Re: [External] Re: [PATCH] hw/pci/pcie.c: Fix invalid PCI_EXP_LNKCAP setting

[Wenliang Wang]

As PCI_EXP_LNKCAP is never masked when loading, this patch does affect 
cross version migration. It seems we need machine type compat to deal 
with that. What do you suggest, Michael?

On 5/20/22 12:49 AM, Michael S. Tsirkin wrote:
> On Thu, May 19, 2022 at 10:45:59PM +0800, Wenliang Wang wrote:
> > pcie_cap_fill_slot_lnk() wrongly set PCI_EXP_LNKCAP when slot speed
> > and width is not set, causing strange downstream port link cap
> > (Speed unknown, Width x0) and pcie devices native hotplug error on Linux:
> >
> > [    3.545654] pcieport 0000:02:00.0: pciehp: link training error: status 0x2000
> > [    3.547143] pcieport 0000:02:00.0: pciehp: Failed to check link status
> >
> > We do not touch PCI_EXP_LNKCAP when speed=0 or width=0, as pcie_cap_v1_fill()
> > already do the default setting for us.
> >
> > Signed-off-by: Wenliang Wang <wangwenliang.1995@bytedance.com>
>
>
> do we need machine type compat dance with this?
> can you check whether this affects cross version
> migration please?
>
> > ---
> >   hw/pci/pcie.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
> > index 68a62da..c82e7fc 100644
> > --- a/hw/pci/pcie.c
> > +++ b/hw/pci/pcie.c
> > @@ -92,6 +92,11 @@ static void pcie_cap_fill_slot_lnk(PCIDevice *dev)
> >           return;
> >       }
> >   
> > +    /* Use default LNKCAP setting */
> > +    if (s->speed == 0 || s->width == 0) {
> > +        return;
> > +    }
> > +
> >       /* Clear and fill LNKCAP from what was configured above */
> >       pci_long_test_and_clear_mask(exp_cap + PCI_EXP_LNKCAP,
> >                                    PCI_EXP_LNKCAP_MLW | PCI_EXP_LNKCAP_SLS);
> > --
> > 2.7.4