Re: [Xen-devel] [PATCH 4.1] x86: fix emuirq regression from XSA-21 fix (was: Re: [PATCH] xen: reuse the same pirq allocated when driver load first time)

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.06.13 at 13:03, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
wrote:
> On Tue, 25 Jun 2013, Stefano Stabellini wrote:
>> On Tue, 25 Jun 2013, Jan Beulich wrote:
>> > >>> On 25.06.13 at 07:33, DuanZhenzhong <zhenzhong.duan@xxxxxxxxxx> wrote:
>> > > Stefano Stabellini wrote:
>> > >> On Mon, 24 Jun 2013, Zhenzhong Duan wrote:
>> > >>> Could you have a look if there is something wrong in xen side of 
>> > >>> clearing 
>> > >>> the mapping?
>> > >>
>> > >> What I am saying is that the error you are getting:
>> > >>
>> > >> pt_msix_disable: Unbind msix with pirq 67, gvec 0
>> > >> pt_msix_disable: Unmap msix with pirq 67
>> > >> pt_msix_disable: Error: Unmapping of MSI-X failed. [00:04.0]
>> > >>
>> > >> cannot be caused by domain_pirq_to_emuirq(d, pirq) returning
>> > >> IRQ_UNBOUND.
>> > >> So, why are you getting this error? What is failing?
>> > >> I am ready to believe the problem is in Xen but Without understanding
>> > >> why you are getting the error it's hard to find a solution.
>> > >>   
>> > > I found the reason, you are looking at xen-unstable, I was working with 
>> > > 4.1.30-OVM, it has patch of CVE-2012-4536 / XSA-21.
>> > > That patch set ret to -EINVAL initially. After remove that line, unmap 
>> > > succeed.
>> > 
>> > Removing that line certainly isn't right. The proper fix is the one
>> > below/attached.
>> > 
>> > Jan
>> > 
>> > ****************************************************
>> > x86: fix emuirq regression from XSA-21 fix
>> > 
>> > The XSA-21 patch broke the assumption of "ret" being zero prior to the
>> > IRQ_UNBOUND check.
>> > 
>> > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> > 
>> > --- a/xen/arch/x86/physdev.c
>> > +++ b/xen/arch/x86/physdev.c
>> > @@ -243,6 +243,8 @@ static int physdev_unmap_pirq(struct phy
>> >          spin_lock(&d->event_lock);
>> >          if ( domain_pirq_to_emuirq(d, unmap->pirq) != IRQ_UNBOUND )
>> >              ret = unmap_domain_pirq_emuirq(d, unmap->pirq);
>> > +        else
>> > +            ret = 0;
>> >          spin_unlock(&d->event_lock);
>> >          if ( unmap->domid == DOMID_SELF || ret )
>> >              goto free_domain;
>> 
>> 
>> This is unnecessary.
>> ret is 0 regardless because of the previous:
>> 
>> ret = xsm_unmap_domain_pirq(XSM_TARGET, d);
>>
> 
> Ops, I read now the patch for XSA-21.
> The change above is fine (and makes the code more readable anyway).

So is this some odd way of saying Reviewed-by?

Jan


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