Re: [Xen-devel] [PATCH v5 7/7] VT-d: Fix vt-d Device-TLB flush timeout issue.

["Xu, Quan" <quan.xu@xxxxxxxxx>]

> On  February 18, 2016 5:21pm,  <JBeulich@xxxxxxxx> wrote:
> >>> On 18.02.16 at 09:47, <quan.xu@xxxxxxxxx> wrote:
> >>  On February 18, 2016 4:36pm, <JBeulich@xxxxxxxx> wrote:
> >> >>> On 18.02.16 at 08:36, <quan.xu@xxxxxxxxx> wrote:
> >> >>  On February 17, 2016 10:41pm, <JBeulich@xxxxxxxx> wrote:
> >> >> >>> On 05.02.16 at 11:18, <quan.xu@xxxxxxxxx> wrote:
> >> >> > --- a/xen/drivers/passthrough/vtd/qinval.c
> >> >> > +++ b/xen/drivers/passthrough/vtd/qinval.c
> >> >> > +            if ( pci_hide_device(bus, devfn) )
> >> >>
> >> >> But now I'm _really_ puzzled: You acquire the exact lock that
> >> >> pci_hide_device() acquires. Hence, unless I've overlooked an
> >> >> earlier change,
> >> > I
> >> >> can't see this as other than an unconditional dead lock. Did you
> >> >> test this
> >> > code
> >> >> path at all?
> >> >
> >> > Sorry, I didn't test this code path.
> >> > I did test the follows:
> >> >    1) Create domain with ATS device.
> >> >    2) Attach / Detach ATS device.
> >> >
> >> > I think I could add a variation of pci_hide_device(), without
> >> > "spin_lock(&pcidevs_lock) / spin_unlock(&pcidevs_lock)"
> >> > Or "__init".
> >>
> >> Which we already have - _pci_hide_device(). The function would just
> >> need to be made non-static, but would otherwise fit your purposes
> >> since you also don't need the alloc_pdev() the other function does.
> >
> > But the _pci_hide_device() starts with '_', I think it is not a good
> > idea to make it non-static.
> > I'd better introduce a new function to wrap the '_pci_hide_device()'.
> > It is difficult to name the new function.
> 
> Why add a wrapper - just rename the function (I indeed appreciate you not
> wanting to globalize a function whose name starts with an underscore), e.g. to
> pci_hide_device_locked() or pci_hide_existing_device().
>

Okay, I will rename the _pci_hide_device() to pci_hide_existing_device() in v6.
Quan


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