RAMBlock: Add support of KVM private guest memfd

Add KVM guest_memfd support to RAMBlock so both normal hva based memory
and kvm guest memfd based private memory can be associated in one RAMBlock.

Introduce new flag RAM_GUEST_MEMFD. When it's set, it calls KVM ioctl to
create private guest_memfd during RAMBlock setup.

Allocating a new RAM_GUEST_MEMFD flag to instruct the setup of guest memfd
is more flexible and extensible than simply relying on the VM type because
in the future we may have the case that not all the memory of a VM need
guest memfd. As a benefit, it also avoid getting MachineState in memory
subsystem.

Note, RAM_GUEST_MEMFD is supposed to be set for memory backends of
confidential guests, such as TDX VM. How and when to set it for memory
backends will be implemented in the following patches.

Introduce memory_region_has_guest_memfd() to query if the MemoryRegion has
KVM guest_memfd allocated.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-ID: <20240320083945.991426-7-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 594ae9b..217f3fe 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -537,6 +537,8 @@ void kvm_mark_guest_state_protected(void);
  */
 bool kvm_hwpoisoned_mem(void);
 
+int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp);
+
 int kvm_set_memory_attributes_private(hwaddr start, uint64_t size);
 int kvm_set_memory_attributes_shared(hwaddr start, uint64_t size);