Re: [libvirt] [PATCH qom-cpu 02/11] target-i386: Disable kvm_mmu_op by default on pc-1.4

On Fri, Jan 04, 2013 at 08:01:03PM -0200, Eduardo Habkost wrote: > The kvm_mmu_op feature was removed from the kernel since v3.3 (released > in March 2012), it was marked for removal since January 2011 and it's > slower than shadow or hardware assisted paging (see kernel commit > fb92045843). It doesn't make sense to keep it enabled by default. > Actually it was effectively removed Oct 1 2009 by a68a6a7282373. After 3 and a half years of not having it I think we can safely drop it without trying to preserve it in older machine types.

> Also, keeping it enabled by default would cause unnecessary hassle when > libvirt start using the "enforce" option. > > Signed-off-by: Eduardo Habkost <ehabkost(a)redhat.com&gt; > --- > Cc: kvm(a)vger.kernel.org > Cc: Michael S. Tsirkin <mst(a)redhat.com&gt; > Cc: Gleb Natapov <gleb(a)redhat.com&gt; > Cc: Marcelo Tosatti <mtosatti(a)redhat.com&gt; > Cc: libvir-list(a)redhat.com > Cc: Jiri Denemark <jdenemar(a)redhat.com&gt; > > I was planning to reverse the logic of the compat init functions and > make pc_init_pci_1_3() enable kvm_mmu_op and then call pc_init_pci_1_4() > instead. But that would require changing pc_init_pci_no_kvmclock() and > pc_init_isa() as well. So to keep the changes simple, I am keeping the > pattern used when pc_init_pci_1_3() was introduced, making > pc_init_pci_1_4() disable kvm_mmu_op and then call pc_init_pci_1_3(). > > Changes v2: > - Coding style fix > - Removed redundant comments above machine init functions > --- > hw/pc_piix.c | 9 ++++++++- > target-i386/cpu.c | 9 +++++++++ > target-i386/cpu.h | 1 + > 3 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/hw/pc_piix.c b/hw/pc_piix.c > index 99747a7..a32af6a 100644 > --- a/hw/pc_piix.c > +++ b/hw/pc_piix.c > @@ -217,6 +217,7 @@ static void pc_init1(MemoryRegion *system_memory, > } > } > > +/* machine init function for pc-0.14 - pc-1.2 */ > static void pc_init_pci(QEMUMachineInitArgs *args) > { > ram_addr_t ram_size = args->ram_size; > @@ -238,6 +239,12 @@ static void pc_init_pci_1_3(QEMUMachineInitArgs *args) > pc_init_pci(args); > } > > +static void pc_init_pci_1_4(QEMUMachineInitArgs *args) > +{ > + disable_kvm_mmu_op(); > + pc_init_pci_1_3(args); > +} > + > static void pc_init_pci_no_kvmclock(QEMUMachineInitArgs *args) > { > ram_addr_t ram_size = args->ram_size; > @@ -285,7 +292,7 @@ static QEMUMachine pc_machine_v1_4 = { > .name = "pc-1.4", > .alias = "pc", > .desc = "Standard PC", > - .init = pc_init_pci_1_3, > + .init = pc_init_pci_1_4, > .max_cpus = 255, > .is_default = 1, > }; > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > index e6435da..c83a566 100644 > --- a/target-i386/cpu.c > +++ b/target-i386/cpu.c > @@ -158,6 +158,15 @@ void enable_kvm_pv_eoi(void) > #endif > } > > +void disable_kvm_mmu_op(void) > +{ > +#ifdef CONFIG_KVM No need for ifdef here too.