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hypervisor, vmm: Fix aarch64 SVE register save/restore

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When SVE is enabled, KVM replaces the FPSIMD V-registers with wider
SVE Z-registers. Attempting to access the old FPSIMD offsets returns
EINVAL.

Fix by classifying each register from KVM_GET_REG_LIST as core, system,
or extended. Extended registers (currently SVE only) are saved as
generic `ExtendedReg` entries split into `pre_finalize_regs` (registers
like SVE VLS that must be written before `vcpu_finalize`) and
`extended_regs`. FPSIMD registers are only accessed when SVE is absent.
Unrecognized register families error immediately so future extensions
like SME fail clearly rather than silently losing state.

The snapshot is deserialized before vCPU init to make pre-finalize
register state available for the init -> VLS -> finalize ordering
required by KVM.

Signed-off-by: Ruben Hakobyan <hruben@meta.com>
This commit is contained in:
Ruben Hakobyan
2026-05-21 19:04:20 -07:00
committed by Rob Bradford
parent e390f0bdc1
commit 5c25d82f59
6 changed files with 165 additions and 45 deletions
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20
hypervisor/src/cpu.rs
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@@ -18,6 +18,8 @@ use {anyhow::anyhow, vm_memory::GuestAddress};
use crate::RegList;
#[cfg(target_arch = "aarch64")]
use crate::VcpuInit;
#[cfg(target_arch = "aarch64")]
use crate::arch::aarch64::ExtendedReg;
#[cfg(target_arch = "x86_64")]
use crate::arch::x86::{CpuIdEntry, FpuState, LapicState, MsrEntry, SpecialRegisters};
#[cfg(feature = "tdx")]
@@ -221,6 +223,16 @@ pub enum HypervisorCpuError {
#[error("Failed to set aarch64 core register")]
SetAarchCoreRegister(#[source] anyhow::Error),
///
/// Getting extended register error
///
#[error("Failed to get extended register")]
GetExtendedRegister(#[source] anyhow::Error),
///
/// Setting extended register error
///
#[error("Failed to set extended register")]
SetExtendedRegister(#[source] anyhow::Error),
///
/// Getting RISC-V 64-bit core register error
///
#[error("Failed to get riscv64 core register")]
@@ -460,6 +472,14 @@ pub trait Vcpu: Send + Sync {
#[cfg(target_arch = "aarch64")]
fn vcpu_finalize(&self, feature: i32) -> Result<()>;
///
/// Sets pre-finalize registers (e.g. SVE VLS).
/// Must be called after vcpu_init and before vcpu_finalize.
///
#[cfg(target_arch = "aarch64")]
fn set_pre_finalize_regs(&self, _regs: &[ExtendedReg]) -> Result<()> {
Ok(())
}
///
/// Gets the features that have been finalized for a given CPU.
///
#[cfg(target_arch = "aarch64")]