On Tue, Nov 03, 2009 at 07:15:10AM +0200, Avi Kivity wrote: > On 11/02/2009 06:18 PM, Gleb Natapov wrote: > >>>+#define KVM_PV_SHM_VERSION 1 > >>versions = bad, feature bits = good > >> > >I have both! Do you want me to drop version? > > Yes. Once a kernel is released you can't realistically change the version. > Why not? If version doesn't match apf will not be used. > >>Some documentation for this? > >> > >>Also, the name should reflect the pv pagefault use. For other uses > >>we can register other areas. > >> > >I wanted it to be generic, but I am fine with making it apf specific. > >It will allow to make it smaller too. > > Maybe we can squeeze it into the page-fault error code? > apf has to pass two things into a guest kernel: - event type (page not present/wake up) - unique token Error code has 32 bits and at least 1 of them should indicate that this is apf another one should indicate event type so this leaves us 30 bits for a token. 12 bits of a token is used to store vcpu id this leaves 18 bits for unique per vcpu id. Yes this may be enough. I don't think it is realistic to have more then 200000 outstanding apfs per vcpu. Alternately we can use CR2 to pass a token. > >>would solve this. I prefer using put_user() though than a permanent > >>get_user_pages(). > >> > >I want to prevent it from been swapped out. > > Since you don't prevent the page fault handler or code from being > swapped out, you don't get anything out of it. > Performance. Currently it is accessed on each page fault and to access it gup+kmap should be done each and every time. -- 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
