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Re: [Xen-devel] [PATCH v4] Hvmloader: Modify ACPI to only supply _EJ0 methods for PCIslots that support hotplug by runtime patching

On 05/09/2014 12:12 PM, Ian Campbell wrote:
On Fri, 2014-05-09 at 12:00 -0400, Konrad Rzeszutek Wilk wrote:

So we could just then gat the _EJ0 functionality based on values that
are present (or not) in the SSDT ?

AIUI the very presence of _EJ0 is what marks the device as being
ejectable (e.g. in the Windows device manager).

It would be possible to make _EJ0 conditionally turn itself into a NOP
without resorting to an SSDT, but I don't think that solves the issue
they are trying to solve, which is that the user can even try to eject
an non-hotplug device. (grep for UAR1 in our dsdt.asl and
acpi_info->com1_present in hvmloader/acpi/build.c for an example of this
sort of conditional thing)

Yea that is a good point. Windows probably cannot survive the attempt to eject. The spec sort of implies the OSPM should check to see that it was ejected properly but nothing about how a failed eject would be handled.

"OSPM verifies the device no longer exists to determine if the eject succeeded."

And then BSODs...


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Ross Philipson

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