[RFC v2 PATCH 06/13] KVM: Register/unregister memfd backed memslot

Chao Peng
2021-11-19T13:49:30Z

Signed-off-by: Yu Zhang <yu.c.zhang@linux.intel.com>
Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
virt/kvm/kvm_main.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 271cef8d1cd0..b8673490d301 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1426,7 +1426,7 @@ static void update_memslots(struct kvm_memslots *slots,
static int check_memory_region_flags(struct kvm *kvm,
const struct kvm_userspace_memory_region_ext *mem)
{
- u32 valid_flags = 0;
+ u32 valid_flags = KVM_MEM_FD;

if (!kvm->dirty_log_unsupported)
valid_flags |= KVM_MEM_LOG_DIRTY_PAGES;
@@ -1604,10 +1604,20 @@ static int kvm_set_memslot(struct kvm *kvm,
kvm_copy_memslots(slots, __kvm_memslots(kvm, as_id));
}

+ if (mem->flags & KVM_MEM_FD && change == KVM_MR_CREATE) {
+ r = kvm_memfd_register(kvm, mem, new);
+ if (r)
+ goto out_slots;
+ }
+
r = kvm_arch_prepare_memory_region(kvm, new, mem, change);
if (r)
goto out_slots;

+ if (mem->flags & KVM_MEM_FD && (r || change == KVM_MR_DELETE)) {
+ kvm_memfd_unregister(kvm, new);
+ }
+
update_memslots(slots, new, change);
slots = install_new_memslots(kvm, as_id, slots);

@@ -1683,10 +1693,12 @@ int __kvm_set_memory_region(struct kvm *kvm,
return -EINVAL;
if (mem->guest_phys_addr & (PAGE_SIZE - 1))
return -EINVAL;
- /* We can read the guest memory with __xxx_user() later on. */
if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
- (mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
- !access_ok((void __user *)(unsigned long)mem->userspace_addr,
+ (mem->userspace_addr != untagged_addr(mem->userspace_addr)))
+ return -EINVAL;
+ /* We can read the guest memory with __xxx_user() later on. */
+ if (!(mem->flags & KVM_MEM_FD) &&
+ !access_ok((void __user *)(unsigned long)mem->userspace_addr,
mem->memory_size))
return -EINVAL;
if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
@@ -1727,6 +1739,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
new.dirty_bitmap = NULL;
memset(&new.arch, 0, sizeof(new.arch));
} else { /* Modify an existing slot. */
+ /* Private memslots are immutable, they can only be deleted. */
+ if (mem->flags & KVM_MEM_FD && mem->private_fd >= 0)
+ return -EINVAL;
if ((new.userspace_addr != old.userspace_addr) ||
(new.npages != old.npages) ||
((new.flags ^ old.flags) & KVM_MEM_READONLY))
--
2.17.1