| Message ID | 20200722161722.51416-1-mlevitsk@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | RFC: pcie: parital fix for missing unplug events | expand |
On Wed, Jul 22, 2020 at 07:17:21PM +0300, Maxim Levitsky wrote: > As described in bugzilla #1854264 it is possible to plug > a pcie device and then unplug it before the guest notices > (has time to process the attention button press) > > To partially fix this issue, detect and refuse the hotunplug event. > > There are other ways to fix this, which is why I am sending this as RFC: > > 1. Queue/remember the unplug event and fire it (press the attention button again), > when the guest clears its pending status. > According to the spec this should cancel the hotplug event in the guest > if done within 5 seconds (and I think that guest actually should wait 5 seconds > after attention button is pressed before plugging in the device too to be strictly > up to the spec) > > 2. Detect that device isn't yet powered on by the guest (for example > checking the bus master bit) or check that attention button is still > pressed and in this case just unplug the device immediately. I think 2 or failing that 1 would be preferable. > Best regards, > Maxim Levitsky > > Maxim Levitsky (1): > pci/pcie: refuse another hotplug/unplug event if attention button is > pending > > hw/pci/pcie.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > -- > 2.26.2 >
As described in bugzilla #1854264 it is possible to plug a pcie device and then unplug it before the guest notices (has time to process the attention button press) To partially fix this issue, detect and refuse the hotunplug event. There are other ways to fix this, which is why I am sending this as RFC: 1. Queue/remember the unplug event and fire it (press the attention button again), when the guest clears its pending status. According to the spec this should cancel the hotplug event in the guest if done within 5 seconds (and I think that guest actually should wait 5 seconds after attention button is pressed before plugging in the device too to be strictly up to the spec) 2. Detect that device isn't yet powered on by the guest (for example checking the bus master bit) or check that attention button is still pressed and in this case just unplug the device immediately. Best regards, Maxim Levitsky Maxim Levitsky (1): pci/pcie: refuse another hotplug/unplug event if attention button is pending hw/pci/pcie.c | 11 +++++++++++ 1 file changed, 11 insertions(+)