From: Dexuan Cui <decui@microsoft.com>
Sent: Tuesday, September 8, 2020 4:18 PM

Hyper-V doesn't trap and emulate the accesses to the MSI/MSI-X registers,
and we must use hv_compose_msi_msg() to ask Hyper-V to create the IOMMU
Interrupt Remapping Table Entries. This is not an issue for a lot of
PCI device drivers (e.g. NVMe driver, Mellanox NIC drivers), which
destroy and re-create the interrupts across hibernation, so
hv_compose_msi_msg() is called automatically. However, some other PCI
device drivers (e.g. the Nvidia driver) may not destroy and re-create
the interrupts across hibernation, so hv_pci_resume() has to call
hv_compose_msi_msg(), otherwise the PCI device drivers can no longer
receive MSI/MSI-X interrupts after hibernation.

Fixes: ac82fc832708 ("PCI: hv: Add hibernation support")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Jake Oshins <redacted>

---

Changes in v2:
    Fixed a typo in the comment in hv_irq_unmask. Thanks to Michael!
    Added Jake's Reviewed-by.

 drivers/pci/controller/pci-hyperv.c | 44 +++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

Hi Lorenzo, Bjorn,
Can you please take a look at this patch? 
I hope it still could have a chance to be in 5.9. :-)

Thanks,
-- Dexuan