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Rework fw_cfg and add bootorder entry #170

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fa3cd55
devices: Introduce `u16` and `u64` payloads to `fw_cfg`
scholzp Jun 1, 2026
8e253d9
devices: Add defined defaults to fw_cfg legacy items
scholzp Jun 1, 2026
f7ba097
vmm: Add bootindex to `DiskConfig`
scholzp Jun 5, 2026
03ab3c1
vmm: Allow generating open firmware device paths for virtio devices
scholzp Jun 5, 2026
7a2a2c1
vmm: Expose boot order items
scholzp Jun 5, 2026
ed98bd1
vmm: Populate `bootorder` times of `fw_cfg`
scholzp Jun 5, 2026
9ac85eb
vmm: Make default fw_cfg device not contain binary blobs
scholzp Jun 4, 2026
6c823a4
vmm: Implicitly add `FwCfgConfig` if none is present but required
scholzp Jun 3, 2026
c4ba2b5
X: Enable fw_cfg device for development
scholzp Jun 1, 2026
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63 changes: 61 additions & 2 deletions devices/src/legacy/fw_cfg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -79,12 +79,27 @@ pub const PORT_FW_CFG_WIDTH: u64 = 0x10;

const FW_CFG_SIGNATURE: u16 = 0x00;
const FW_CFG_ID: u16 = 0x01;
const FW_CFG_UUID: u16 = 0x02;
const FW_CFG_RAM_SIZE: u16 = 0x03;
const FW_CFG_NOGRAPHIC: u16 = 0x04;
const FW_CFG_NB_CPUS: u16 = 0x05;
const FW_CFG_MACHINE_ID: u16 = 0x06;
const FW_CFG_KERNEL_ADDR: u16 = 0x07;
const FW_CFG_KERNEL_SIZE: u16 = 0x08;
const FW_CFG_KERNEL_CMDLINE: u16 = 0x09;
const FW_CFG_INITRD_ADDR: u16 = 0x0a;
const FW_CFG_INITRD_SIZE: u16 = 0x0b;
const FW_CFG_BOOT_DEVICE: u16 = 0x0c;
const FW_CFG_NUMA: u16 = 0x0d;
const FW_CFG_BOOT_MENU: u16 = 0x0e;
const FW_CFG_MAX_CPUS: u16 = 0x0f;
const FW_CFG_KERNEL_ENTRY: u16 = 0x10;
const FW_CFG_KERNEL_DATA: u16 = 0x11;
const FW_CFG_INITRD_DATA: u16 = 0x12;
const FW_CFG_CMDLINE_ADDR: u16 = 0x13;
const FW_CFG_CMDLINE_SIZE: u16 = 0x14;
const FW_CFG_CMDLINE_DATA: u16 = 0x15;
const FW_CFG_SETUP_ADDR: u16 = 0x16;
const FW_CFG_SETUP_SIZE: u16 = 0x17;
const FW_CFG_SETUP_DATA: u16 = 0x18;
const FW_CFG_FILE_DIR: u16 = 0x19;
Expand Down Expand Up @@ -116,7 +131,9 @@ pub enum FwCfgContent {
Bytes(Vec<u8>),
Slice(&'static [u8]),
File(u64, File),
U64(u64),
U32(u32),
U16(u16),
}

struct FwCfgContentAccess<'a> {
Expand All @@ -139,10 +156,18 @@ impl Read for FwCfgContentAccess<'_> {
Some(mut s) => s.read(buf),
None => Err(ErrorKind::UnexpectedEof)?,
},
FwCfgContent::U64(n) => match n.to_le_bytes().get(self.offset as usize..) {
Some(mut s) => s.read(buf),
None => Err(ErrorKind::UnexpectedEof)?,
},
FwCfgContent::U32(n) => match n.to_le_bytes().get(self.offset as usize..) {
Some(mut s) => s.read(buf),
None => Err(ErrorKind::UnexpectedEof)?,
},
FwCfgContent::U16(n) => match n.to_le_bytes().get(self.offset as usize..) {
Some(mut s) => s.read(buf),
None => Err(ErrorKind::UnexpectedEof)?,
},
}
}
}
Expand All @@ -159,7 +184,9 @@ impl FwCfgContent {
FwCfgContent::Bytes(v) => v.len(),
FwCfgContent::File(offset, f) => (f.metadata()?.len() - offset) as usize,
FwCfgContent::Slice(s) => s.len(),
FwCfgContent::U64(n) => size_of_val(n),
FwCfgContent::U32(n) => size_of_val(n),
FwCfgContent::U16(n) => size_of_val(n),
};
u32::try_from(ret).map_err(|_| std::io::ErrorKind::InvalidInput.into())
}
Expand Down Expand Up @@ -419,10 +446,34 @@ impl FwCfg {
pub fn new(memory: GuestMemoryAtomic<GuestMemoryMmap<AtomicBitmap>>) -> FwCfg {
const DEFAULT_ITEM: FwCfgContent = FwCfgContent::Slice(&[]);
let mut known_items = [DEFAULT_ITEM; FW_CFG_KNOWN_ITEMS];
let file_buf = Vec::from(FwCfgFilesHeader { count_be: 0 }.as_mut_bytes());

known_items[FW_CFG_SIGNATURE as usize] = FwCfgContent::Slice(&FW_CFG_DMA_SIGNATURE);
known_items[FW_CFG_ID as usize] = FwCfgContent::Slice(&FW_CFG_FEATURE);
let file_buf = Vec::from(FwCfgFilesHeader { count_be: 0 }.as_mut_bytes());
known_items[FW_CFG_FILE_DIR as usize] = FwCfgContent::Bytes(file_buf);
known_items[FW_CFG_UUID as usize] = FwCfgContent::Bytes(Default::default()); /* TODO? */

@Coffeeri Coffeeri Jun 12, 2026

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What are all these TODO's? Do we need those?

known_items[FW_CFG_RAM_SIZE as usize] = FwCfgContent::U64(0); /* TODO? */
known_items[FW_CFG_NOGRAPHIC as usize] = FwCfgContent::U16(0); /* TODO? */
known_items[FW_CFG_NB_CPUS as usize] = FwCfgContent::U16(0); /* TODO? */
known_items[FW_CFG_MACHINE_ID as usize] = FwCfgContent::U16(0); /* TODO? */
known_items[FW_CFG_KERNEL_ADDR as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_KERNEL_SIZE as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_KERNEL_CMDLINE as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_INITRD_ADDR as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_INITRD_SIZE as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_BOOT_DEVICE as usize] = FwCfgContent::U16(0); /* TODO? */
known_items[FW_CFG_NUMA as usize] = FwCfgContent::Bytes(Default::default()); /* TODO? */
known_items[FW_CFG_BOOT_MENU as usize] = FwCfgContent::U16(0); /* TODO? */
known_items[FW_CFG_MAX_CPUS as usize] = FwCfgContent::U16(255); /* TODO? */
known_items[FW_CFG_KERNEL_ENTRY as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_KERNEL_DATA as usize] = FwCfgContent::Bytes(Default::default()); /* TODO? */
known_items[FW_CFG_INITRD_DATA as usize] = FwCfgContent::Bytes(Default::default()); /* TODO? */
known_items[FW_CFG_CMDLINE_ADDR as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_CMDLINE_SIZE as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_CMDLINE_DATA as usize] = FwCfgContent::Bytes(Default::default()); /* TODO? */
known_items[FW_CFG_SETUP_ADDR as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_SETUP_SIZE as usize] = FwCfgContent::U32(0); /* TODO? */
known_items[FW_CFG_SETUP_DATA as usize] = FwCfgContent::Bytes(Default::default()); /* TODO? */
known_items[FW_CFG_FILE_DIR as usize] = FwCfgContent::Bytes(file_buf); /* TODO? */

FwCfg {
selector: 0,
Expand Down Expand Up @@ -737,10 +788,18 @@ impl FwCfg {
FwCfgContent::File(o, f) => {
f.read_exact_at(data, o + offset as u64).ok()?;
}
FwCfgContent::U64(n) => {
let bytes = n.to_le_bytes();
data.copy_from_slice(&bytes[start..end]);
}
FwCfgContent::U32(n) => {
let bytes = n.to_le_bytes();
data.copy_from_slice(&bytes[start..end]);
}
FwCfgContent::U16(n) => {
let bytes = n.to_le_bytes();
data.copy_from_slice(&bytes[start..end]);
}
}
Some(size as u8)
}
Expand Down