firecracker adjustments for v12

- Drop setting memory attributes to private (workaround was needed to
  get KVM to fault non-coco VMs through guest_memfd always)
- Drop no-kvmclock (we have a workaround patch now)
- Drop VM types (guest_memfd is now supported on all vm types).

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

src/firecracker/examples/uffd/fault_all_handler.rs

@@ -50,7 +50,7 @@ fn main() {
                 let are_we_faulted_yet = uffd_handler
                     .userfault_bitmap
                     .as_mut()
-                    .map_or(false, |bitmap| !bitmap.is_bit_set(bit));
+                    .is_some_and(|bitmap| !bitmap.is_bit_set(bit));
 
                 if are_we_faulted_yet {
                     // TODO: we currently ignore the result as we may attempt to

src/firecracker/examples/uffd/on_demand_handler.rs

@@ -119,10 +119,8 @@ fn main() {
                                         println!("uffdio_continue error: {:?}", err)
                                     });
                                 }
-                            } else {
-                                if !uffd_handler.serve_pf(addr.cast(), uffd_handler.page_size) {
-                                    deferred_events.push(event);
-                                }
+                            } else if !uffd_handler.serve_pf(addr.cast(), uffd_handler.page_size) {
+                                deferred_events.push(event);
                             }
                         }
                         userfaultfd::Event::Remove { start, end } => {

src/firecracker/examples/uffd/uffd_utils.rs

@@ -247,9 +247,10 @@ impl UffdHandler {
         match (&guest_memfd, &userfault_bitmap_memfd) {
             (Some(guestmem_file), Some(bitmap_file)) => {
                 let guest_memfd_addr =
-                    Some(Self::mmap_helper(size, guestmem_file.as_raw_fd()) as *mut u8);
+                    Some(Self::mmap_helper(size, guestmem_file.as_raw_fd()).cast::<u8>());
 
-                let bitmap_ptr = Self::mmap_helper(size, bitmap_file.as_raw_fd()) as *mut AtomicU64;
+                let bitmap_ptr =
+                    Self::mmap_helper(size, bitmap_file.as_raw_fd()).cast::<AtomicU64>();
 
                 // SAFETY: The bitmap pointer is valid and the size is correct.
                 let userfault_bitmap = Some(unsafe {
@@ -302,7 +303,7 @@ impl UffdHandler {
         let addr = addr as u64;
         for region in &self.mem_regions {
             if region.contains(addr) {
-                return addr - region.base_host_virt_addr + region.offset as u64;
+                return addr - region.base_host_virt_addr + region.offset;
             }
         }
 
@@ -606,7 +607,7 @@ impl Runtime {
     ) -> UffdHandler {
         let mut message_buf = vec![0u8; 1024];
         let mut iovecs = [libc::iovec {
-            iov_base: message_buf.as_mut_ptr() as *mut libc::c_void,
+            iov_base: message_buf.as_mut_ptr().cast::<libc::c_void>(),
             iov_len: message_buf.len(),
         }];
         let mut fds = [0; 3];
@@ -686,7 +687,7 @@ impl Runtime {
                 if pollfds[i].revents & libc::POLLIN != 0 {
                     nready -= 1;
                     if pollfds[i].fd == self.stream.as_raw_fd() {
-                        while let Some(fault_request) = uffd_msg_iter.next() {
+                        for fault_request in uffd_msg_iter.by_ref() {
                             let page_size = self.handler.page_size;
 
                             assert!(

src/vmm/src/arch/aarch64/vm.rs

@@ -8,14 +8,6 @@ use crate::arch::aarch64::gic::GicState;
 use crate::vstate::memory::{GuestMemoryExtension, GuestMemoryState};
 use crate::vstate::vm::{VmCommon, VmError};
 
-/// The VM type for this architecture that allows us to use guest_memfd. On ARM, all VMs
-/// support guest_memfd and no special type is needed (in fact, no concept of vm types really
-/// exists, and the correspoding field of the CREATE_VM ioctl determines IPA size instead,
-/// e.g. the size of the guest physical address space. This value cannot be hardcoded, hence
-/// `None` to let the `Vm` constructor now that just normal [`Kvm::create_vm`] should be called,
-/// which internally determines the preferred IPA size.
-pub const VM_TYPE_FOR_SECRET_FREEDOM: Option<u64> = None;
-
 /// Structure representing the current architecture's understand of what a "virtual machine" is.
 #[derive(Debug)]
 pub struct ArchVm {

src/vmm/src/arch/mod.rs

@@ -17,7 +17,7 @@ pub use aarch64::kvm::{Kvm, KvmArchError, OptionalCapabilities};
 #[cfg(target_arch = "aarch64")]
 pub use aarch64::vcpu::*;
 #[cfg(target_arch = "aarch64")]
-pub use aarch64::vm::{ArchVm, ArchVmError, VM_TYPE_FOR_SECRET_FREEDOM, VmState};
+pub use aarch64::vm::{ArchVm, ArchVmError, VmState};
 #[cfg(target_arch = "aarch64")]
 pub use aarch64::{
     ConfigurationError, MMIO_MEM_SIZE, MMIO_MEM_START, arch_memory_regions,
@@ -35,7 +35,7 @@ pub use x86_64::kvm::{Kvm, KvmArchError};
 #[cfg(target_arch = "x86_64")]
 pub use x86_64::vcpu::*;
 #[cfg(target_arch = "x86_64")]
-pub use x86_64::vm::{ArchVm, ArchVmError, VM_TYPE_FOR_SECRET_FREEDOM, VmState};
+pub use x86_64::vm::{ArchVm, ArchVmError, VmState};
 
 #[cfg(target_arch = "x86_64")]
 pub use crate::arch::x86_64::{

src/vmm/src/arch/x86_64/vm.rs

@@ -5,8 +5,7 @@ use std::fmt;
 
 use kvm_bindings::{
     KVM_CLOCK_TSC_STABLE, KVM_IRQCHIP_IOAPIC, KVM_IRQCHIP_PIC_MASTER, KVM_IRQCHIP_PIC_SLAVE,
-    KVM_PIT_SPEAKER_DUMMY, KVM_X86_SW_PROTECTED_VM, MsrList, kvm_clock_data, kvm_irqchip,
-    kvm_pit_config, kvm_pit_state2,
+    KVM_PIT_SPEAKER_DUMMY, MsrList, kvm_clock_data, kvm_irqchip, kvm_pit_config, kvm_pit_state2,
 };
 use kvm_ioctls::Cap;
 use serde::{Deserialize, Serialize};
@@ -47,9 +46,6 @@ pub enum ArchVmError {
     SetTssAddress(kvm_ioctls::Error),
 }
 
-/// The VM type for this architecture that allows us to use guest_memfd.
-pub const VM_TYPE_FOR_SECRET_FREEDOM: Option<u64> = Some(KVM_X86_SW_PROTECTED_VM as u64);
-
 /// Structure representing the current architecture's understand of what a "virtual machine" is.
 #[derive(Debug)]
 pub struct ArchVm {

src/vmm/src/builder.rs

@@ -68,7 +68,7 @@ use crate::vmm_config::snapshot::{LoadSnapshotParams, MemBackendType};
 use crate::vstate::kvm::Kvm;
 use crate::vstate::memory::{MaybeBounce, create_memfd};
 use crate::vstate::vcpu::{Vcpu, VcpuError};
-use crate::vstate::vm::{KVM_GMEM_NO_DIRECT_MAP, Vm};
+use crate::vstate::vm::{GUEST_MEMFD_FLAG_NO_DIRECT_MAP, GUEST_MEMFD_FLAG_SUPPORT_SHARED, Vm};
 use crate::{EventManager, Vmm, VmmError, device_manager};
 
 /// Errors associated with starting the instance.
@@ -238,11 +238,6 @@ pub fn build_microvm_for_boot(
 
     let secret_free = vm_resources.machine_config.secret_free;
 
-    #[cfg(target_arch = "x86_64")]
-    if secret_free {
-        boot_cmdline.insert_str("no-kvmclock")?;
-    }
-
     let (mut vmm, mut vcpus) = create_vmm_and_vcpus(
         instance_info,
         event_manager,
@@ -254,7 +249,10 @@ pub fn build_microvm_for_boot(
     let guest_memfd = match secret_free {
         true => Some(
             vmm.vm
-                .create_guest_memfd(vm_resources.memory_size(), KVM_GMEM_NO_DIRECT_MAP)
+                .create_guest_memfd(
+                    vm_resources.memory_size(),
+                    GUEST_MEMFD_FLAG_SUPPORT_SHARED | GUEST_MEMFD_FLAG_NO_DIRECT_MAP,
+                )
                 .map_err(VmmError::Vm)?,
         ),
         false => None,
@@ -268,9 +266,6 @@ pub fn build_microvm_for_boot(
         .register_memory_regions(guest_memory, None)
         .map_err(VmmError::Vm)?;
 
-    #[cfg(target_arch = "x86_64")]
-    vmm.vm.set_memory_private().map_err(VmmError::Vm)?;
-
     let entry_point = load_kernel(
         MaybeBounce::<_, 4096>::new_persistent(
             boot_config.kernel_file.try_clone().unwrap(),
@@ -531,18 +526,12 @@ pub fn build_microvm_from_snapshot(
     params: &LoadSnapshotParams,
     vm_resources: &mut VmResources,
 ) -> Result<Arc<Mutex<Vmm>>, BuildMicrovmFromSnapshotError> {
-    // TODO: take it from kvm-bindings when userfault support is merged upstream
-    const KVM_CAP_USERFAULT: u32 = 241;
-
     // Build Vmm.
     debug!("event_start: build microvm from snapshot");
 
     let secret_free = vm_resources.machine_config.secret_free;
 
-    let mut kvm_capabilities = microvm_state.kvm_state.kvm_cap_modifiers.clone();
-    if secret_free {
-        kvm_capabilities.push(KvmCapability::Add(KVM_CAP_USERFAULT));
-    }
+    let kvm_capabilities = microvm_state.kvm_state.kvm_cap_modifiers.clone();
 
     let (mut vmm, mut vcpus) = create_vmm_and_vcpus(
         instance_info,
@@ -556,7 +545,10 @@ pub fn build_microvm_from_snapshot(
     let guest_memfd = match secret_free {
         true => Some(
             vmm.vm
-                .create_guest_memfd(vm_resources.memory_size(), KVM_GMEM_NO_DIRECT_MAP)
+                .create_guest_memfd(
+                    vm_resources.memory_size(),
+                    GUEST_MEMFD_FLAG_SUPPORT_SHARED | GUEST_MEMFD_FLAG_NO_DIRECT_MAP,
+                )
                 .map_err(VmmError::Vm)?,
         ),
         false => None,
@@ -622,9 +614,6 @@ pub fn build_microvm_from_snapshot(
     vmm.uffd = uffd;
     vmm.uffd_socket = socket;
 
-    #[cfg(target_arch = "x86_64")]
-    vmm.vm.set_memory_private().map_err(VmmError::Vm)?;
-
     #[cfg(target_arch = "x86_64")]
     {
         // Scale TSC to match, extract the TSC freq from the state if specified

src/vmm/src/vstate/vm.rs

@@ -13,16 +13,16 @@ use std::path::Path;
 use std::sync::{Arc, Condvar, Mutex};
 
 use kvm_bindings::{
-    KVM_MEM_GUEST_MEMFD, KVM_MEM_LOG_DIRTY_PAGES, KVM_MEMORY_ATTRIBUTE_PRIVATE, KVMIO,
-    kvm_create_guest_memfd, kvm_memory_attributes, kvm_userspace_memory_region,
+    KVM_MEM_GUEST_MEMFD, KVM_MEM_LOG_DIRTY_PAGES, KVMIO, kvm_create_guest_memfd,
+    kvm_userspace_memory_region,
 };
 use kvm_ioctls::{Cap, VmFd};
 use vmm_sys_util::eventfd::EventFd;
 use vmm_sys_util::ioctl::ioctl_with_ref;
 use vmm_sys_util::ioctl_iow_nr;
 
+use crate::arch::host_page_size;
 pub use crate::arch::{ArchVm as Vm, ArchVmError, VmState};
-use crate::arch::{VM_TYPE_FOR_SECRET_FREEDOM, host_page_size};
 use crate::logger::info;
 use crate::persist::CreateSnapshotError;
 use crate::utils::u64_to_usize;
@@ -34,7 +34,8 @@ use crate::vstate::memory::{
 use crate::vstate::vcpu::VcpuError;
 use crate::{DirtyBitmap, Vcpu, mem_size_mib};
 
-pub(crate) const KVM_GMEM_NO_DIRECT_MAP: u64 = 1;
+pub(crate) const GUEST_MEMFD_FLAG_SUPPORT_SHARED: u64 = 1 << 0;
+pub(crate) const GUEST_MEMFD_FLAG_NO_DIRECT_MAP: u64 = 1 << 1;
 
 /// KVM userfault information
 #[derive(Copy, Clone, Default, Eq, PartialEq, Debug)]
@@ -137,14 +138,7 @@ impl Vm {
         const MAX_ATTEMPTS: u32 = 5;
         let mut attempt = 1;
         let fd = loop {
-            let create_result = if secret_free && VM_TYPE_FOR_SECRET_FREEDOM.is_some() {
-                kvm.fd
-                    .create_vm_with_type(VM_TYPE_FOR_SECRET_FREEDOM.unwrap())
-            } else {
-                kvm.fd.create_vm()
-            };
-
-            match create_result {
+            match kvm.fd.create_vm() {
                 Ok(fd) => break fd,
                 Err(e) if e.errno() == libc::EINTR && attempt < MAX_ATTEMPTS => {
                     info!("Attempt #{attempt} of KVM_CREATE_VM returned EINTR");
@@ -371,28 +365,6 @@ impl Vm {
         &self.common.guest_memory
     }
 
-    /// Sets the memory attributes on all guest_memfd-backed regions to private
-    pub fn set_memory_private(&self) -> Result<(), VmError> {
-        if !self.secret_free() {
-            return Ok(());
-        }
-
-        for region in self.guest_memory().iter() {
-            let attr = kvm_memory_attributes {
-                address: region.start_addr().0,
-                size: region.len(),
-                attributes: KVM_MEMORY_ATTRIBUTE_PRIVATE as u64,
-                ..Default::default()
-            };
-
-            self.fd()
-                .set_memory_attributes(attr)
-                .map_err(VmError::SetMemoryAttributes)?
-        }
-
-        Ok(())
-    }
-
     /// Resets the KVM dirty bitmap for each of the guest's memory regions.
     pub fn reset_dirty_bitmap(&self) {
         self.guest_memory()