Re: [PATCH 10/11] XEN / PCI: Remove the dependence on arch x86 when PCI_MMCONFIG=y

[Hanjun Guo]

On 2015å05æ26æ 23:44, Boris Ostrovsky wrote:
> On 05/26/2015 10:54 AM, Tomasz Nowicki wrote:
> > On 26.05.2015 16:00, Boris Ostrovsky wrote:
> > > On 05/26/2015 09:54 AM, Boris Ostrovsky wrote:
> > > > On 05/26/2015 08:49 AM, Hanjun Guo wrote:
> > > > > In drivers/xen/pci.c, there are arch x86 dependent codes when
> > > > > CONFIG_PCI_MMCONFIG is enabled, since CONFIG_PCI_MMCONFIG
> > > > > depends on ACPI, so this will prevent XEN PCI running on other
> > > > > architectures using ACPI with PCI_MMCONFIG enabled (such as ARM64).
> > > > >
> > > > > Fortunatly, it can be sloved in a simple way. In drivers/xen/pci.c,
> > > > > the only x86 dependent code is if ((pci_probe & PCI_PROBE_MMCONF) ==
> > > > > 0),
> > > > > and it's defined in asm/pci_x86.h, the code means that
> > > > > if the PCI resource is not probed in PCI_PROBE_MMCONF way, just
> > > > > ingnore the xen mcfg init. Actually this is duplicate, because
> > > > > if PCI resource is not probed in PCI_PROBE_MMCONF way, the
> > > > > pci_mmconfig_list will be empty, and the if (list_empty())
> > > > > after it will do the same job.
> > > > >
> > > > > So just remove the arch related code and the head file, this
> > > > > will be no functional change for x86, and also makes xen/pci.c
> > > > > usable for other architectures.
> > > > >
> > > > > Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
> > > > > CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > > > > CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> > > > > ---
> > > > >   drivers/xen/pci.c | 6 ------
> > > > >   1 file changed, 6 deletions(-)
> > > > >
> > > > > diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
> > > > > index 6785ebb..9a8dbe3 100644
> > > > > --- a/drivers/xen/pci.c
> > > > > +++ b/drivers/xen/pci.c
> > > > > @@ -28,9 +28,6 @@
> > > > >   #include <asm/xen/hypervisor.h>
> > > > >   #include <asm/xen/hypercall.h>
> > > > >   #include "../pci/pci.h"
> > > > > -#ifdef CONFIG_PCI_MMCONFIG
> > > > > -#include <asm/pci_x86.h>
> > > > > -#endif
> > > > >
> > > > >   static bool __read_mostly pci_seg_supported = true;
> > > > >
> > > > > @@ -222,9 +219,6 @@ static int __init xen_mcfg_late(void)
> > > > >       if (!xen_initial_domain())
> > > > >           return 0;
> > > > >
> > > > > -    if ((pci_probe & PCI_PROBE_MMCONF) == 0)
> > > > > -        return 0;
> > > > > -
> > > > >       if (list_empty(&pci_mmcfg_list))
> > > > >           return 0;
> > > >
> > > > (+Stefano who is Xen ARM maintainer)
> > > >
> > > > This will not build on x86 since pci_mmcfg_list since, for example,
> > > > pci_mmcfg_list is declared in pci_x86.h.
> > >
> > >
> > > And now really with Stefano and with parsable first sentence, sorry:
> > >
> > >
> > > This will not build on x86 since pci_mmcfg_list, for example, is
> > > declared in pci_x86.h.
> >
> > With this patch set, not any more. Please see preceding patches.
>
>
> OK, I didn't notice this was part of a series.

Sorry, I didn't cc you all of those patches.

> Then if not having PCI_PROBE_MMCONF bit set is indeed equivalent to
> list_empty(&pci_mmcfg_list), is there any reason for this flag to
> (continue to) exist? (and also for pci_mmcfg_arch_init_failed.)

I think PCI_PROBE_MMCONF bit is needed for early init of pci mmconfig in
the x86 arch related code, but for xen_mcfg_late(), it's called after
acpi_init() which the mmconfig is ready for use if it's available (the
pci_mmcfg_list is empty or not), so not having PCI_PROBE_MMCONF bit set
is equivalent list_empty(&pci_mmcfg_list) is not suitable for all cases,
but I think it will be ok after mmconfig is initialized.

I think my change log is misleading and needs updating :)

Thanks
Hanjun
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