[PATCH]Try to make some code simplications allowed by the mutex use

[PATCH]Try to make some code simplications allowed by the mutex use

[Laurent Vivier]

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Try to make some code simplifications allowed by the use of a mutex instead of a
spinlock. As we can keep the lock longer, we don't have to release it and then
have to check if the environment has not been modified before re-taking it. We
can remove kvm->busy and kvm->memory_config_version.

Signed-off-by: Laurent Vivier <Laurent.Vivier-6ktuUTfB/bM@public.gmane.org>

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Index: kvm/drivers/kvm/kvm.h
===================================================================
--- kvm.orig/drivers/kvm/kvm.h	2007-08-30 13:40:10.000000000 +0200
+++ kvm/drivers/kvm/kvm.h	2007-08-30 13:40:13.000000000 +0200
@@ -407,8 +407,6 @@ struct kvm {
 	int n_free_mmu_pages;
 	struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
-	int memory_config_version;
-	int busy;
 	unsigned long rmap_overflow;
 	struct list_head vm_list;
 	struct file *filp;
Index: kvm/drivers/kvm/kvm_main.c
===================================================================
--- kvm.orig/drivers/kvm/kvm_main.c	2007-08-30 13:40:10.000000000 +0200
+++ kvm/drivers/kvm/kvm_main.c	2007-08-30 13:40:35.000000000 +0200
@@ -615,7 +615,6 @@ static int kvm_vm_ioctl_set_memory_regio
 	unsigned long i;
 	struct kvm_memory_slot *memslot;
 	struct kvm_memory_slot old, new;
-	int memory_config_version;
 
 	r = -EINVAL;
 	/* General sanity checks */
@@ -635,10 +634,8 @@ static int kvm_vm_ioctl_set_memory_regio
 	if (!npages)
 		mem->flags &= ~KVM_MEM_LOG_DIRTY_PAGES;
 
-raced:
 	mutex_lock(&kvm->lock);
 
-	memory_config_version = kvm->memory_config_version;
 	new = old = *memslot;
 
 	new.base_gfn = base_gfn;
@@ -661,11 +658,6 @@ raced:
 		      (base_gfn >= s->base_gfn + s->npages)))
 			goto out_unlock;
 	}
-	/*
-	 * Do memory allocations outside lock.  memory_config_version will
-	 * detect any races.
-	 */
-	mutex_unlock(&kvm->lock);
 
 	/* Deallocate if slot is being removed */
 	if (!npages)
@@ -682,14 +674,14 @@ raced:
 		new.phys_mem = vmalloc(npages * sizeof(struct page *));
 
 		if (!new.phys_mem)
-			goto out_free;
+			goto out_unlock;
 
 		memset(new.phys_mem, 0, npages * sizeof(struct page *));
 		for (i = 0; i < npages; ++i) {
 			new.phys_mem[i] = alloc_page(GFP_HIGHUSER
 						     | __GFP_ZERO);
 			if (!new.phys_mem[i])
-				goto out_free;
+				goto out_unlock;
 			set_page_private(new.phys_mem[i],0);
 		}
 	}
@@ -700,27 +692,14 @@ raced:
 
 		new.dirty_bitmap = vmalloc(dirty_bytes);
 		if (!new.dirty_bitmap)
-			goto out_free;
+			goto out_unlock;
 		memset(new.dirty_bitmap, 0, dirty_bytes);
 	}
 
-	mutex_lock(&kvm->lock);
-
-	if (memory_config_version != kvm->memory_config_version) {
-		mutex_unlock(&kvm->lock);
-		kvm_free_physmem_slot(&new, &old);
-		goto raced;
-	}
-
-	r = -EAGAIN;
-	if (kvm->busy)
-		goto out_unlock;
-
 	if (mem->slot >= kvm->nmemslots)
 		kvm->nmemslots = mem->slot + 1;
 
 	*memslot = new;
-	++kvm->memory_config_version;
 
 	kvm_mmu_slot_remove_write_access(kvm, mem->slot);
 	kvm_flush_remote_tlbs(kvm);
@@ -732,7 +711,6 @@ raced:
 
 out_unlock:
 	mutex_unlock(&kvm->lock);
-out_free:
 	kvm_free_physmem_slot(&new, &old);
 out:
 	return r;
@@ -751,12 +729,6 @@ static int kvm_vm_ioctl_get_dirty_log(st
 
 	mutex_lock(&kvm->lock);
 
-	/*
-	 * Prevent changes to guest memory configuration even while the lock
-	 * is not taken.
-	 */
-	++kvm->busy;
-	mutex_unlock(&kvm->lock);
 	r = -EINVAL;
 	if (log->slot >= KVM_MEMORY_SLOTS)
 		goto out;
@@ -777,18 +749,14 @@ static int kvm_vm_ioctl_get_dirty_log(st
 
 	/* If nothing is dirty, don't bother messing with page tables. */
 	if (any) {
-		mutex_lock(&kvm->lock);
 		kvm_mmu_slot_remove_write_access(kvm, log->slot);
 		kvm_flush_remote_tlbs(kvm);
 		memset(memslot->dirty_bitmap, 0, n);
-		mutex_unlock(&kvm->lock);
 	}
 
 	r = 0;
 
 out:
-	mutex_lock(&kvm->lock);
-	--kvm->busy;
 	mutex_unlock(&kvm->lock);
 	return r;
 }

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Re: [PATCH]Try to make some code simplications allowed by the mutex use

[Avi Kivity]

Laurent Vivier wrote:
> Try to make some code simplifications allowed by the use of a mutex instead of a
> spinlock. As we can keep the lock longer, we don't have to release it and then
> have to check if the environment has not been modified before re-taking it. We
> can remove kvm->busy and kvm->memory_config_version.
>
>   

Applied, thanks.

-- 
error compiling committee.c: too many arguments to function


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