Re: [Xen-devel] [PATCH] x86/mmcfg/drhd: Move acpi_mmcfg_init() before calling acpi_parse_dmar()

[Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>]

在 2018/8/16 18:37, Jan Beulich 写道:
> > > > On 16.08.18 at 11:13, <zhenzhong.duan@xxxxxxxxxx> wrote:
> > On 2018/8/16 15:10, Jan Beulich wrote:
> > > Have you investigated the alternative of deferring acpi_dmar_init()
> > > to a later point, or at least the part of it that needs to do PCI
> > > config space accesses? I'm not currently convinced the device scope
> > > parsing needs to happen that early: Neither iommu_supports_eim()
> > > nor iommu_enable_x2apic_IR() look to depend on that information
> > > at the first glance, and I think these are the routines that require
> > > (part of) the DMAR parsing to happen early.
> > I moved acpi_mmcfg_init() ahead of acpi_boot_init() because below code
> > sequence depending on pci_mmcfg_virt being correctly setup.
> > acpi_dmar_init
> >     ->acpi_parse_dmar
> >       ->acpi_parse_one_drhd
> >         ->acpi_parse_dev_scope
> >           ->pci_conf_read8
> >             ->pci_mmcfg_read
> >               ->pci_dev_base
> >                 ->get_virt
> Have you read my previous response in full? I'm specifically asking
> whether the device scope parsing (i.e. acpi_parse_dev_scope())
> really needs to happen as early as it does now. Without that, the
> dependency on MMCFG accesses working would go away.
I'll move acpi_dmar_init() to later point to have a test as 
acpi_parse_one_drhd, acpi_parse_one_rmrr and acpi_parse_one_atsr all 
called acpi_parse_dev_scope.
> > > > --- a/xen/arch/x86/setup.c
> > > > +++ b/xen/arch/x86/setup.c
> > > > @@ -1493,6 +1493,10 @@ void __init noreturn __start_xen(unsigned long mbi_p)
> > > >    
> > > >        generic_apic_probe();
> > > >    
> > > > +    pt_pci_init();
> > > > +
> > > > +    acpi_mmcfg_init();
> > > > +
> > > >        acpi_boot_init();
> > > With the dependency being _in_ acpi_boot_init(), the invocation of
> > > acpi_mmcfg_init() should now be moved there.
> > Yes, I feel better to move pt_pci_init() and acpi_mmcfg_init() in
> > acpi_boot_init() before acpi_mmcfg_init().
> I didn't say move both, did I?
>
> That said, now having looked at what it actually does, I think you want
> to rename it if the suggested alternative route can't be used, as in
> particular the pt_ prefix is quite misleading then. Once that has
> happened, moving the invocation perhaps even _into_ acpi_mcfg_init()
Understood.
Personly I like this way more as pt_pci_init() and acpi_mmcfg_init() 
only initialized some global variable and harmless to move ahead. Also 
acpi_mcfg_init from its name is suitable to move in acpi_boot_init()
Thanks
Zhenzhong

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