qumranet.com> <475339A6.9020207@us.ibm.com>
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* Anthony Liguori wrote:
> Amit Shah wrote:
> > * Anthony Liguori wrote:
> > ?
> >
> >> This patch refactors the current hypercall infrastructure to better
> >> support live migration and SMP. ?It eliminates the hypercall page by
> >> trapping the UD exception that would occur if you used the wrong
> >> hypercall instruction for the underlying architecture and replacing it
> >> with the right one lazily. 
> >
> > This doesn't work right for SVM. It keeps looping indefinitely; on a
> > kvm_stat run, I get about 230,000 light vm exits per second, with the
> > hypercall never returning to the guest.
> >
> > ...
> > ?
>
> What are you using to issue the hypercall?

+       r = kvm_hypercall1(KVM_PV_PCI_DEVICE, page_gfn);

Setup is done by:

+       if (!kvm_para_available()) {
+               printk(KERN_ERR "KVM paravirt support not available\n");
+               r = -ENODEV;
+               goto out_dereg;
+       }

I also couldn't get the has_feature to work properly.

See:

http://lkml.org/lkml/2007/11/7/129

I had to change the hypercall address to 0f 01 d9 for it to get working.

>
> Regards,
>
> Anthony Liguori


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