[PATCH] KVM: add KVM_SYNC_SHADOW_WITH_USER ioctl (v2)

[PATCH] KVM: add KVM_SYNC_SHADOW_WITH_USER ioctl (v2)

[Marcelo Tosatti]

Export nukeing of shadow MMU pages through an ioctl, required for
consistency on balloon inflate.

Changes:
- Move to x86-specific kvm_arch_vm_ioctl() 
- Grab mmap_sem

Index: kvm.quilt/arch/x86/kvm/x86.c
===================================================================
--- kvm.quilt.orig/arch/x86/kvm/x86.c
+++ kvm.quilt/arch/x86/kvm/x86.c
@@ -680,6 +680,7 @@ int kvm_dev_ioctl_check_extension(long e
 	case KVM_CAP_USER_MEMORY:
 	case KVM_CAP_SET_TSS_ADDR:
 	case KVM_CAP_EXT_CPUID:
+	case KVM_CAP_SYNC_SHADOW_WITH_USER:
 		r = 1;
 		break;
 	case KVM_CAP_VAPIC:
@@ -1505,6 +1506,13 @@ long kvm_arch_vm_ioctl(struct file *filp
 		r = 0;
 		break;
 	}
+	case KVM_SYNC_SHADOW_WITH_USER: {
+		r = 0;
+		down_read(&current->mm->mmap_sem);
+		kvm_mmu_zap_all(kvm);
+		up_read(&current->mm->mmap_sem);
+		break;
+	}
 	default:
 		;
 	}
Index: kvm.quilt/include/linux/kvm.h
===================================================================
--- kvm.quilt.orig/include/linux/kvm.h
+++ kvm.quilt/include/linux/kvm.h
@@ -249,6 +249,7 @@ struct kvm_vapic_addr {
 #define KVM_CAP_SET_TSS_ADDR 4
 #define KVM_CAP_EXT_CPUID 5
 #define KVM_CAP_VAPIC 6
+#define KVM_CAP_SYNC_SHADOW_WITH_USER 7
 
 /*
  * ioctls for VM fds
@@ -267,6 +268,7 @@ struct kvm_vapic_addr {
 #define KVM_GET_DIRTY_LOG         _IOW(KVMIO, 0x42, struct kvm_dirty_log)
 #define KVM_SET_MEMORY_ALIAS      _IOW(KVMIO, 0x43, struct kvm_memory_alias)
 #define KVM_GET_SUPPORTED_CPUID   _IOWR(KVMIO, 0x48, struct kvm_cpuid2)
+#define KVM_SYNC_SHADOW_WITH_USER _IO(KVMIO, 0x49)
 /* Device model IOC */
 #define KVM_CREATE_IRQCHIP	  _IO(KVMIO,  0x60)
 #define KVM_IRQ_LINE		  _IOW(KVMIO, 0x61, struct kvm_irq_level)

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Re: [PATCH] KVM: add KVM_SYNC_SHADOW_WITH_USER ioctl (v2)

[Avi Kivity]

Marcelo Tosatti wrote:
> Export nukeing of shadow MMU pages through an ioctl, required for
> consistency on balloon inflate.
>
>   

With mmu notifiers (posted two minutes after this) shadow is implicitly 
synced with userspace.  Since it seems to be progressing rapidly, I 
won't apply this patch in the hope that mmu notifiers can be ready for 
2.6.25.

-- 
Any sufficiently difficult bug is indistinguishable from a feature.


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Re: [PATCH] KVM: add KVM_SYNC_SHADOW_WITH_USER ioctl (v2)

[Anthony Liguori]

Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> Export nukeing of shadow MMU pages through an ioctl, required for
>> consistency on balloon inflate.
>>
>>   
>
> With mmu notifiers (posted two minutes after this) shadow is 
> implicitly synced with userspace.  Since it seems to be progressing 
> rapidly, I won't apply this patch in the hope that mmu notifiers can 
> be ready for 2.6.25.

Does that mean that we'll only support ballooning on host kernels > 
2.6.25 are you going to do judo with debug registers to implement it for 
older kernels?

Regards,

Anthony Liguori


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Re: [PATCH] KVM: add KVM_SYNC_SHADOW_WITH_USER ioctl (v2)

[Avi Kivity]

Anthony Liguori wrote:
>>>   
>>
>> With mmu notifiers (posted two minutes after this) shadow is 
>> implicitly synced with userspace.  Since it seems to be progressing 
>> rapidly, I won't apply this patch in the hope that mmu notifiers can 
>> be ready for 2.6.25.
>
> Does that mean that we'll only support ballooning on host kernels > 
> 2.6.25 are you going to do judo with debug registers to implement it 
> for older kernels?

Good question.  We may choose not to support it (distros may backport it 
if they wish), or do some evil hackery, or apply 
KVM_SYNC_SHADOW_WITH_USER _only_ to the external module.

-- 
Any sufficiently difficult bug is indistinguishable from a feature.


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