Subject: [PATCH v9 3/4] arm: dirty log write protect mgmt. Moved x86, armv7 to generic, set armv8 ia64 mips powerpc s390 arch specific

From: [email-masked] (Christoffer Dall)
Date: Mon, 11 Aug 2014 21:13:07 +0200

On Thu, Jul 24, 2014 at 05:56:07PM -0700, Mario Smarduch wrote:
> This patch adds support for keeping track of VM dirty pages. As dirty page log
> is retrieved, the pages that have been written are write protected again for
> next write and log read.
> 
> The dirty log read function is generic for armv7 and x86, and arch specific
> for arm64, ia64, mips, powerpc, s390.

So I would also split up this patch.  One that only modifies the
existing functionality, but does not introduce any new functionality for
ARM.  Put this first patch in the beginning of the patch series with the
other prepatory patch, so that you get something like this:

[PATCH 1/X] KVM: Add architecture-specific TLB flush implementations
[PATCH 2/X] KVM: Add generic implementation of kvm_vm_ioctl_get_dirty_log
[PATCH 3/X] arm: KVM: Add ARMv7 API to flush TLBs
[PATCH 4/X] arm: KVM: Add initial dirty page locking infrastructure
...

That will make it easier to get the patches accepted and for us to
review...

> 
> Signed-off-by: Mario Smarduch <[email-masked]>
> ---
>  arch/arm/kvm/arm.c                  |    8 +++-
>  arch/arm/kvm/mmu.c                  |   22 +++++++++
>  arch/arm64/include/asm/kvm_host.h   |    2 +
>  arch/arm64/kvm/Kconfig              |    1 +
>  arch/ia64/include/asm/kvm_host.h    |    1 +
>  arch/ia64/kvm/Kconfig               |    1 +
>  arch/ia64/kvm/kvm-ia64.c            |    2 +-
>  arch/mips/include/asm/kvm_host.h    |    2 +-
>  arch/mips/kvm/Kconfig               |    1 +
>  arch/mips/kvm/kvm_mips.c            |    2 +-
>  arch/powerpc/include/asm/kvm_host.h |    2 +
>  arch/powerpc/kvm/Kconfig            |    1 +
>  arch/powerpc/kvm/book3s.c           |    2 +-
>  arch/powerpc/kvm/booke.c            |    2 +-
>  arch/s390/include/asm/kvm_host.h    |    2 +
>  arch/s390/kvm/Kconfig               |    1 +
>  arch/s390/kvm/kvm-s390.c            |    2 +-
>  arch/x86/kvm/x86.c                  |   86 ---------------------------------
>  include/linux/kvm_host.h            |    3 ++
>  virt/kvm/Kconfig                    |    3 ++
>  virt/kvm/kvm_main.c                 |   90 +++++++++++++++++++++++++++++++++++
>  21 files changed, 143 insertions(+), 93 deletions(-)
> 
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index e11c2dd..f7739a0 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -783,10 +783,16 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
>  	}
>  }
>  
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +#ifdef CONFIG_ARM64
> +/*
> + * For now features not supported on ARM64, the #ifdef is added to make that
> + * clear but not needed since ARM64 Kconfig selects function in generic code.
> + */

I don't think this comment is needed, but if you really want it, it
should be something like:

/*
 * ARM64 does not support dirty logging and therefore selects
 * CONFIG_HAVE_KVM_ARCH_DIRTY_LOG.  Provide a -EINVAL stub.
 */

> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
>  {
>  	return -EINVAL;
>  }
> +#endif
>  
>  static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
>  					struct kvm_arm_device_addr *dev_addr)
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 7bfc792..ca84331 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -889,6 +889,28 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot)
>  	kvm_flush_remote_tlbs(kvm);
>  	spin_unlock(&kvm->mmu_lock);
>  }
> +
> +/**
> + * kvm_mmu_write_protected_pt_masked() - write protect dirty pages set in mask
> + * @kvm:	The KVM pointer
> + * @slot:	The memory slot associated with mask
> + * @gfn_offset:	The gfn offset in memory slot
> + * @mask:	The mask of dirty pages at offset 'gfn_offset' in this memory
> + *		slot to be write protected
> + *
> + * Walks bits set in mask write protects the associated pte's. Caller must
> + * acquire kvm_mmu_lock.
> + */
> +void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
> +		struct kvm_memory_slot *slot,
> +		gfn_t gfn_offset, unsigned long mask)
> +{
> +	phys_addr_t base_gfn = slot->base_gfn + gfn_offset;
> +	phys_addr_t start = (base_gfn +  __ffs(mask)) << PAGE_SHIFT;
> +	phys_addr_t end = (base_gfn + __fls(mask) + 1) << PAGE_SHIFT;

__fls(x) + 1 is the same as fls(x)
> +
> +	stage2_wp_range(kvm, start, end);
> +}
>  #endif
>  
>  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 92242ce..b4a280b 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -200,4 +200,6 @@ static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
>  		     hyp_stack_ptr, vector_ptr);
>  }
>  
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log);
> +
>  #endif /* __ARM64_KVM_HOST_H__ */
> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> index 8ba85e9..9e21a8a 100644
> --- a/arch/arm64/kvm/Kconfig
> +++ b/arch/arm64/kvm/Kconfig
> @@ -22,6 +22,7 @@ config KVM
>  	select PREEMPT_NOTIFIERS
>  	select ANON_INODES
>  	select HAVE_KVM_CPU_RELAX_INTERCEPT
> +	select HAVE_KVM_ARCH_DIRTY_LOG
>  	select KVM_MMIO
>  	select KVM_ARM_HOST
>  	select KVM_ARM_VGIC
> diff --git a/arch/ia64/include/asm/kvm_host.h b/arch/ia64/include/asm/kvm_host.h
> index db95f57..d79f520 100644
> --- a/arch/ia64/include/asm/kvm_host.h
> +++ b/arch/ia64/include/asm/kvm_host.h
> @@ -594,6 +594,7 @@ void kvm_sal_emul(struct kvm_vcpu *vcpu);
>  #define __KVM_HAVE_ARCH_VM_ALLOC 1
>  struct kvm *kvm_arch_alloc_vm(void);
>  void kvm_arch_free_vm(struct kvm *kvm);
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log);
>  
>  #endif /* __ASSEMBLY__*/
>  
> diff --git a/arch/ia64/kvm/Kconfig b/arch/ia64/kvm/Kconfig
> index 990b864..32dd6c8 100644
> --- a/arch/ia64/kvm/Kconfig
> +++ b/arch/ia64/kvm/Kconfig
> @@ -24,6 +24,7 @@ config KVM
>  	depends on BROKEN
>  	select PREEMPT_NOTIFIERS
>  	select ANON_INODES
> +	select HAVE_KVM_ARCH_DIRTY_LOG
>  	select HAVE_KVM_IRQCHIP
>  	select HAVE_KVM_IRQ_ROUTING
>  	select KVM_APIC_ARCHITECTURE
> diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
> index 6a4309b..3166df5 100644
> --- a/arch/ia64/kvm/kvm-ia64.c
> +++ b/arch/ia64/kvm/kvm-ia64.c
> @@ -1812,7 +1812,7 @@ static void kvm_ia64_sync_dirty_log(struct kvm *kvm,
>  	spin_unlock(&kvm->arch.dirty_log_lock);
>  }
>  
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm,
>  		struct kvm_dirty_log *log)
>  {
>  	int r;
> diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
> index 060aaa6..f7e2262 100644
> --- a/arch/mips/include/asm/kvm_host.h
> +++ b/arch/mips/include/asm/kvm_host.h
> @@ -649,6 +649,6 @@ extern int kvm_mips_trans_mtc0(uint32_t inst, uint32_t *opc,
>  extern void mips32_SyncICache(unsigned long addr, unsigned long size);
>  extern int kvm_mips_dump_stats(struct kvm_vcpu *vcpu);
>  extern unsigned long kvm_mips_get_ramsize(struct kvm *kvm);
> -
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log);
>  
>  #endif /* __MIPS_KVM_HOST_H__ */
> diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
> index 30e334e..b57f49e 100644
> --- a/arch/mips/kvm/Kconfig
> +++ b/arch/mips/kvm/Kconfig
> @@ -20,6 +20,7 @@ config KVM
>  	select PREEMPT_NOTIFIERS
>  	select ANON_INODES
>  	select KVM_MMIO
> +	select HAVE_KVM_ARCH_DIRTY_LOG
>  	---help---
>  	  Support for hosting Guest kernels.
>  	  Currently supported on MIPS32 processors.
> diff --git a/arch/mips/kvm/kvm_mips.c b/arch/mips/kvm/kvm_mips.c
> index da5186f..f9a1e62 100644
> --- a/arch/mips/kvm/kvm_mips.c
> +++ b/arch/mips/kvm/kvm_mips.c
> @@ -790,7 +790,7 @@ out:
>  /*
>   * Get (and clear) the dirty memory log for a memory slot.
>   */
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
>  {
>  	struct kvm_memory_slot *memslot;
>  	unsigned long ga, ga_end;
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 1eaea2d..fb31595 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -676,4 +676,6 @@ struct kvm_vcpu_arch {
>  #define __KVM_HAVE_ARCH_WQP
>  #define __KVM_HAVE_CREATE_DEVICE
>  
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log);
> +
>  #endif /* __POWERPC_KVM_HOST_H__ */
> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> index 141b202..c1fa061 100644
> --- a/arch/powerpc/kvm/Kconfig
> +++ b/arch/powerpc/kvm/Kconfig
> @@ -22,6 +22,7 @@ config KVM
>  	select PREEMPT_NOTIFIERS
>  	select ANON_INODES
>  	select HAVE_KVM_EVENTFD
> +	select HAVE_KVM_ARCH_DIRTY_LOG
>  
>  config KVM_BOOK3S_HANDLER
>  	bool
> diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
> index 94e597e..3835936 100644
> --- a/arch/powerpc/kvm/book3s.c
> +++ b/arch/powerpc/kvm/book3s.c
> @@ -781,7 +781,7 @@ int kvmppc_core_check_requests(struct kvm_vcpu *vcpu)
>  	return vcpu->kvm->arch.kvm_ops->check_requests(vcpu);
>  }
>  
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
>  {
>  	return kvm->arch.kvm_ops->get_dirty_log(kvm, log);
>  }
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index ab62109..50dd33d 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -1624,7 +1624,7 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
>  	return r;
>  }
>  
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
>  {
>  	return -ENOTSUPP;
>  }
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 0d45f6f..8afbe12 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -422,6 +422,7 @@ static inline bool kvm_is_error_hva(unsigned long addr)
>  }
>  
>  #define ASYNC_PF_PER_VCPU	64
> +struct kvm;
>  struct kvm_vcpu;
>  struct kvm_async_pf;
>  struct kvm_arch_async_pf {
> @@ -441,4 +442,5 @@ void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
>  
>  extern int sie64a(struct kvm_s390_sie_block *, u64 *);
>  extern char sie_exit;
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log);
>  #endif
> diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> index 10d529a..3ba07a7 100644
> --- a/arch/s390/kvm/Kconfig
> +++ b/arch/s390/kvm/Kconfig
> @@ -21,6 +21,7 @@ config KVM
>  	depends on HAVE_KVM
>  	select PREEMPT_NOTIFIERS
>  	select ANON_INODES
> +	select HAVE_KVM_ARCH_DIRTY_LOG
>  	select HAVE_KVM_CPU_RELAX_INTERCEPT
>  	select HAVE_KVM_EVENTFD
>  	select KVM_ASYNC_PF
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index b32c42c..95164e7 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -207,7 +207,7 @@ static void kvm_s390_sync_dirty_log(struct kvm *kvm,
>  /*
>   * Get (and clear) the dirty memory log for a memory slot.
>   */
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
> +int kvm_arch_vm_ioctl_get_dirty_log(struct kvm *kvm,
>  			       struct kvm_dirty_log *log)
>  {
>  	int r;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c5582c3..a603ca3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3569,92 +3569,6 @@ static int kvm_vm_ioctl_reinject(struct kvm *kvm,
>  	return 0;
>  }
>  
> -/**
> - * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
> - * @kvm: kvm instance
> - * @log: slot id and address to which we copy the log
> - *
> - * We need to keep it in mind that VCPU threads can write to the bitmap
> - * concurrently.  So, to avoid losing data, we keep the following order for
> - * each bit:
> - *
> - *   1. Take a snapshot of the bit and clear it if needed.
> - *   2. Write protect the corresponding page.
> - *   3. Flush TLB's if needed.
> - *   4. Copy the snapshot to the userspace.
> - *
> - * Between 2 and 3, the guest may write to the page using the remaining TLB
> - * entry.  This is not a problem because the page will be reported dirty at
> - * step 4 using the snapshot taken before and step 3 ensures that successive
> - * writes will be logged for the next call.
> - */
> -int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> -{
> -	int r;
> -	struct kvm_memory_slot *memslot;
> -	unsigned long n, i;
> -	unsigned long *dirty_bitmap;
> -	unsigned long *dirty_bitmap_buffer;
> -	bool is_dirty = false;
> -
> -	mutex_lock(&kvm->slots_lock);
> -
> -	r = -EINVAL;
> -	if (log->slot >= KVM_USER_MEM_SLOTS)
> -		goto out;
> -
> -	memslot = id_to_memslot(kvm->memslots, log->slot);
> -
> -	dirty_bitmap = memslot->dirty_bitmap;
> -	r = -ENOENT;
> -	if (!dirty_bitmap)
> -		goto out;
> -
> -	n = kvm_dirty_bitmap_bytes(memslot);
> -
> -	dirty_bitmap_buffer = dirty_bitmap + n / sizeof(long);
> -	memset(dirty_bitmap_buffer, 0, n);
> -
> -	spin_lock(&kvm->mmu_lock);
> -
> -	for (i = 0; i < n / sizeof(long); i++) {
> -		unsigned long mask;
> -		gfn_t offset;
> -
> -		if (!dirty_bitmap[i])
> -			continue;
> -
> -		is_dirty = true;
> -
> -		mask = xchg(&dirty_bitmap[i], 0);
> -		dirty_bitmap_buffer[i] = mask;
> -
> -		offset = i * BITS_PER_LONG;
> -		kvm_mmu_write_protect_pt_masked(kvm, memslot, offset, mask);
> -	}
> -
> -	spin_unlock(&kvm->mmu_lock);
> -
> -	/* See the comments in kvm_mmu_slot_remove_write_access(). */
> -	lockdep_assert_held(&kvm->slots_lock);
> -
> -	/*
> -	 * All the TLBs can be flushed out of mmu lock, see the comments in
> -	 * kvm_mmu_slot_remove_write_access().
> -	 */
> -	if (is_dirty)
> -		kvm_flush_remote_tlbs(kvm);
> -
> -	r = -EFAULT;
> -	if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
> -		goto out;
> -
> -	r = 0;
> -out:
> -	mutex_unlock(&kvm->slots_lock);
> -	return r;
> -}
> -
>  int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_event,
>  			bool line_status)
>  {
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 820fc2e..2f3822b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -606,6 +606,9 @@ int kvm_get_dirty_log(struct kvm *kvm,
>  int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
>  				struct kvm_dirty_log *log);
>  
> +void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
> +	struct kvm_memory_slot *slot, gfn_t gfn_offset, unsigned long mask);
> +
>  int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
>  			bool line_status);
>  long kvm_arch_vm_ioctl(struct file *filp,
> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
> index f1efaa5..975733f 100644
> --- a/virt/kvm/Kconfig
> +++ b/virt/kvm/Kconfig
> @@ -37,3 +37,6 @@ config KVM_VFIO
>  
>  config HAVE_KVM_ARCH_TLB_FLUSH_ALL
>         bool
> +
> +config HAVE_KVM_ARCH_DIRTY_LOG
> +       bool
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 258f3d9..51b90ca 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -442,6 +442,96 @@ static int kvm_init_mmu_notifier(struct kvm *kvm)
>  
>  #endif /* CONFIG_MMU_NOTIFIER && KVM_ARCH_WANT_MMU_NOTIFIER */
>  
> +/**
> + * kvm_vm_ioctl_get_dirty_log - get and clear the log of dirty pages in a slot
> + * @kvm: kvm instance
> + * @log: slot id and address to which we copy the log
> + *
> + * We need to keep it in mind that VCPU threads can write to the bitmap
> + * concurrently.  So, to avoid losing data, we keep the following order for
> + * each bit:
> + *
> + *   1. Take a snapshot of the bit and clear it if needed.
> + *   2. Write protect the corresponding page.
> + *   3. Flush TLB's if needed.
> + *   4. Copy the snapshot to the userspace.
> + *
> + * Between 2 and 3, the guest may write to the page using the remaining TLB
> + * entry.  This is not a problem because the page will be reported dirty at
> + * step 4 using the snapshot taken before and step 3 ensures that successive
> + * writes will be logged for the next call.
> + */
> +int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
> +{
> +#ifdef CONFIG_HAVE_KVM_ARCH_DIRTY_LOG
> +	return kvm_arch_vm_ioctl_get_dirty_log(kvm, log);
> +#else
> +	int r;
> +	struct kvm_memory_slot *memslot;
> +	unsigned long n, i;
> +	unsigned long *dirty_bitmap;
> +	unsigned long *dirty_bitmap_buffer;
> +	bool is_dirty = false;
> +
> +	mutex_lock(&kvm->slots_lock);
> +
> +	r = -EINVAL;
> +	if (log->slot >= KVM_USER_MEM_SLOTS)
> +		goto out;
> +
> +	memslot = id_to_memslot(kvm->memslots, log->slot);
> +
> +	dirty_bitmap = memslot->dirty_bitmap;
> +	r = -ENOENT;
> +	if (!dirty_bitmap)
> +		goto out;
> +
> +	n = kvm_dirty_bitmap_bytes(memslot);
> +
> +	dirty_bitmap_buffer = dirty_bitmap + n / sizeof(long);
> +	memset(dirty_bitmap_buffer, 0, n);
> +
> +	spin_lock(&kvm->mmu_lock);
> +
> +	for (i = 0; i < n / sizeof(long); i++) {
> +		unsigned long mask;
> +		gfn_t offset;
> +
> +		if (!dirty_bitmap[i])
> +			continue;
> +
> +		is_dirty = true;
> +
> +		mask = xchg(&dirty_bitmap[i], 0);
> +		dirty_bitmap_buffer[i] = mask;
> +
> +		offset = i * BITS_PER_LONG;
> +		kvm_mmu_write_protect_pt_masked(kvm, memslot, offset, mask);
> +	}
> +
> +	spin_unlock(&kvm->mmu_lock);
> +
> +	/* See the comments in kvm_mmu_slot_remove_write_access(). */
> +	lockdep_assert_held(&kvm->slots_lock);
> +
> +	/*
> +	 * All the TLBs can be flushed out of mmu lock, see the comments in
> +	 * kvm_mmu_slot_remove_write_access().
> +	 */
> +	if (is_dirty)
> +		kvm_flush_remote_tlbs(kvm);
> +
> +	r = -EFAULT;
> +	if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
> +		goto out;
> +
> +	r = 0;
> +out:
> +	mutex_unlock(&kvm->slots_lock);
> +	return r;
> +#endif
> +}
> +
>  static void kvm_init_memslots_id(struct kvm *kvm)
>  {
>  	int i;
> -- 
> 1.7.9.5
> 

Thanks,
-Christoffer