On Mon, Dec 14, 2009 at 10:08:38PM +0200, Gleb Natapov wrote: > On Mon, Dec 14, 2009 at 02:02:03PM -0600, Anthony Liguori wrote: > > Gleb Natapov wrote: > > >>I thought KVM emulates the syscall instruction? I swear I've seen > > >>patches for that. > > >> > > >It is. Starting from 2.6.32. > > > > Okay, so this is a performance vs. migration compatibility issue then? > > > > BTW, couldn't we just not advertise syscall in cpuid? That should > > fix it too without sacrificing migration compatibility. We get a > > slight slowdown on AMD hosts but that's probably minor compared to > > the cost of using emulated syscall on Intel hosts. > > > As far as I understand not advertising syscall for 64bit CPU is not a > valid option.
Yes. 64 bit kernel 32 bit userpace crashes with -cpu qemu64,-syscall. > -- > Gleb.
