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hypervisor: kvm: preserve guest MTRR MSRs

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KVM_GET_MSR_INDEX_LIST does not consistently include all
guest-programmable MTRR MSRs.

During save/restore while booting, the VMM initially sets only
MSR_MTRRdefType, then guest firmware or other early boot code can
program additional MTRR state before the snapshot is taken. If those
MSRs are missing from the vCPU MSR buffer, snapshot omits part of the
guest's MTRR configuration and restore resumes with an incomplete
MTRR map.

Add the guest-programmable MTRR MSRs to the KVM MSR index list used
to build the vCPU MSR buffer so the existing snapshot/restore path
preserves the guest's MTRR state.

On-behalf-of: SAP leander.kohler@sap.com
Signed-off-by: Leander Kohler <leander.kohler@cyberus-technology.de>
This commit is contained in:
Leander Kohler
2026-03-20 13:07:10 +01:00
committed by Bo Chen
parent 676c0d320b
commit f7f9895d57
3 changed files with 62 additions and 3 deletions
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19
hypervisor/src/kvm/mod.rs
View File

@@ -70,7 +70,8 @@ pub use x86_64::{CpuId, ExtendedControlRegisters, MsrEntries, VcpuKvmState};
use crate::ClockData;
#[cfg(target_arch = "x86_64")]
use crate::arch::x86::{
CpuIdEntry, FpuState, LapicState, MsrEntry, NUM_IOAPIC_PINS, SpecialRegisters, XsaveState,
CpuIdEntry, FpuState, LapicState, MTRR_MSR_INDICES, MsrEntry, NUM_IOAPIC_PINS,
SpecialRegisters, XsaveState,
};
use crate::{CpuState, IoEventAddress, IrqRoutingEntry, MpState, StandardRegisters};
// aarch64 dependencies
@@ -1128,9 +1129,21 @@ impl KvmHypervisor {
/// Retrieve the list of MSRs supported by the hypervisor.
///
fn get_msr_list(&self) -> hypervisor::Result<MsrList> {
self.kvm
let mut indices = self
.kvm
.get_msr_index_list()
.map_err(|e| hypervisor::HypervisorError::GetMsrList(e.into()))
.map_err(|e| hypervisor::HypervisorError::GetMsrList(e.into()))?
.as_slice()
.to_vec();
// KVM_GET_MSR_INDEX_LIST does not include MTRR MSRs, but firmware may update them before an early boot snapshot.
indices.extend(MTRR_MSR_INDICES);
let mut msr_list = MsrList::new(indices.len())
.map_err(|e| hypervisor::HypervisorError::GetMsrList(e.into()))?;
msr_list.as_mut_slice().copy_from_slice(&indices);
Ok(msr_list)
}
}