On 20.03.25 22:07, Bjorn Helgaas wrote:
On Wed, Feb 19, 2025 at 10:20:57AM +0100, Roger Pau Monne wrote:Setting pci_msi_ignore_mask inhibits the toggling of the mask bit for both MSI and MSI-X entries globally, regardless of the IRQ chip they are using. Only Xen sets the pci_msi_ignore_mask when routing physical interrupts over event channels, to prevent PCI code from attempting to toggle the maskbit, as it's Xen that controls the bit. However, the pci_msi_ignore_mask being global will affect devices that use MSI interrupts but are not routing those interrupts over event channels (not using the Xen pIRQ chip). One example is devices behind a VMD PCI bridge. In that scenario the VMD bridge configures MSI(-X) using the normal IRQ chip (the pIRQ one in the Xen case), and devices behind the bridge configure the MSI entries using indexes into the VMD bridge MSI table. The VMD bridge then demultiplexes such interrupts and delivers to the destination device(s). Having pci_msi_ignore_mask set in that scenario prevents (un)masking of MSI entries for devices behind the VMD bridge. Move the signaling of no entry masking into the MSI domain flags, as that allows setting it on a per-domain basis. Set it for the Xen MSI domain that uses the pIRQ chip, while leaving it unset for the rest of the cases. Remove pci_msi_ignore_mask at once, since it was only used by Xen code, and with Xen dropping usage the variable is unneeded. This fixes using devices behind a VMD bridge on Xen PV hardware domains. Albeit Devices behind a VMD bridge are not known to Xen, that doesn't mean Linux cannot use them. By inhibiting the usage of VMD_FEAT_CAN_BYPASS_MSI_REMAP and the removal of the pci_msi_ignore_mask bodge devices behind a VMD bridge do work fine when use from a Linux Xen hardware domain. That's the whole point of the series. Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Acked-by: Juergen Gross <jgross@xxxxxxxx>Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> I assume you'll merge this series via the Xen tree. Let me know if otherwise.
I've pushed the series to the linux-next branch of the Xen tree. Juergen
Attachment:
OpenPGP_0xB0DE9DD628BF132F.asc
Description: OpenPGP public key
Attachment:
OpenPGP_signature.asc
Description: OpenPGP digital signature
