linux-kernel - Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)

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Message-Id: <200712031416.51710.amit.shah@qumranet.com>
Date:	Mon, 3 Dec 2007 14:16:51 +0530
From:	Amit Shah <amit.shah@...ranet.com>
To:	kvm-devel@...ts.sourceforge.net
Cc:	Anthony Liguori <aliguori@...ibm.com>,
	linux-kernel@...r.kernel.org, Avi Kivity <avi@...ranet.com>
Subject: Re: [kvm-devel] [PATCH] Refactor hypercall infrastructure (v2)

* 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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