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

[Michael S. Tsirkin]

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