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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>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.