On (Fri) Jul 17 2009 [11:48:32], Rakesh Avichal Ughreja wrote: > Hello All, > > I am trying to understand the what is the connection between KVM and QEMU. > > The way I understand it so far from the information on the net, KVM is > an emulator for x86 based machine and it uses the virtualization > support provided by the x86 based CPUs. QEMU is a generic emulator and > has support for many CPUs apart from x86. I am not sure if QEMU makes > use of virtualization support from CPU. I think this would be noted in quite a few places but here it is again: qemu is the emulator. If kvm support is present, qemu uses that to speed up the guest. qemu can emulate several architecture / processor types but kvm can only run x86 on x86, ppc on ppc, etc., ie, the guest has to be of the same type as the host. > If I am correct in the above statement then I think the from the x86 > point of view KVM would have an advantage in terms of speed and > performance while running it on the x86 CPUs which has virtualization > support. Is there any other advantage of using KVM over QEMU ? > > Any pointer/documentation would surely be helpful. http://www.linux-kvm.org/page/Documents > Also while going through the KVM-88 source code I came across > pre-processor directives KVM_CAP_IRQCHIP, can anyone tell me what is > the use of this flag ? That means the kernel has support for emulating the irqchip. The support also exists in qemu but if it's also present in the kernel, use that so that guest interrupt handling is faster. > I am trying to understand how interrupt controller is implemented in > KVM, how the devices can generate interrupts and how the OS ISR will > be called. see the files in virt/kvm/ and arch/x86/kvm/ > > Thank you. Amit -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
