From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Sent: Monday, August 17, 2020 8:14 AM > > From: Wei Hu <weh@xxxxxxxxxxxxx> > > [ Upstream commit d6af2ed29c7c1c311b96dac989dcb991e90ee195 ] > > Kdump could fail sometime on Hyper-V guest because the retry in > hv_pci_enter_d0() releases child device structures in hv_pci_bus_exit(). > > Although there is a second asynchronous device relations message sending > from the host, if this message arrives to the guest after > hv_send_resource_allocated() is called, the retry would fail. > > Fix the problem by moving retry to hv_pci_probe() and start the retry > from hv_pci_query_relations() call. This will cause a device relations > message to arrive to the guest synchronously; the guest would then be > able to rebuild the child device structures before calling > hv_send_resource_allocated(). > > Link: > https://lore.kernel.org/linux-hyperv/20200727071731.18516-1-weh@xxxxxxxxxxxxx/ > Fixes: c81992e7f4aa ("PCI: hv: Retry PCI bus D0 entry on invalid device state") > Signed-off-by: Wei Hu <weh@xxxxxxxxxxxxx> > [lorenzo.pieralisi@xxxxxxx: fixed a comment and commit log] > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > drivers/pci/controller/pci-hyperv.c | 71 +++++++++++++++-------------- > 1 file changed, 37 insertions(+), 34 deletions(-) > Greg -- Don't backport this patch to 5.8 and earlier. It doesn't break anything, but it doesn't fully accomplish what was intended either. As such it will probably need a revision in 5.9. Wei Hu is unavailable for a few days for personal reasons, so I'm jumping in here on his behalf. Michael
