[Xen-devel] Re: regression on Xen: 23573 breaks PV on HVM guests

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 25.07.11 at 13:34, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
wrote:
> On Mon, 25 Jul 2011, Jan Beulich wrote:
>> >>> On 25.07.11 at 12:54, Stefano Stabellini 
>> >>> <stefano.stabellini@xxxxxxxxxxxxx> 
> wrote:
>> > Hi all,
>> > I would just let you know that I found a regression in the hypervisor:
>> > CS 23573 causes PV on HVM guests to hang during boot.
>> 
>> Any details (e.g. state of the guest, messages from the hypervisor)
>> that might help finding out what the problem is? I'm not aware that I
>> intentionally changed anything behavior-wise in the pv-on-hvm specific
>> code
> 
> I think that 23573 introduced a problem similar to the one solved by
> 23550, that is hvm_domain_use_pirq returns a subtly wrong answer.

Hmm, indeed, seems like I failed to remove the check of the assigned
event channel when I merged my patch with the changes from 23550.

Could you give the below a try?

Jan

--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1991,6 +1991,5 @@ int unmap_domain_pirq_emuirq(struct doma
 bool_t hvm_domain_use_pirq(const struct domain *d, const struct pirq *pirq)
 {
     return is_hvm_domain(d) && pirq &&
-           pirq->arch.hvm.emuirq != IRQ_UNBOUND &&
-           pirq->evtchn != 0;
+           pirq->arch.hvm.emuirq != IRQ_UNBOUND;
 }

> In any case it is really easy to reproduce: download a recent upstream
> kernel tree (3.0.0 is fine), enable CONFIG_XEN, make sure you have:
> 
> CONFIG_XEN=y
> CONFIG_PCI_XEN=y
> CONFIG_XEN_BLKDEV_FRONTEND=y
> CONFIG_XEN_NETDEV_FRONTEND=y
> CONFIG_XEN_XENBUS_FRONTEND=y
> CONFIG_XEN_PLATFORM_PCI=y
> 
> that's all. Try to boot the kernel in an HVM guest and it will hang.




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