[PATCH v6 2/2] KVM-INTEL: add a notifier and a bitmap to support VMCLEAR in kdump

[Marcelo Tosatti]

On Wed, Nov 21, 2012 at 11:27:19PM +0800, Zhang Yanfei wrote:
> The notifier will be registered in vmclear_notifier_list when loading
> kvm-intel module. And the bitmap indicates whether we should do
> VMCLEAR operation in kdump. The bits in the bitmap are set/unset
> according to different conditions.
> 
> Signed-off-by: Zhang Yanfei <zhangyanfei at cn.fujitsu.com>
> ---
>  arch/x86/kvm/vmx.c |   77 +++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 76 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 4ff0ab9..eea55b3 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -41,6 +41,7 @@
>  #include <asm/i387.h>
>  #include <asm/xcr.h>
>  #include <asm/perf_event.h>
> +#include <asm/kexec.h>
>  
>  #include "trace.h"
>  
> @@ -963,6 +964,49 @@ static void vmcs_load(struct vmcs *vmcs)
>  		       vmcs, phys_addr);
>  }
>  
> +#ifdef CONFIG_KEXEC
> +/*
> + * This bitmap is used to indicate whether the vmclear
> + * operation is enabled on all cpus. All disabled by
> + * default.
> + */
> +static cpumask_t crash_vmclear_enabled_bitmap = CPU_MASK_NONE;
> +
> +static inline void crash_enable_local_vmclear(int cpu)
> +{
> +	cpumask_set_cpu(cpu, &crash_vmclear_enabled_bitmap);
> +}
> +
> +static inline void crash_disable_local_vmclear(int cpu)
> +{
> +	cpumask_clear_cpu(cpu, &crash_vmclear_enabled_bitmap);
> +}
> +
> +static inline int crash_local_vmclear_enabled(int cpu)
> +{
> +	return cpumask_test_cpu(cpu, &crash_vmclear_enabled_bitmap);
> +}
> +
> +static void vmclear_local_loaded_vmcss(void);
> +static int crash_vmclear_local_loaded_vmcss(struct notifier_block *this,
> +					    unsigned long val, void *ptr)
> +{
> +	int cpu = raw_smp_processor_id();
> +
> +	if (crash_local_vmclear_enabled(cpu))
> +		vmclear_local_loaded_vmcss();
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block crash_vmclear_notifier = {
> +	.notifier_call = crash_vmclear_local_loaded_vmcss,
> +};
> +#else
> +static inline void crash_enable_local_vmclear(int cpu) { }
> +static inline void crash_disable_local_vmclear(int cpu) { }
> +#endif /* CONFIG_KEXEC */
> +
>  static void __loaded_vmcs_clear(void *arg)
>  {
>  	struct loaded_vmcs *loaded_vmcs = arg;
> @@ -972,8 +1016,10 @@ static void __loaded_vmcs_clear(void *arg)
>  		return; /* vcpu migration can race with cpu offline */
>  	if (per_cpu(current_vmcs, cpu) == loaded_vmcs->vmcs)
>  		per_cpu(current_vmcs, cpu) = NULL;
> +	crash_disable_local_vmclear(cpu);
>  	list_del(&loaded_vmcs->loaded_vmcss_on_cpu_link);
>  	loaded_vmcs_init(loaded_vmcs);
> +	crash_enable_local_vmclear(cpu);
>  }
>  
>  static void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs)
> @@ -1491,8 +1537,10 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  
>  		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
>  		local_irq_disable();
> +		crash_disable_local_vmclear(cpu);
>  		list_add(&vmx->loaded_vmcs->loaded_vmcss_on_cpu_link,
>  			 &per_cpu(loaded_vmcss_on_cpu, cpu));
> +		crash_enable_local_vmclear(cpu);
>  		local_irq_enable();
>  
>  		/*
> @@ -2302,6 +2350,18 @@ static int hardware_enable(void *garbage)
>  		return -EBUSY;
>  
>  	INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu));
> +
> +	/*
> +	 * Now we can enable the vmclear operation in kdump
> +	 * since the loaded_vmcss_on_cpu list on this cpu
> +	 * has been initialized.
> +	 *
> +	 * Though the cpu is not in VMX operation now, there
> +	 * is no problem to enable the vmclear operation
> +	 * for the loaded_vmcss_on_cpu list is empty!
> +	 */
> +	crash_enable_local_vmclear(cpu);
> +
>  	rdmsrl(MSR_IA32_FEATURE_CONTROL, old);
>  
>  	test_bits = FEATURE_CONTROL_LOCKED;
> @@ -2335,7 +2395,6 @@ static void vmclear_local_loaded_vmcss(void)
>  		__loaded_vmcs_clear(v);
>  }
>  
> -
>  /* Just like cpu_vmxoff(), but with the __kvm_handle_fault_on_reboot()
>   * tricks.
>   */
> @@ -2348,6 +2407,12 @@ static void hardware_disable(void *garbage)
>  {
>  	if (vmm_exclusive) {
>  		vmclear_local_loaded_vmcss();
> +		/*
> +		 * vmclear operation in kdump should be disabled here
> +		 * because the cpu is going to exit VMX operation
> +		 * and the loaded_vmcss_on_cpu list may not be empty!
> +		 */
> +		crash_disable_local_vmclear(raw_smp_processor_id());
>  		kvm_cpu_vmxoff();

How come its not empty? vmclear_local_loaded_vmcss cleared it, didnt it?