The extended LVT entries can be used to configure interrupt delivery
for various events that are internal to a processor and can use this
feature.
All current processors that support the feature have four of such entries.
The entries are all masked upon the processor reset, but it's possible
that firmware may use some of them.
BIOS and Kernel Developer's Guides for some processor models do not assign
any particular names to the extended LVTs, while other BKDGs provide names
and suggested usage for them.
However, there is no fixed mapping between the LVTs and the processor
events in any processor model that supports the feature. Any entry can be
assigned to any event. The assignment is done by programming an offset
of an entry into configuration bits corresponding to an event.
This change does not expose the flexibility that the feature offers.
The change adds just a single method to configure a hardcoded extended LVT
entry to deliver APIC_CMC_INT. The method is designed to be used with
Machine Check Error Thresholding mechanism on supported processor models.
For references please see BKDGs for families 10h - 16h and specifically
descriptions of APIC30, APIC400, APIC[530:500] registers.
For a description of the Error Thresholding mechanism see, for example,
BKDG for family 10h, section 2.12.1.6.
http://developer.amd.com/resources/developer-guides-manuals/
Thanks to jhb and kib for their suggestions.
Reviewed by: kib
Discussed with: jhb
MFC after: 5 weeks
Relnotes: maybe
Differential Revision: https://reviews.freebsd.org/D9612
hw.x2apic_enable tunable allows disabling it from the loader prompt.
To closely repeat effects of the uncached memory ops when accessing
registers in the xAPIC mode, the x2APIC writes to MSRs are preceeded
by mfence, except for the EOI notifications. This is probably too
strict, only ICR writes to send IPI require serialization to ensure
that other CPUs see the previous actions when IPI is delivered. This
may be changed later.
In vmm justreturn IPI handler, call doreti_iret instead of doing iretd
inline, to handle corner conditions.
Note that the patch only switches LAPICs into x2APIC mode. It does not
enables FreeBSD to support > 255 CPUs, which requires parsing x2APIC
MADT entries and doing interrupts remapping, but is the required step
on the way.
Reviewed by: neel
Tested by: pho (real hardware), neel (on bhyve)
Discussed with: jhb, grehan
Sponsored by: The FreeBSD Foundation
MFC after: 2 months
