KVM: Add generic support for dirty page logging (ba0513b5) · Commits · 戴 / test

include/linux/kvm_host.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -611,6 +611,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext);

		int kvm_get_dirty_log(struct kvm *kvm,
		struct kvm_dirty_log log, int is_dirty);

		int kvm_get_dirty_log_protect(struct kvm *kvm,
		struct kvm_dirty_log log, bool is_dirty);

		void kvm_arch_mmu_write_protect_pt_masked(struct kvm *kvm,
		struct kvm_memory_slot *slot,
		gfn_t gfn_offset,
		unsigned long mask);

		int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
		struct kvm_dirty_log *log);

virt/kvm/Kconfig

+6 −0

Original line number	Diff line number	Diff line
		@@ -40,3 +40,9 @@ config KVM_VFIO

		config HAVE_KVM_ARCH_TLB_FLUSH_ALL
		bool

		config HAVE_KVM_ARCH_DIRTY_LOG_PROTECT
		bool

		config KVM_GENERIC_DIRTYLOG_READ_PROTECT
		bool

virt/kvm/kvm_main.c

+80 −0

Original line number	Diff line number	Diff line
		@@ -995,6 +995,86 @@ out:
		}
		EXPORT_SYMBOL_GPL(kvm_get_dirty_log);

		#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
		/**
		* kvm_get_dirty_log_protect - get a snapshot of dirty pages, and if any pages
		* are dirty write protect them for next write.
		* @kvm: pointer to kvm instance
		* @log: slot id and address to which we copy the log
		* @is_dirty: flag set if any page is dirty
		*
		* We need to keep it in mind that VCPU threads can write to the bitmap
		* concurrently. So, to avoid losing track of dirty pages we keep the
		* following order:
		*
		* 1. Take a snapshot of the bit and clear it if needed.
		* 2. Write protect the corresponding page.
		* 3. Copy the snapshot to the userspace.
		* 4. Upon return caller flushes TLB's if needed.
		*
		* Between 2 and 4, the guest may write to the page using the remaining TLB
		* entry. This is not a problem because the page is reported dirty using
		* the snapshot taken before and step 4 ensures that writes done after
		* exiting to userspace will be logged for the next call.
		*
		*/
		int kvm_get_dirty_log_protect(struct kvm *kvm,
		struct kvm_dirty_log log, bool is_dirty)
		{
		struct kvm_memory_slot *memslot;
		int r, i;
		unsigned long n;
		unsigned long *dirty_bitmap;
		unsigned long *dirty_bitmap_buffer;

		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);
		*is_dirty = false;
		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_arch_mmu_write_protect_pt_masked(kvm, memslot, offset,
		mask);
		}

		spin_unlock(&kvm->mmu_lock);

		r = -EFAULT;
		if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
		goto out;

		r = 0;
		out:
		return r;
		}
		EXPORT_SYMBOL_GPL(kvm_get_dirty_log_protect);
		#endif

		bool kvm_largepages_enabled(void)
		{
		return largepages_enabled;

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