refactor: replace PAGE_SIZE with GUEST/HOST_PAGE_SIZE

Firecracker was assuming page sizes for both
host and guest are 4K. But they can differ, so
split into 2 values.

Signed-off-by: Egor Lazarchuk <[email protected]>

Author: ShadowCurse

src/vmm/src/arch/aarch64/mod.rs

@@ -94,7 +94,8 @@ pub fn initrd_load_addr(
     guest_mem: &GuestMemoryMmap,
     initrd_size: usize,
 ) -> Result<u64, ConfigurationError> {
-    let round_to_pagesize = |size| (size + (super::PAGE_SIZE - 1)) & !(super::PAGE_SIZE - 1);
+    let round_to_pagesize =
+        |size| (size + (super::GUEST_PAGE_SIZE - 1)) & !(super::GUEST_PAGE_SIZE - 1);
     match GuestAddress(get_fdt_addr(guest_mem)).checked_sub(round_to_pagesize(initrd_size) as u64) {
         Some(offset) => {
             if guest_mem.address_in_range(offset) {

src/vmm/src/arch/mod.rs

@@ -52,8 +52,11 @@ pub struct InitrdConfig {
     pub size: usize,
 }
 
-/// Default (smallest) memory page size for the supported architectures.
-pub const PAGE_SIZE: usize = 4096;
+/// Default page size for the guest OS.
+pub const GUEST_PAGE_SIZE: usize = 4096;
+
+/// Default page size for the host OS.
+pub const HOST_PAGE_SIZE: usize = 4096;
 
 impl fmt::Display for DeviceType {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

src/vmm/src/arch/x86_64/mod.rs

@@ -97,7 +97,7 @@ pub fn initrd_load_addr(
         return Err(ConfigurationError::InitrdAddress);
     }
 
-    let align_to_pagesize = |address| address & !(super::PAGE_SIZE - 1);
+    let align_to_pagesize = |address| address & !(super::GUEST_PAGE_SIZE - 1);
     Ok(align_to_pagesize(lowmem_size - initrd_size) as u64)
 }
 

src/vmm/src/builder.rs

@@ -1305,7 +1305,7 @@ pub(crate) mod tests {
         use crate::vstate::memory::GuestMemory;
         let image = make_test_bin();
 
-        let mem_size: usize = image.len() * 2 + crate::arch::PAGE_SIZE;
+        let mem_size: usize = image.len() * 2 + crate::arch::GUEST_PAGE_SIZE;
 
         let tempfile = TempFile::new().unwrap();
         let mut tempfile = tempfile.into_file();
@@ -1344,7 +1344,7 @@ pub(crate) mod tests {
         let tempfile = TempFile::new().unwrap();
         let mut tempfile = tempfile.into_file();
         tempfile.write_all(&image).unwrap();
-        let gm = single_region_mem_at(crate::arch::PAGE_SIZE as u64 + 1, image.len() * 2);
+        let gm = single_region_mem_at(crate::arch::GUEST_PAGE_SIZE as u64 + 1, image.len() * 2);
 
         let res = load_initrd(&gm, &mut tempfile);
         assert!(

src/vmm/src/devices/virtio/iov_deque.rs

@@ -6,7 +6,7 @@ use std::os::fd::AsRawFd;
 use libc::{c_int, c_void, iovec, off_t, size_t};
 use memfd;
 
-use crate::arch::PAGE_SIZE;
+use crate::arch::HOST_PAGE_SIZE;
 
 #[derive(Debug, thiserror::Error, displaydoc::Display)]
 pub enum IovDequeError {
@@ -79,8 +79,8 @@ pub enum IovDequeError {
 // ```
 //
 // This value must be a multiple of 256 because this is the maximum number of `iovec` can fit into
-// 1 memory page: 256 * sizeof(iovec) == 4096 == PAGE_SIZE. IovDeque only operates with `PAGE_SIZE`
-// granularity.
+// 1 memory page: 256 * sizeof(iovec) == 4096 == HOST_PAGE_SIZE. IovDeque only operates with
+// `HOST_PAGE_SIZE` granularity.
 #[derive(Debug)]
 pub struct IovDeque<const L: u16> {
     pub iov: *mut libc::iovec,
@@ -93,7 +93,7 @@ unsafe impl<const L: u16> Send for IovDeque<L> {}
 
 impl<const L: u16> IovDeque<L> {
     const BYTES: usize = L as usize * std::mem::size_of::<iovec>();
-    const _ASSERT: () = assert!(Self::BYTES % PAGE_SIZE == 0);
+    const _ASSERT: () = assert!(Self::BYTES % HOST_PAGE_SIZE == 0);
 
     /// Create a [`memfd`] object that represents a single physical page
     fn create_memfd() -> Result<memfd::Memfd, IovDequeError> {

src/vmm/src/devices/virtio/iovec.rs

@@ -815,13 +815,13 @@ mod verification {
     use vm_memory::VolatileSlice;
 
     use super::IoVecBuffer;
+    use crate::arch::GUEST_PAGE_SIZE;
     use crate::devices::virtio::iov_deque::IovDeque;
     // Redefine `IoVecBufferMut` and `IovDeque` with specific length. Otherwise
     // Rust will not know what to do.
     type IoVecBufferMutDefault = super::IoVecBufferMut<FIRECRACKER_MAX_QUEUE_SIZE>;
     type IovDequeDefault = IovDeque<FIRECRACKER_MAX_QUEUE_SIZE>;
 
-    use crate::arch::PAGE_SIZE;
     use crate::devices::virtio::queue::FIRECRACKER_MAX_QUEUE_SIZE;
 
     // Maximum memory size to use for our buffers. For the time being 1KB.
@@ -912,8 +912,8 @@ mod verification {
         // SAFETY: safe because the layout has non-zero size
         let mem = unsafe {
             std::alloc::alloc(std::alloc::Layout::from_size_align_unchecked(
-                2 * PAGE_SIZE,
-                PAGE_SIZE,
+                2 * GUEST_PAGE_SIZE,
+                GUEST_PAGE_SIZE,
             ))
         };
         IovDequeDefault {

src/vmm/src/gdb/target.rs

@@ -33,7 +33,7 @@ use vm_memory::{Bytes, GuestAddress, GuestMemoryError};
 use super::arch;
 #[cfg(target_arch = "aarch64")]
 use crate::arch::aarch64::vcpu::VcpuError as AarchVcpuError;
-use crate::arch::PAGE_SIZE;
+use crate::arch::GUEST_PAGE_SIZE;
 use crate::logger::{error, info};
 use crate::utils::u64_to_usize;
 use crate::vstate::vcpu::VcpuSendEventError;
@@ -396,7 +396,7 @@ impl MultiThreadBase for FirecrackerTarget {
             // Compute the amount space left in the page after the gpa
             let read_len = std::cmp::min(
                 data.len(),
-                PAGE_SIZE - (u64_to_usize(gpa) & (PAGE_SIZE - 1)),
+                GUEST_PAGE_SIZE - (u64_to_usize(gpa) & (GUEST_PAGE_SIZE - 1)),
             );
 
             vmm.guest_memory()
@@ -430,7 +430,7 @@ impl MultiThreadBase for FirecrackerTarget {
             // Compute the amount space left in the page after the gpa
             let write_len = std::cmp::min(
                 data.len(),
-                PAGE_SIZE - (u64_to_usize(gpa) & (PAGE_SIZE - 1)),
+                GUEST_PAGE_SIZE - (u64_to_usize(gpa) & (GUEST_PAGE_SIZE - 1)),
             );
 
             vmm.guest_memory()

src/vmm/src/vstate/vm.rs

@@ -593,7 +593,7 @@ pub(crate) mod tests {
         let res = vm.set_kvm_memory_regions(&gm, false);
         res.unwrap();
 
-        // Trying to set a memory region with a size that is not a multiple of PAGE_SIZE
+        // Trying to set a memory region with a size that is not a multiple of GUEST_PAGE_SIZE
         // will result in error.
         let gm = single_region_mem(0x10);
         let res = vm.set_kvm_memory_regions(&gm, false);