X86/KVM: Do not allow DISABLE_EXITS_MWAIT when LAPIC ARAT is not available

Browse source

If the processor does not have an "Always Running APIC Timer" (aka ARAT),
we should not give guests direct access to MWAIT. The LAPIC timer would
stop ticking in deep C-states, so any host deadlines would not wakeup the
host kernel.

The host kernel intel_idle driver handles this by switching to broadcast
mode when ARAT is not available and MWAIT is issued with a deep C-state
that would stop the LAPIC timer. When MWAIT is passed through, we can not
tell when MWAIT is issued.

So just disable this capability when LAPIC ARAT is not available. I am not
even sure if there are any CPUs with VMX support but no LAPIC ARAT or not.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Reported-by: Wanpeng Li <kernellwp@gmail.com>
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

...

This commit is contained in:

KarimAllah Ahmed 2018-04-11 11:16:03 +02:00 • committed by Paolo Bonzini

parent 4d5f26ee31

commit 8e9b29b618

1 changed files with 2 additions and 1 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

3

arch/x86/kvm/x86.c

View file