[PATCH v6 08/22] KVM: Refactor error handling for setting memory region

Sean Christopherson
2020-02-18T21:09:09Z

Replace a big pile o' gotos with returns to make it more obvious what
error code is being returned, and to prepare for refactoring the
functional, i.e. post-checks, portion of __kvm_set_memory_region().

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
virt/kvm/kvm_main.c | 40 ++++++++++++++++++----------------------
1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 42ec4dac99b3..ca397992e879 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1005,34 +1005,33 @@ int __kvm_set_memory_region(struct kvm *kvm,

r = check_memory_region_flags(mem);
if (r)
- goto out;
+ return r;

- r = -EINVAL;
as_id = mem->slot >> 16;
id = (u16)mem->slot;

/* General sanity checks */
if (mem->memory_size & (PAGE_SIZE - 1))
- goto out;
+ return -EINVAL;
if (mem->guest_phys_addr & (PAGE_SIZE - 1))
- goto out;
+ return -EINVAL;
/* We can read the guest memory with __xxx_user() later on. */
if ((id < KVM_USER_MEM_SLOTS) &&
((mem->userspace_addr & (PAGE_SIZE - 1)) ||
!access_ok((void __user *)(unsigned long)mem->userspace_addr,
mem->memory_size)))
- goto out;
+ return -EINVAL;
if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
- goto out;
+ return -EINVAL;
if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
- goto out;
+ return -EINVAL;

slot = id_to_memslot(__kvm_memslots(kvm, as_id), id);
base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
npages = mem->memory_size >> PAGE_SHIFT;

if (npages > KVM_MEM_MAX_NR_PAGES)
- goto out;
+ return -EINVAL;

new = old = *slot;

@@ -1049,20 +1048,18 @@ int __kvm_set_memory_region(struct kvm *kvm,
if ((new.userspace_addr != old.userspace_addr) ||
(npages != old.npages) ||
((new.flags ^ old.flags) & KVM_MEM_READONLY))
- goto out;
+ return -EINVAL;

if (base_gfn != old.base_gfn)
change = KVM_MR_MOVE;
else if (new.flags != old.flags)
change = KVM_MR_FLAGS_ONLY;
- else { /* Nothing to change. */
- r = 0;
- goto out;
- }
+ else /* Nothing to change. */
+ return 0;
}
} else {
if (!old.npages)
- goto out;
+ return -EINVAL;

change = KVM_MR_DELETE;
new.base_gfn = 0;
@@ -1071,29 +1068,29 @@ int __kvm_set_memory_region(struct kvm *kvm,

if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
/* Check for overlaps */
- r = -EEXIST;
kvm_for_each_memslot(slot, __kvm_memslots(kvm, as_id)) {
if (slot->id == id)
continue;
if (!((base_gfn + npages <= slot->base_gfn) ||
(base_gfn >= slot->base_gfn + slot->npages)))
- goto out;
+ return -EEXIST;
}
}

- r = -ENOMEM;
-
/* Allocate/free page dirty bitmap as needed */
if (!(new.flags & KVM_MEM_LOG_DIRTY_PAGES))
new.dirty_bitmap = NULL;
else if (!new.dirty_bitmap) {
- if (kvm_create_dirty_bitmap(&new) < 0)
- goto out;
+ r = kvm_create_dirty_bitmap(&new);
+ if (r)
+ return r;
}

slots = kvzalloc(sizeof(struct kvm_memslots), GFP_KERNEL_ACCOUNT);
- if (!slots)
+ if (!slots) {
+ r = -ENOMEM;
goto out_bitmap;
+ }
memcpy(slots, __kvm_memslots(kvm, as_id), sizeof(struct kvm_memslots));

if ((change == KVM_MR_DELETE) || (change == KVM_MR_MOVE)) {
@@ -1144,7 +1141,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
out_bitmap:
if (new.dirty_bitmap && !old.dirty_bitmap)
kvm_destroy_dirty_bitmap(&new);
-out:
return r;
}
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
--
2.24.1