On 14.09.2017 21:25, Greg Kurz wrote: > On a server-class ppc host, this capability depends on the KVM type, > ie, HV or PR. If both KVM are present in the kernel, we will always > get the HV specific value, even if we explicitely requested PR on > the command line. > > This can have an impact if we're using hugepages or a balloon device. > > Since we've already created the VM at the time any user calls > kvm_has_sync_mmu(), switching to kvm_vm_check_extension() is > enough to fix any potential issue. > > It is okay for the other archs that also implement KVM_CAP_SYNC_MMU, > ie, mips, s390, x86 and arm, because they don't depend on the VM being > created or not. > > Signed-off-by: Greg Kurz <gr...@kaod.org> > --- > accel/kvm/kvm-all.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index f85553a85194..323c567cfb68 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -2234,7 +2234,7 @@ int kvm_device_access(int fd, int group, uint64_t attr, > /* Return 1 on success, 0 on failure */ > int kvm_has_sync_mmu(void) > { > - return kvm_check_extension(kvm_state, KVM_CAP_SYNC_MMU); > + return kvm_vm_check_extension(kvm_state, KVM_CAP_SYNC_MMU); > }
Reviewed-by: Thomas Huth <th...@redhat.com> ... but while you're at it, maybe it would be better to use a bool variable for the state of this extension, too, and only check for the extension one time at the end of kvm_init() ? kvm_has_sync_mmu() is apparently used multiple times in other source files, so we might be able to save some cycles by doing the syscall only once? Thomas