On Mon, Mar 11, 2013 at 02:31:46PM +0100, Paolo Bonzini wrote: > Il 11/03/2013 12:51, Gleb Natapov ha scritto: > >> > > >> > Agreed, but we still have the problem of how to signal from userspace. > >> > For that do you have any other suggestion than mp_state? And if we keep > >> > mp_state to signal from userspace, giving INIT_RECEIVED the > >> > "wait-for-SIPI" semantics would be wrong. > >> > > > I don't see how can we use mp_state for signaling from userspace either. > > Currently soft reset always reset vcpus, so it is OK for userspace to > > generate reset vcpu state and put it into kernel, mp_state is just one > > of the updated states, but when INIT will be just another signal that > > may or may not reset cpu or have other side effects like #vmexit this > > will not longer work. We will have to have another interface for > > injecting INIT from userspace and userspace soft-reset will use it > > instead of doing reset by itself. > > Setting the mp_state to INIT_RECEIVED is that interface, and it already > works, for APs at least. This patch extends it to work for the BSP as well. > It does not for AP either. If AP has vmx on mp_sate should not be set to INIT_RECEIVED. mp_sate is a state as you can see from its name and we already had a discussion on the generic device API about importance of separating sending commands from setting state. There is a difference between setting mp_sate during migration and signaling INIT#. > In the corresponding userspace patch, I don't need to touch the CPU > state at all. I can just signal the kernel. If I touch the CPU, I'll > break the nested case, no matter how it is implemented. So far, the > userspace did not have to worry about nested, and that's something that > should be kept that way. We are discussing two different things here. I'll try to separate them. 1. BSP is broken WRT #INIT 2. nested is broken WRT #INIT You are fixing 1 with your patches, for that I proposed much easier solution (at last from kernel point of view): if BSP reset it in userspace and make it runnable. Nested virt is still broken, but this is not what you are fixing. For 2 much more involved fix is needed. Jan fixes it and it will require signaling INIT# from userspace by other means than mp_sate because signaling INIT# does not automatically means that mp_sate changes to INIT_RECEIVED. > > If we move away from the INIT_RECEIVED and SIPI_RECEIVED states for > in-kernel APIC -> VCPU communication, then the KVM_SET_MP_STATE ioctl > will have to convert them to the right bits in the requests field or in > the APIC state. But I'm starting to see less benefit from moving away > from mp_state. > We are not moving away from mp_state, we are moving away from using mp_state for signaling because with nested virt INIT does not always change mp_state, not only that it can change mp_state long after signal is received after vmx off is done. -- Gleb. -- 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
