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b4a7a1ea1a
An issue reported on KBL NUC (No APIC-V), when runing GVT test
case, it is easily to cause SOS/UOS hung. This patch is to root
cause it and how to avoid it.
On some platforms with no APIC-V support, this modidication can
avoid SOS hung when no IRR but event pending bit set.
If no APIC-V, interrupt injection will use IRR in vLAPIC and
event pending bitmap; work logic as following (set ABC for notes):
1. in ISR or when UOS send an interrupt to SOS/VHM (like IO request),
step A: set IRR --> step B: set event pending bit;
2. in SOS event handing, step C: check/clear event pending bit -->
step D: probe/get IRR --> step E: clear/handle IRR.
3. after that, it will probe IRR again to check if other IRR left:
step F: probe IRR --> step G: set event pending bit --> step H:
enable IRQ window in VMX.
Before, from step C to D, if pending bit checked, but no IRR, it will
return -1, then the CPU will goto ZOMBIE status. It can cause
SOS hung. It can happen occasionally under following case :
4. between UOS step A and step B, SOS can goto step F, so it
gets IRR, and step G --> step H, then SOS enter non-root mode, for
IRQ window enabled, it will cause vmexit to continue step C/D/E.
5. then UOS does step B, to set pending bit, but no IRR now. When next
vmexit, SOS does step C and D, it can't get IRR, failure happens.
In summary, a failed case steps: A-->F-->G-->H-->C-->D-->E-->B-->C-->D
So we allow that when event pending bit checked, IRR could be cleared
already.It just wastes one probe time occasionally.
Tracked-On: #1363
Signed-off-by: Minggui Cao <minggui.cao@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>