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always cover at least the first 4 GiB of physical memory #448

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Merged
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Jul 11, 2024
Merged

always cover at least the first 4 GiB of physical memory #448

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10 changes: 8 additions & 2 deletions common/src/legacy_memory_region.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -132,11 +132,17 @@ where
///
/// Useful for creating a mapping for all physical memory.
pub fn max_phys_addr(&self) -> PhysAddr {
self.original
let max = self
.original
.clone()
.map(|r| r.start() + r.len())
.max()
.unwrap()
.unwrap();

// Always cover at least the first 4 GiB of physical memory. That area
// contains useful MMIO regions (local APIC, I/O APIC, PCI bars) that
// we want to make accessible to the kernel even if no DRAM exists >4GiB.
cmp::max(max, PhysAddr::new(0x1_0000_0000))
}

/// Calculate the maximum number of regions produced by [Self::construct_memory_map]
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