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)

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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).

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