Re: [Qemu-devel] [PATCH] pcie: fix device hotplug failure at the meantime of VM boot

[Zhangbo (Oscar)]

>-----Original Message-----
>From: Philippe Mathieu-Daudé [mailto:address@hidden]
>Sent: Tuesday, July 23, 2019 5:18 PM
>To: Zhangbo (Oscar) <address@hidden>; address@hidden
>Cc: fangying <address@hidden>; dengkai (A) <address@hidden>;
>limingwang (A) <address@hidden>; address@hidden
>Subject: Re: [Qemu-devel] [PATCH] pcie: fix device hotplug failure at the
>meantime of VM boot
>
>Hi Oscar,
>
>On 7/23/19 9:47 AM, Zhangbo (Oscar) wrote:
>> If the PCI_EXP_LNKSTA_DLLLA capability is set by default, linux kernel will 
>> send
>> PDC event to detect whether there is a device in pcie slot. If a device is 
>> pluged
>> in the pcie-root-port at the same time, hot-plug device will send ABP + PDC
>> events to the kernel. The VM kernel will wrongly unplug the device if two PDC
>> events get too close. Thus we'd better set the PCI_EXP_LNKSTA_DLLLA
>> capability only in hotplug callback.
>>
>> By the way, we should clean up the PCI_EXP_LNKSTA_DLLLA capability during
>> unplug to avoid VM restart or migration failure which will enter the same
>> abnormal scenario as above.
>>
>> Signed-off-by: address@hidden
>> Signed-off-by: address@hidden
>
>QEMU contribution guideline says:
>
>  Please use your real name to sign a patch (not an alias or acronym).
>
Thanks for reminding, I've sent a patch V2 just now, plz check there.

>See:
>https://wiki.qemu.org/Contribute/SubmitAPatch#Patch_emails_must_include_a
>_Signed-off-by:_line
>
>We can infer limingwang@ real name is Liming Wang, oscar.zhangbo@ is
>Oscar Zhangbo, but for fangying1@ it is too hard.
>Can you provide his real name?
>
>Thanks,
>
>Phil.
>
>> Signed-off-by: address@hidden
>> ---
>>  hw/pci/pcie.c | 9 +++++----
>>  1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
>> index a6beb56..174f392 100644
>> --- a/hw/pci/pcie.c
>> +++ b/hw/pci/pcie.c
>> @@ -75,10 +75,6 @@ pcie_cap_v1_fill(PCIDevice *dev, uint8_t port, uint8_t
>type, uint8_t version)
>>
>QEMU_PCI_EXP_LNKSTA_NLW(QEMU_PCI_EXP_LNK_X1) |
>>
>QEMU_PCI_EXP_LNKSTA_CLS(QEMU_PCI_EXP_LNK_2_5GT));
>>
>> -    if (dev->cap_present & QEMU_PCIE_LNKSTA_DLLLA) {
>> -        pci_word_test_and_set_mask(exp_cap + PCI_EXP_LNKSTA,
>> -                                   PCI_EXP_LNKSTA_DLLLA);
>> -    }
>>
>>      /* We changed link status bits over time, and changing them across
>>       * migrations is generally fine as hardware changes them too.
>> @@ -484,6 +480,11 @@ void
>pcie_cap_slot_unplug_request_cb(HotplugHandler *hotplug_dev,
>>          return;
>>      }
>>
>> +    if (pci_dev->cap_present & QEMU_PCIE_LNKSTA_DLLLA) {
>> +        pci_word_test_and_clear_mask(exp_cap + PCI_EXP_LNKSTA,
>> +                                     PCI_EXP_LNKSTA_DLLLA);
>> +    }
>> +
>>      pcie_cap_slot_push_attention_button(PCI_DEVICE(hotplug_dev));
>>  }
>>
>>