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fix(virtio/pci): map BARs only once #2572

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fix(virtio/pci): map BARs only once #2572

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9db3e15
fix(virtio/pci): map BARs only once
cagatay-y Jul 22, 2026
8c4524a
Merge branch 'main' into fix-bar-mapping
stlankes Jul 23, 2026
79de297
doc(virtio/msix): document why the MSI-X capability must be mappable
cagatay-y Jul 24, 2026
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14 changes: 10 additions & 4 deletions src/drivers/virtio/transport/pci.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@
//! [Virtio Over PCI Bus]: https://docs.oasis-open.org/virtio/virtio/v1.2/cs01/virtio-v1.2-cs01.html#x1-1150001

use alloc::vec::Vec;
use core::array;
use core::cell::LazyCell;
use core::ptr::{self, NonNull};

use memory_addresses::PhysAddr;
Expand Down Expand Up @@ -625,6 +627,10 @@ pub(crate) fn map_caps(device: &PciDevice<PciConfigRegion>) -> Result<UniCapsCol
#[cfg(target_arch = "x86_64")]
let mut msix_table = None;

let bar_mappings = array::from_fn::<_, 6, _>(|slot| {
LazyCell::new(move || device.memory_map_bar(u8::try_from(slot).unwrap(), true))
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});

// Reads all PCI capabilities, starting at the capabilities list pointer from the
// PCI device.
//
Expand All @@ -638,7 +644,7 @@ pub(crate) fn map_caps(device: &PciDevice<PciConfigRegion>) -> Result<UniCapsCol
continue;
}
let slot = cap.bar;
let Some((addr, size)) = device.memory_map_bar(slot, true) else {
let Some((addr, size)) = *bar_mappings[usize::from(slot)] else {
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continue;
};
let pci_cap = PciCap {
Expand Down Expand Up @@ -695,9 +701,9 @@ pub(crate) fn map_caps(device: &PciDevice<PciConfigRegion>) -> Result<UniCapsCol
#[cfg(target_arch = "x86_64")]
PciCapability::MsiX(mut msix_capability) => {
msix_capability.set_enabled(true, device.access());
let (base_addr, _) = device
.memory_map_bar(msix_capability.table_bar(), true)
.unwrap();
let (base_addr, _) = bar_mappings[usize::from(msix_capability.table_bar())].expect(
"the capability should provide a valid BAR ID and \"[t]he BAR [...] must map Memory Space\" (PCIe spec. 6.0 sec. 7.7.2) for the MSI-X capability",
);
let table_ptr = NonNull::slice_from_raw_parts(
NonNull::with_exposed_provenance(
core::num::NonZero::new(
Expand Down
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