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hypervisor: kvm: Introduce KvmMemorySlot to track guest_memfd per slot

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Replace the bare OwnedFd map (guest_memfds) with a KvmMemorySlot struct
wrapped in an Arc so it can later be shared with KvmVcpu. This is a
pure refactor with no functional change; KvmMemorySlot currently holds
only the guest_memfd OwnedFd.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Rob Bradford <rbradford@meta.com>
This commit is contained in:
Rob Bradford
2026-05-07 15:17:15 +01:00
parent 26ed2a98bc
commit ebeef03192
1 changed files with 20 additions and 12 deletions
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32
hypervisor/src/kvm/mod.rs
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@@ -557,6 +557,11 @@ struct KvmDirtyLogSlot {
guest_memfd: u32, guest_memfd: u32,
} }
#[allow(dead_code)]
struct KvmMemorySlot {
guest_memfd: OwnedFd,
}
/// Wrapper over KVM VM ioctls. /// Wrapper over KVM VM ioctls.
pub struct KvmVm { pub struct KvmVm {
fd: Arc<VmFd>, fd: Arc<VmFd>,
@@ -567,7 +572,7 @@ pub struct KvmVm {
#[cfg(all(feature = "sev_snp", target_arch = "x86_64"))] #[cfg(all(feature = "sev_snp", target_arch = "x86_64"))]
snp_guest_policy: std::sync::OnceLock<u64>, snp_guest_policy: std::sync::OnceLock<u64>,
dirty_log_slots: RwLock<HashMap<u32, KvmDirtyLogSlot>>, dirty_log_slots: RwLock<HashMap<u32, KvmDirtyLogSlot>>,
guest_memfds: Option<RwLock<HashMap<u32, OwnedFd>>>, memory_slots: Option<Arc<RwLock<HashMap<u32, KvmMemorySlot>>>>,
} }
impl KvmVm { impl KvmVm {
@@ -645,7 +650,7 @@ impl KvmVm {
&self, &self,
region: kvm_userspace_memory_region2, region: kvm_userspace_memory_region2,
) -> Result<(), errno::Error> { ) -> Result<(), errno::Error> {
if self.guest_memfds.is_some() { if self.memory_slots.is_some() {
// SAFETY: Safe as the caller guarantees that region is safe to map // SAFETY: Safe as the caller guarantees that region is safe to map
// the guest and is non-overlapping. // the guest and is non-overlapping.
unsafe { self.fd.set_user_memory_region2(region) } unsafe { self.fd.set_user_memory_region2(region) }
@@ -665,7 +670,7 @@ impl KvmVm {
/// Get flag for kvm_userspace_memory_region based on memfd support. /// Get flag for kvm_userspace_memory_region based on memfd support.
fn get_kvm_userspace_memory_region_flag(&self, flag: u32) -> u32 { fn get_kvm_userspace_memory_region_flag(&self, flag: u32) -> u32 {
flag | if self.guest_memfds.is_some() { flag | if self.memory_slots.is_some() {
KVM_MEM_GUEST_MEMFD KVM_MEM_GUEST_MEMFD
} else { } else {
0 0
@@ -1018,7 +1023,7 @@ impl vm::Vm for KvmVm {
// Create a per-region guest_memfd when supported. // Create a per-region guest_memfd when supported.
// Each region gets its own fd sized exactly to memory_size // Each region gets its own fd sized exactly to memory_size
#[cfg(feature = "sev_snp")] #[cfg(feature = "sev_snp")]
let guest_memfd = if let Some(memfds) = &self.guest_memfds { let guest_memfd = if let Some(slots) = &self.memory_slots {
// SAFETY: Safe because guest regions are guaranteed not to overlap. // SAFETY: Safe because guest regions are guaranteed not to overlap.
let fd = unsafe { let fd = unsafe {
OwnedFd::from_raw_fd( OwnedFd::from_raw_fd(
@@ -1031,7 +1036,10 @@ impl vm::Vm for KvmVm {
) )
}; };
let raw_fd = fd.as_raw_fd() as u32; let raw_fd = fd.as_raw_fd() as u32;
memfds.write().unwrap().insert(slot, fd); slots
.write()
.unwrap()
.insert(slot, KvmMemorySlot { guest_memfd: fd });
raw_fd raw_fd
} else { } else {
0 0
@@ -1084,7 +1092,7 @@ impl vm::Vm for KvmVm {
} }
#[cfg(feature = "sev_snp")] #[cfg(feature = "sev_snp")]
if self.guest_memfds.is_some() { if self.memory_slots.is_some() {
self.fd self.fd
.set_memory_attributes(kvm_memory_attributes { .set_memory_attributes(kvm_memory_attributes {
address: region.guest_phys_addr, address: region.guest_phys_addr,
@@ -1143,8 +1151,8 @@ impl vm::Vm for KvmVm {
} }
// Close the per-region guest_memfd if one was created for this slot // Close the per-region guest_memfd if one was created for this slot
if let Some(memfds) = &self.guest_memfds { if let Some(slots) = &self.memory_slots {
memfds.write().unwrap().remove(&slot); slots.write().unwrap().remove(&slot);
} }
Ok(()) Ok(())
@@ -1585,10 +1593,10 @@ impl hypervisor::Hypervisor for KvmHypervisor {
} }
#[allow(unused_mut)] #[allow(unused_mut)]
let mut guest_memfds = None; let mut memory_slots = None;
#[cfg(feature = "sev_snp")] #[cfg(feature = "sev_snp")]
if _config.sev_snp_enabled && fd.check_extension(Cap::GuestMemfd) { if _config.sev_snp_enabled && fd.check_extension(Cap::GuestMemfd) {
guest_memfds = Some(RwLock::new(HashMap::new())); memory_slots = Some(Arc::new(RwLock::new(HashMap::new())));
} }
#[cfg(feature = "sev_snp")] #[cfg(feature = "sev_snp")]
@@ -1622,7 +1630,7 @@ impl hypervisor::Hypervisor for KvmHypervisor {
sev_fd, sev_fd,
#[cfg(feature = "sev_snp")] #[cfg(feature = "sev_snp")]
snp_guest_policy: std::sync::OnceLock::new(), snp_guest_policy: std::sync::OnceLock::new(),
guest_memfds, memory_slots,
})) }))
} }
@@ -1631,7 +1639,7 @@ impl hypervisor::Hypervisor for KvmHypervisor {
Ok(Arc::new(KvmVm { Ok(Arc::new(KvmVm {
fd: Arc::new(fd), fd: Arc::new(fd),
dirty_log_slots: RwLock::new(HashMap::new()), dirty_log_slots: RwLock::new(HashMap::new()),
guest_memfds: None, memory_slots: None,
})) }))
} }
} }