Re: [PATCH: kvm 3/6] Fix hotadd of CPUs for KVM.

Marcelo Tosatti
2009-09-24T15:52:44Z

On Wed, Sep 23, 2009 at 05:29:02PM -1000, Zachary Amsden wrote:
> Both VMX and SVM require per-cpu memory allocation, which is done at module
> init time, for only online cpus. When bringing a new CPU online, we must
> also allocate this structure. The method chosen to implement this is to
> make the CPU online notifier available via a call to the arch code. This
> allows memory allocation to be done smoothly, without any need to allocate
> extra structures.
>
> Note: CPU up notifiers may call KVM callback before calling cpufreq callbacks.
> This would causes the CPU frequency not to be detected (and it is not always
> clear on non-constant TSC platforms what the bringup TSC rate will be, so the
> guess of using tsc_khz could be wrong). So, we clear the rate to zero in such
> a case and add logic to query it upon entry.
>
> Signed-off-by: Zachary Amsden <zamsden@redhat.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/svm.c | 15 +++++++++++++--
> arch/x86/kvm/vmx.c | 17 +++++++++++++++++
> arch/x86/kvm/x86.c | 14 +++++++++++++-
> include/linux/kvm_host.h | 6 ++++++
> virt/kvm/kvm_main.c | 3 ++-
> 6 files changed, 53 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 299cc1b..b7dd14b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -459,6 +459,7 @@ struct descriptor_table {
> struct kvm_x86_ops {
> int (*cpu_has_kvm_support)(void); /* __init */
> int (*disabled_by_bios)(void); /* __init */
> + int (*cpu_hotadd)(int cpu);
> int (*hardware_enable)(void *dummy);
> void (*hardware_disable)(void *dummy);
> void (*check_processor_compatibility)(void *rtn);
> @@ -791,6 +792,7 @@ asmlinkage void kvm_handle_fault_on_reboot(void);
> _ASM_PTR " 666b, 667b \n\t" \
> ".popsection"
>
> +#define KVM_ARCH_WANT_HOTPLUG_NOTIFIER
> #define KVM_ARCH_WANT_MMU_NOTIFIER
> int kvm_unmap_hva(struct kvm *kvm, unsigned long hva);
> int kvm_age_hva(struct kvm *kvm, unsigned long hva);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 9a4daca..8f99d0c 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -330,13 +330,13 @@ static int svm_hardware_enable(void *garbage)
> return -EBUSY;
>
> if (!has_svm()) {
> - printk(KERN_ERR "svm_cpu_init: err EOPNOTSUPP on %d\n", me);
> + printk(KERN_ERR "svm_hardware_enable: err EOPNOTSUPP on %d\n", me);
> return -EINVAL;
> }
> svm_data = per_cpu(svm_data, me);
>
> if (!svm_data) {
> - printk(KERN_ERR "svm_cpu_init: svm_data is NULL on %d\n",
> + printk(KERN_ERR "svm_hardware_enable: svm_data is NULL on %d\n",
> me);
> return -EINVAL;
> }
> @@ -394,6 +394,16 @@ err_1:
>
> }
>
> +static __cpuinit int svm_cpu_hotadd(int cpu)
> +{
> + struct svm_cpu_data *svm_data = per_cpu(svm_data, cpu);
> +
> + if (svm_data)
> + return 0;
> +
> + return svm_cpu_init(cpu);
> +}
> +
> static void set_msr_interception(u32 *msrpm, unsigned msr,
> int read, int write)
> {
> @@ -2858,6 +2868,7 @@ static struct kvm_x86_ops svm_x86_ops = {
> .hardware_setup = svm_hardware_setup,
> .hardware_unsetup = svm_hardware_unsetup,
> .check_processor_compatibility = svm_check_processor_compat,
> + .cpu_hotadd = svm_cpu_hotadd,
> .hardware_enable = svm_hardware_enable,
> .hardware_disable = svm_hardware_disable,
> .cpu_has_accelerated_tpr = svm_cpu_has_accelerated_tpr,
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 3fe0d42..b8a8428 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1408,6 +1408,22 @@ static __exit void hardware_unsetup(void)
> free_kvm_area();
> }
>
> +static __cpuinit int vmx_cpu_hotadd(int cpu)
> +{
> + struct vmcs *vmcs;
> +
> + if (per_cpu(vmxarea, cpu))
> + return 0;
> +
> + vmcs = alloc_vmcs_cpu(cpu);
> + if (!vmcs)
> + return -ENOMEM;
> +
> + per_cpu(vmxarea, cpu) = vmcs;
> +
> + return 0;
> +}

Have to free in __cpuexit?

Is it too wasteful to allocate statically with DEFINE_PER_CPU_PAGE_ALIGNED?