Re: [PATCH] pci: ensure valid link status bits for downstream ports

[Zhenyu Zhang]

On 2024/11/11 20:37, Sebastian Ott wrote:

> PCI hotplug for downstream endpoints on arm fails because Linux'
> PCIe hotplug driver doesn't like the QEMU provided LNKSTA:
>
>   pcieport 0000:08:01.0: pciehp: Slot(2): Card present
>   pcieport 0000:08:01.0: pciehp: Slot(2): Link Up
>   pcieport 0000:08:01.0: pciehp: Slot(2): Cannot train link: status 0x2000
>
> There's 2 cases where LNKSTA isn't setup properly:
> * the downstream device has no express capability
> * max link width of the bridge is 0
>
> Fix these by making the LNKSTA modifications independent of each other.
>
> Signed-off-by: Sebastian Ott <sebott@redhat.com>
> ---
>  hw/pci/pcie.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
> index 0b455c8654..f714f4fb7c 100644
> --- a/hw/pci/pcie.c
> +++ b/hw/pci/pcie.c
> @@ -1109,20 +1109,20 @@ void pcie_sync_bridge_lnk(PCIDevice *bridge_dev)
>          lnksta = target->config_read(target,
>                                       target->exp.exp_cap + PCI_EXP_LNKSTA,
>                                       sizeof(lnksta));
> -
> -        if ((lnksta & PCI_EXP_LNKSTA_NLW) > (lnkcap & PCI_EXP_LNKCAP_MLW)) {
> -            lnksta &= ~PCI_EXP_LNKSTA_NLW;
> -            lnksta |= lnkcap & PCI_EXP_LNKCAP_MLW;
> -        } else if (!(lnksta & PCI_EXP_LNKSTA_NLW)) {
> -            lnksta |= QEMU_PCI_EXP_LNKSTA_NLW(QEMU_PCI_EXP_LNK_X1);
> -        }
> -
> -        if ((lnksta & PCI_EXP_LNKSTA_CLS) > (lnkcap & PCI_EXP_LNKCAP_SLS)) {
> -            lnksta &= ~PCI_EXP_LNKSTA_CLS;
> -            lnksta |= lnkcap & PCI_EXP_LNKCAP_SLS;
> -        } else if (!(lnksta & PCI_EXP_LNKSTA_CLS)) {
> -            lnksta |= QEMU_PCI_EXP_LNKSTA_CLS(QEMU_PCI_EXP_LNK_2_5GT);
> -        }
> +    }
> +    if ((lnksta & PCI_EXP_LNKSTA_NLW) > (lnkcap & PCI_EXP_LNKCAP_MLW)) {
> +        lnksta &= ~PCI_EXP_LNKSTA_NLW;
> +        lnksta |= lnkcap & PCI_EXP_LNKCAP_MLW;
> +    }
> +    if (!(lnksta & PCI_EXP_LNKSTA_NLW)) {
> +        lnksta |= QEMU_PCI_EXP_LNKSTA_NLW(QEMU_PCI_EXP_LNK_X1);
> +    }
> +    if ((lnksta & PCI_EXP_LNKSTA_CLS) > (lnkcap & PCI_EXP_LNKCAP_SLS)) {
> +        lnksta &= ~PCI_EXP_LNKSTA_CLS;
> +        lnksta |= lnkcap & PCI_EXP_LNKCAP_SLS;
> +    }
> +    if (!(lnksta & PCI_EXP_LNKSTA_CLS)) {
> +        lnksta |= QEMU_PCI_EXP_LNKSTA_CLS(QEMU_PCI_EXP_LNK_2_5GT);
>      }
>  
>      pci_word_test_and_clear_mask(exp_cap + PCI_EXP_LNKSTA,
>

[PATCH] pci: ensure valid link status bits for downstream ports

Test on aarch64 host(v9.2.0-rc0-1-gbde0d70333)
PCI hotplug for downstream endpoints on arm succeed
The test results are as expected.


Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>