KVM: Simplify memory allocation

The mutex->splinlock convertion alllows us to make some code simplifications.
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@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index ee9f8bdee75544b6dd05b0f8219537f75da89c59..351da40807c5e7c2523336a5f7aac1117652e1a1 100644 (file)
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -411,8 +411,6 @@ 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;

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 9dffbbea46a77ae720127ecbe8ee8e4b90b9f4da..8da13a462e3ce1867b0e84ddf952c8df755e7536 100644 (file)
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -679,7 +679,6 @@ static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
        unsigned long i;
        struct kvm_memory_slot *memslot;
        struct kvm_memory_slot old, new;
-       int memory_config_version;
 
        r = -EINVAL;
        /* General sanity checks */
@@ -699,10 +698,8 @@ static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
        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;
@@ -725,11 +722,6 @@ 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)
@@ -746,14 +738,14 @@ 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);
                }
        }
@@ -764,27 +756,14 @@ 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);
@@ -796,7 +775,6 @@ raced:
 
 out_unlock:
        mutex_unlock(&kvm->lock);
-out_free:
        kvm_free_physmem_slot(&new, &old);
 out:
        return r;
@@ -815,12 +793,6 @@ static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 
        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;
@@ -841,18 +813,14 @@ static int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
 
        /* 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;
 }