On 9/12/19 2:31 PM, Igor Druzhinin wrote: > If MCFG area is not reserved in E820, Xen by default will defer its usage > until Dom0 registers it explicitly after ACPI parser recognizes it as > a reserved resource in DSDT. Having it reserved in E820 is not > mandatory according to "PCI Firmware Specification, rev 3.2" (par. 4.1.2) > and firmware is free to keep a hole in E820 in that place. Xen doesn't know > what exactly is inside this hole since it lacks full ACPI view of the > platform therefore it's potentially harmful to access MCFG region > without additional checks as some machines are known to provide > inconsistent information on the size of the region. > > Now xen_mcfg_late() runs after acpi_init() which is too late as some basic > PCI enumeration starts exactly there as well. Trying to register a device > prior to MCFG reservation causes multiple problems with PCIe extended > capability initializations in Xen (e.g. SR-IOV VF BAR sizing). There are > no convenient hooks for us to subscribe to so register MCFG areas earlier > upon the first invocation of xen_add_device(). It should be safe to do once > since all the boot time buses must have their MCFG areas in MCFG table > already and we don't support PCI bus hot-plug. > > Signed-off-by: Igor Druzhinin <igor.druzhi...@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrov...@oracle.com> and applied to for-linus-5.4
