Messages in this thread | | | Date | Mon, 29 Sep 2008 09:55:57 +0300 | From | Gleb Natapov <> | Subject | Re: Use CPUID to communicate with the hypervisor. |
| |
On Fri, Sep 26, 2008 at 04:46:55PM -0700, Alok Kataria wrote: > From: Alok N Kataria <akataria@vmware.com> > > This patch proposes to use a cpuid interface to detect if we are running on an > hypervisor. > The discovery of a hypervisor is determined by bit 31 of CPUID#1_ECX, which is > defined to be "hypervisor present bit". For a VM, the bit is 1, otherwise it is > set to 0. This bit is not officially documented by either Intel/AMD yet, but > they plan to do so some time soon, in the meanwhile they have promised to keep > it reserved for virtualization. > > Also, Intel & AMD have reserved the cpuid levels 0x40000000 - 0x400000FF for > software use. Hypervisors can use these levels to provide an interface to pass > information from the hypervisor to the guest. This is similar to how we extract > information about a physical cpu by using cpuid. > XEN/KVM are already using the info leaf to get the hypervisor signature. > Can this interface be used to pass variable sized data from a hypervisor to a gust? ACPI or DMI tables for instance.
-- Gleb.
| |