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virtio-devices: Use const fn to compute PCI BAR offsets

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This is much less error-prone than manual computation.  No functional
change intended.

Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
This commit is contained in:
Demi Marie Obenour
2026-02-11 20:08:45 -05:00
committed by Bo Chen
parent 001adbe15a
commit f630694bb0
1 changed files with 25 additions and 7 deletions
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32
virtio-devices/src/transport/pci_device.rs
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@@ -231,28 +231,46 @@ impl PciSubclass for PciVirtioSubclass {
}
}
/// Max number of virtio queues Cloud Hypervisor supports.
/// This is set by the current size of the notification BAR.
const MAX_QUEUES: u64 = 0x400;
// Automatically compute the position of the next entry in the BAR.
// This handles alignment properly and is much less error-prone than
// manual calculation.
const fn next_bar_addr_align(offset: u64, size: u64, align: u64) -> u64 {
assert!(align >= 0x2000, "too small alignment for structure in BAR");
assert!(align.is_power_of_two(), "alignment must be a power of 2");
(offset + size).next_multiple_of(align)
}
// Same as next_bar_addr_align(), but with the default alignment (8K).
const fn next_bar_addr(offset: u64, size: u64) -> u64 {
next_bar_addr_align(offset, size, 0x2000)
}
// Allocate one bar for the structs pointed to by the capability structures.
// As per the PCI specification, because the same BAR shares MSI-X and non
// MSI-X structures, it is recommended to use 8KiB alignment for all those
// structures.
const COMMON_CONFIG_BAR_OFFSET: u64 = 0x0000;
const COMMON_CONFIG_SIZE: u64 = 56;
const ISR_CONFIG_BAR_OFFSET: u64 = 0x2000;
const ISR_CONFIG_BAR_OFFSET: u64 = next_bar_addr(COMMON_CONFIG_BAR_OFFSET, COMMON_CONFIG_SIZE);
const ISR_CONFIG_SIZE: u64 = 1;
const DEVICE_CONFIG_BAR_OFFSET: u64 = 0x4000;
const DEVICE_CONFIG_BAR_OFFSET: u64 = next_bar_addr(ISR_CONFIG_BAR_OFFSET, ISR_CONFIG_SIZE);
const DEVICE_CONFIG_SIZE: u64 = 0x1000;
const NOTIFICATION_BAR_OFFSET: u64 = 0x6000;
const NOTIFICATION_SIZE: u64 = 0x1000;
const MSIX_TABLE_BAR_OFFSET: u64 = 0x8000;
const NOTIFICATION_BAR_OFFSET: u64 = next_bar_addr(DEVICE_CONFIG_BAR_OFFSET, DEVICE_CONFIG_SIZE);
const NOTIFICATION_SIZE: u64 = MAX_QUEUES * NOTIFY_OFF_MULTIPLIER as u64;
const MSIX_TABLE_BAR_OFFSET: u64 = next_bar_addr(NOTIFICATION_BAR_OFFSET, NOTIFICATION_SIZE);
// The size is 256KiB because the table can hold up to 2048 entries, with each
// entry being 128 bits (4 DWORDS).
const MSIX_TABLE_SIZE: u64 = 0x40000;
const MSIX_PBA_BAR_OFFSET: u64 = 0x48000;
const MSIX_PBA_BAR_OFFSET: u64 = next_bar_addr(MSIX_TABLE_BAR_OFFSET, MSIX_TABLE_SIZE);
// The size is 2KiB because the Pending Bit Array has one bit per vector and it
// can support up to 2048 vectors.
const MSIX_PBA_SIZE: u64 = 0x800;
// The BAR size must be a power of 2.
const CAPABILITY_BAR_SIZE: u64 = 0x80000;
const CAPABILITY_BAR_SIZE: u64 = (MSIX_PBA_BAR_OFFSET + MSIX_PBA_SIZE).next_power_of_two();
const VIRTIO_COMMON_BAR_INDEX: usize = 0;
const VIRTIO_SHM_BAR_INDEX: usize = 2;