On Thu, 2023-11-02 at 15:41 -0500, Bjorn Helgaas wrote: > [+cc Kai-Heng] > > On Thu, Nov 02, 2023 at 01:07:03PM -0700, Nirmal Patel wrote: > > On Wed, 2023-11-01 at 17:20 -0500, Bjorn Helgaas wrote: > > > On Tue, Oct 31, 2023 at 12:59:34PM -0700, Nirmal Patel wrote: > > > > On Tue, 2023-10-31 at 10:31 -0500, Bjorn Helgaas wrote: > > > > > On Mon, Oct 30, 2023 at 04:16:54PM -0400, Nirmal Patel wrote: > > > > > > VMD Hotplug should be enabled or disabled based on VMD > > > > > > rootports' Hotplug configuration in BIOS. is_hotplug_bridge > > > > > > is set on each VMD rootport based on Hotplug capable bit in > > > > > > SltCap in probe.c. Check is_hotplug_bridge and enable or > > > > > > disable native_pcie_hotplug based on that value. > > > > > > > > > > > > Currently VMD driver copies ACPI settings or platform > > > > > > configurations for Hotplug, AER, DPC, PM, etc and enables > > > > > > or > > > > > > disables these features on VMD bridge which is not correct > > > > > > in case of Hotplug. > > > > > > > > > > This needs some background about why it's correct to copy the > > > > > ACPI settings in the case of AER, DPC, PM, etc, but incorrect > > > > > for hotplug. > > > > > > > > > > > Also during the Guest boot up, ACPI settings along with VMD > > > > > > UEFI driver are not present in Guest BIOS which results in > > > > > > assigning default values to Hotplug, AER, DPC, etc. As a > > > > > > result Hotplug is disabled on VMD in the Guest OS. > > > > > > > > > > > > This patch will make sure that Hotplug is enabled properly > > > > > > in Host as well as in VM. > > > > > > > > > > Did we come to some consensus about how or whether _OSC for > > > > > the host bridge above the VMD device should apply to devices > > > > > in the separate domain below the VMD? > > > > > > > > We are not able to come to any consensus. Someone suggested to > > > > copy either all _OSC flags or none. But logic behind that > > > > assumption is that the VMD is a bridge device which is not > > > > completely true. VMD is an endpoint device and it owns its > > > > domain. > > > > > > Do you want to facilitate a discussion in the PCI firmware SIG > > > about this? It seems like we may want a little text in the spec > > > about how to handle this situation so platforms and OSes have the > > > same expectations. > > > > The patch 04b12ef163d1 broke intel VMD's hotplug capabilities and > > author did not test in VM environment impact. > > We can resolve the issue easily by > > > > #1 Revert the patch which means restoring VMD's original > > functionality > > and author provide better fix. > > > > or > > > > #2 Allow the current change to re-enable VMD hotplug inside VMD > > driver. > > > > There is a significant impact for our customers hotplug use cases > > which > > forces us to apply the fix in out-of-box drivers for different OSs. > > I agree 100% that there's a serious problem here and we need to fix > it, there's no argument there. > > I guess you're saying it's obvious that an _OSC above VMD does not > apply to devices below VMD, and therefore, no PCI Firmware SIG > discussion or spec clarification is needed? Yes. By design VMD is an endpoint device to OS and its domain is privately owned by VMD only. I believe we should revert back to original design and not impose _OSC settings on VMD domain which is also a maintainable solution. > > I'm more interested in a long-term maintainable solution than a quick > fix. A maintainable solution requires an explanation for (a) why > _OSC > above VMD doesn't apply below VMD, and (b) consistency across > everything negotiated by _OSC, not just hotplug. The only reason I suggested to alter Hotplug because VMD has it's own independent Hotplug platform setting different from _OSC which is not the case for AER, DPC. So we can honor VMD's Hotplug BIOS settings as well as _OSC settings for other flags while maintaining functionalities across Host and Guest OSs. > > Bjorn
