* Avi Kivity <[EMAIL PROTECTED]> wrote: > Ingo Molnar wrote: > >Subject: [patch] kvm: fix GFP_KERNEL allocation in atomic section in > >kvm_dev_ioctl_create_vcpu() > >From: Ingo Molnar <[EMAIL PROTECTED]> > > > >fix an GFP_KERNEL allocation in atomic section: > >kvm_dev_ioctl_create_vcpu() called kvm_mmu_init(), which calls > >alloc_pages(), while holding the vcpu. > > > >The fix is to set up the MMU state in two phases: kvm_mmu_create() and > >kvm_mmu_setup(). > > > >(NOTE: free_vcpus does an kvm_mmu_destroy() call so there's no need > > for any extra teardown branch on allocation/init failure here.) > > > >Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]> > > > > Applied, thanks.
great! I've got a security related question as well: vcpu_load() sets up a physical CPU's VM registers/state, and vcpu_put() drops that. But vcpu_put() only does a put_cpu() call - it does not tear down any VM state that has been loaded into the CPU. Is it guaranteed that (hostile) user-space cannot use that VM state in any unauthorized way? The state is still loaded while arbitrary tasks execute on the CPU. The next vcpu_load() will then override it, but the state lingers around forever. The new x86 VM instructions: vmclear, vmlaunch, vmresume, vmptrld, vmread, vmwrite, vmxoff, vmxon are all privileged so i guess it should be mostly safe - i'm just wondering whether you thought about this attack angle. ultimately we want to integrate VM state management into the scheduler and the context-switch lowlevel arch code, but right now CPU state management is done by the KVM 'driver' and there's nothing that isolates other tasks from possible side-effects of a loaded VMX/SVN state. Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/