On Fri, Jan 4, 2013 at 2:52 PM, Eduardo Habkost <ehabk...@redhat.com> 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.
>
> Also, keeping it enabled by default would cause unnecessary hassle when
> libvirt start using the "enforce" option.
>
> Signed-off-by: Eduardo Habkost <ehabk...@redhat.com>
> ---
> Cc: kvm@vger.kernel.org
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Cc: Gleb Natapov <g...@redhat.com>
> Cc: Marcelo Tosatti <mtosa...@redhat.com>
> Cc: libvir-l...@redhat.com
> Cc: Jiri Denemark <jdene...@redhat.com>
>
> 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(). 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().
>
> ---
> hw/pc_piix.c | 11 ++++++++++-
> target-i386/cpu.c | 8 ++++++++
> target-i386/cpu.h | 1 +
> 3 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> index 99747a7..a6bf645 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;
> @@ -232,12 +233,20 @@ static void pc_init_pci(QEMUMachineInitArgs *args)
> initrd_filename, cpu_model, 1, 1);
> }
>
> +/* machine init function for pc-1.3 */
The comment does give much information compared to the function name.
> static void pc_init_pci_1_3(QEMUMachineInitArgs *args)
> {
> enable_kvm_pv_eoi();
> pc_init_pci(args);
> }
>
> +/* machine init function for pc-1.4 */
Ditto.
> +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 +294,7 @@ 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 808001a..ec877c7 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -157,6 +157,14 @@ void enable_kvm_pv_eoi(void)
> #endif
> }
>
> +void disable_kvm_mmu_op(void)
> +{
> +#ifdef CONFIG_KVM
> + if (kvm_enabled())
Braces.
> + kvm_default_features &= ~(1UL << KVM_FEATURE_MMU_OP);
> +#endif
> +}
> +
> void host_cpuid(uint32_t function, uint32_t count,
> uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx)
> {
> diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> index 1283537..27c8d0c 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -1219,5 +1219,6 @@ void do_smm_enter(CPUX86State *env1);
> void cpu_report_tpr_access(CPUX86State *env, TPRAccess access);
>
> void enable_kvm_pv_eoi(void);
> +void disable_kvm_mmu_op(void);
>
> #endif /* CPU_I386_H */
> --
> 1.7.11.7
>
>
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