> On Apr 29, 2020, at 3:45 PM, Michael S. Tsirkin <m...@redhat.com> wrote: > > On Wed, Apr 29, 2020 at 09:14:26AM +0000, Ani Sinha wrote: >> >> >>> On Apr 29, 2020, at 2:26 PM, Michael S. Tsirkin <m...@redhat.com> wrote: >>> >>> Even if it seems to work for guests now, if we don't stick to emulating >>> capabilities that hardware interfaces provide we can never be sure it >>> will keep working. >> >> OS es use ACPI for PCI bridges: >> https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_qemu_qemu_blob_master_docs_pcie.txt&d=DwIFaQ&c=s883GpUCOChKOHiocYtGcg&r=IIUxIyRwG4RGy57y2nvMNYcDkqW-NHozZ2R38VYcg5U&m=9AnuR62iRsUnmV9ggkS_lqen67etHeCjATFLwCJWxQs&s=As__N9BXf0DTSZkD4cxaQsTeg0exh5GSPqkFSh7fxRk&e= >> >> They use “_EJ0” to detect jot unplug capability: >> https://urldefense.proofpoint.com/v2/url?u=https-3A__uefi.org_sites_default_files_resources_ACPI-5F3.pdf&d=DwIFaQ&c=s883GpUCOChKOHiocYtGcg&r=IIUxIyRwG4RGy57y2nvMNYcDkqW-NHozZ2R38VYcg5U&m=9AnuR62iRsUnmV9ggkS_lqen67etHeCjATFLwCJWxQs&s=SDgOhKGpnlzfbvAOFl2m9a-tdPZEUcCwKWsgkVDafyM&e= >> >> >> 6.3.3 _EJx (Eject) These control methods are optional and are supplied for >> devices that support a software-controlled VCRstyle ejection mechanism or >> that require an action be performed such as isolation of power/data lines >> before the device can be removed from the system. To support warm (system is >> in a sleep state) and hot (system is in S0) removal, an _EJx control method >> is listed for each sleep state from which the device supports removal, where >> x is the sleeping state supported. For example, _EJ0 indicates the device >> supports hot removal; _EJ1–EJ4 indicate the device supports warm removal. > > Yes. So if there's no _EJx then it's reasonable to assume you can't > isolate the slot, and so no hot-plug will happen either.
Where are you getting that? This isn’t true. “_SUN” is used to detect the slot unique number. Windows does allow hot plugging on the bridge on which EJ0 has been turned off. > >> >> Note that “these control methods are optional” line. If the OS adheres to >> the spec, it should not expect them to exist all the time. >> > > > > -- > MST >
