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Oct 17, 2025
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Unify register representation across hypervisors #907

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119 changes: 29 additions & 90 deletions src/hyperlight_host/src/hypervisor/gdb/hyperv_debug.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,9 +19,10 @@ use std::collections::HashMap;
use windows::Win32::System::Hypervisor::WHV_VP_EXCEPTION_CONTEXT;

use super::arch::{MAX_NO_OF_HW_BP, vcpu_stop_reason};
use super::{GuestDebug, SW_BP_SIZE, VcpuStopReason, X86_64Regs};
use super::{GuestDebug, SW_BP_SIZE, VcpuStopReason};
use crate::hypervisor::regs::{CommonFpu, CommonRegisters};
use crate::hypervisor::windows_hypervisor_platform::VMProcessor;
use crate::hypervisor::wrappers::{WHvDebugRegisters, WHvGeneralRegisters};
use crate::hypervisor::wrappers::WHvDebugRegisters;
use crate::{HyperlightError, Result, new_error};

/// KVM Debug struct
Expand Down Expand Up @@ -54,7 +55,7 @@ impl HypervDebug {
/// Returns the instruction pointer from the stopped vCPU
fn get_instruction_pointer(&self, vcpu_fd: &VMProcessor) -> Result<u64> {
let regs = vcpu_fd
.get_regs()
.regs()
.map_err(|e| new_error!("Could not retrieve registers from vCPU: {:?}", e))?;

Ok(regs.rip)
Expand Down Expand Up @@ -103,7 +104,7 @@ impl HypervDebug {
self.single_step = step;

let mut regs = vcpu_fd
.get_regs()
.regs()
.map_err(|e| new_error!("Could not get registers: {:?}", e))?;

// Set TF Flag to enable Traps
Expand All @@ -114,7 +115,7 @@ impl HypervDebug {
}

vcpu_fd
.set_general_purpose_registers(&regs)
.set_regs(&regs)
.map_err(|e| new_error!("Could not set guest registers: {:?}", e))?;

Ok(())
Expand Down Expand Up @@ -185,45 +186,17 @@ impl GuestDebug for HypervDebug {
self.sw_breakpoints.remove(addr)
}

fn read_regs(&self, vcpu_fd: &Self::Vcpu, regs: &mut X86_64Regs) -> Result<()> {
fn read_regs(&self, vcpu_fd: &Self::Vcpu) -> Result<(CommonRegisters, CommonFpu)> {
log::debug!("Read registers");
let vcpu_regs = vcpu_fd
.get_regs()
let regs = vcpu_fd
.regs()
.map_err(|e| new_error!("Could not read guest registers: {:?}", e))?;

regs.rax = vcpu_regs.rax;
regs.rbx = vcpu_regs.rbx;
regs.rcx = vcpu_regs.rcx;
regs.rdx = vcpu_regs.rdx;
regs.rsi = vcpu_regs.rsi;
regs.rdi = vcpu_regs.rdi;
regs.rbp = vcpu_regs.rbp;
regs.rsp = vcpu_regs.rsp;
regs.r8 = vcpu_regs.r8;
regs.r9 = vcpu_regs.r9;
regs.r10 = vcpu_regs.r10;
regs.r11 = vcpu_regs.r11;
regs.r12 = vcpu_regs.r12;
regs.r13 = vcpu_regs.r13;
regs.r14 = vcpu_regs.r14;
regs.r15 = vcpu_regs.r15;

regs.rip = vcpu_regs.rip;
regs.rflags = vcpu_regs.rflags;

// Fetch XMM from WHVP
if let Ok(fpu) = vcpu_fd.get_fpu() {
regs.xmm = [
fpu.xmm0, fpu.xmm1, fpu.xmm2, fpu.xmm3, fpu.xmm4, fpu.xmm5, fpu.xmm6, fpu.xmm7,
fpu.xmm8, fpu.xmm9, fpu.xmm10, fpu.xmm11, fpu.xmm12, fpu.xmm13, fpu.xmm14,
fpu.xmm15,
];
regs.mxcsr = fpu.mxcsr;
} else {
log::warn!("Failed to read FPU/XMM via WHVP for debug registers");
}
let fpu = vcpu_fd
.fpu()
.map_err(|e| new_error!("Could not read guest FPU registers: {:?}", e))?;

Ok(())
Ok((regs, fpu))
}

fn set_single_step(&mut self, vcpu_fd: &Self::Vcpu, enable: bool) -> Result<()> {
Expand All @@ -236,62 +209,28 @@ impl GuestDebug for HypervDebug {
.map_err(|_| HyperlightError::TranslateGuestAddress(gva))
}

fn write_regs(&self, vcpu_fd: &Self::Vcpu, regs: &X86_64Regs) -> Result<()> {
fn write_regs(
&self,
vcpu_fd: &Self::Vcpu,
regs: &CommonRegisters,
fpu: &CommonFpu,
) -> Result<()> {
log::debug!("Write registers");
let gprs = WHvGeneralRegisters {
rax: regs.rax,
rbx: regs.rbx,
rcx: regs.rcx,
rdx: regs.rdx,
rsi: regs.rsi,
rdi: regs.rdi,
rbp: regs.rbp,
rsp: regs.rsp,
r8: regs.r8,
r9: regs.r9,
r10: regs.r10,
r11: regs.r11,
r12: regs.r12,
r13: regs.r13,
r14: regs.r14,
r15: regs.r15,

rip: regs.rip,
rflags: regs.rflags,
};

vcpu_fd
.set_general_purpose_registers(&gprs)
.set_regs(regs)
.map_err(|e| new_error!("Could not write guest registers: {:?}", e))?;

// Load existing FPU state, replace XMM and MXCSR, and write it back.
let mut fpu = match vcpu_fd.get_fpu() {
Ok(f) => f,
Err(e) => {
return Err(new_error!("Could not write guest registers: {:?}", e));
}
};

fpu.xmm0 = regs.xmm[0];
fpu.xmm1 = regs.xmm[1];
fpu.xmm2 = regs.xmm[2];
fpu.xmm3 = regs.xmm[3];
fpu.xmm4 = regs.xmm[4];
fpu.xmm5 = regs.xmm[5];
fpu.xmm6 = regs.xmm[6];
fpu.xmm7 = regs.xmm[7];
fpu.xmm8 = regs.xmm[8];
fpu.xmm9 = regs.xmm[9];
fpu.xmm10 = regs.xmm[10];
fpu.xmm11 = regs.xmm[11];
fpu.xmm12 = regs.xmm[12];
fpu.xmm13 = regs.xmm[13];
fpu.xmm14 = regs.xmm[14];
fpu.xmm15 = regs.xmm[15];
fpu.mxcsr = regs.mxcsr;
// Only xmm and mxcsr is piped though in the given fpu, so only set those
let mut current_fpu: CommonFpu = vcpu_fd
.fpu()
.map_err(|e| new_error!("Could not read guest FPU registers: {:?}", e))?;
current_fpu.mxcsr = fpu.mxcsr;
current_fpu.xmm = fpu.xmm;

vcpu_fd
.set_fpu(&fpu)
.map_err(|e| new_error!("Could not write guest registers: {:?}", e))
.set_fpu(&current_fpu)
.map_err(|e| new_error!("Could not write guest FPU registers: {:?}", e))?;
Ok(())
}
}
100 changes: 27 additions & 73 deletions src/hyperlight_host/src/hypervisor/gdb/kvm_debug.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,12 +18,13 @@ use std::collections::HashMap;

use kvm_bindings::{
KVM_GUESTDBG_ENABLE, KVM_GUESTDBG_SINGLESTEP, KVM_GUESTDBG_USE_HW_BP, KVM_GUESTDBG_USE_SW_BP,
kvm_debug_exit_arch, kvm_guest_debug, kvm_regs,
kvm_debug_exit_arch, kvm_guest_debug,
};
use kvm_ioctls::VcpuFd;

use super::arch::{MAX_NO_OF_HW_BP, SW_BP_SIZE, vcpu_stop_reason};
use super::{GuestDebug, VcpuStopReason, X86_64Regs};
use super::{GuestDebug, VcpuStopReason};
use crate::hypervisor::regs::{CommonFpu, CommonRegisters};
use crate::{HyperlightError, Result, new_error};

/// KVM Debug struct
Expand Down Expand Up @@ -167,57 +168,29 @@ impl GuestDebug for KvmDebug {
self.sw_breakpoints.remove(addr)
}

fn read_regs(&self, vcpu_fd: &Self::Vcpu, regs: &mut X86_64Regs) -> Result<()> {
fn read_regs(&self, vcpu_fd: &Self::Vcpu) -> Result<(CommonRegisters, CommonFpu)> {
log::debug!("Read registers");
let vcpu_regs = vcpu_fd
let regs = vcpu_fd
.get_regs()
.map_err(|e| new_error!("Could not read guest registers: {:?}", e))?;

regs.rax = vcpu_regs.rax;
regs.rbx = vcpu_regs.rbx;
regs.rcx = vcpu_regs.rcx;
regs.rdx = vcpu_regs.rdx;
regs.rsi = vcpu_regs.rsi;
regs.rdi = vcpu_regs.rdi;
regs.rbp = vcpu_regs.rbp;
regs.rsp = vcpu_regs.rsp;
regs.r8 = vcpu_regs.r8;
regs.r9 = vcpu_regs.r9;
regs.r10 = vcpu_regs.r10;
regs.r11 = vcpu_regs.r11;
regs.r12 = vcpu_regs.r12;
regs.r13 = vcpu_regs.r13;
regs.r14 = vcpu_regs.r14;
regs.r15 = vcpu_regs.r15;

regs.rip = vcpu_regs.rip;
regs.rflags = vcpu_regs.rflags;

// Read XMM registers from FPU state
// note kvm get_fpu doesn't actually set or read the mxcsr value
// https://elixir.bootlin.com/linux/v6.16/source/arch/x86/kvm/x86.c#L12229
match vcpu_fd.get_fpu() {
Ok(fpu) => {
// Convert KVM XMM registers ([u8; 16] x 16) to [u128; 16]
regs.xmm = fpu.xmm.map(u128::from_le_bytes);
}
Err(e) => {
log::warn!("Failed to read FPU state for XMM registers: {:?}", e);
}
}
let fpu_data = vcpu_fd
.get_fpu()
.map_err(|e| new_error!("Could not read guest FPU registers: {:?}", e))?;
let mut fpu: CommonFpu = CommonFpu::from(&fpu_data);

// Read MXCSR from XSAVE (MXCSR is at byte offset 24 -> u32 index 6)
// 11.5.10 Mode-Specific XSAVE/XRSTOR State Management
match vcpu_fd.get_xsave() {
Ok(xsave) => {
regs.mxcsr = xsave.region[6];
fpu.mxcsr = xsave.region[6];
}
Err(e) => {
log::warn!("Failed to read XSAVE for MXCSR: {:?}", e);
}
}

Ok(())
Ok((CommonRegisters::from(&regs), fpu))
}

fn set_single_step(&mut self, vcpu_fd: &Self::Vcpu, enable: bool) -> Result<()> {
Expand All @@ -236,49 +209,30 @@ impl GuestDebug for KvmDebug {
}
}

fn write_regs(&self, vcpu_fd: &Self::Vcpu, regs: &X86_64Regs) -> Result<()> {
fn write_regs(
&self,
vcpu_fd: &Self::Vcpu,
regs: &CommonRegisters,
fpu: &CommonFpu,
) -> Result<()> {
log::debug!("Write registers");
let new_regs = kvm_regs {
rax: regs.rax,
rbx: regs.rbx,
rcx: regs.rcx,
rdx: regs.rdx,
rsi: regs.rsi,
rdi: regs.rdi,
rbp: regs.rbp,
rsp: regs.rsp,
r8: regs.r8,
r9: regs.r9,
r10: regs.r10,
r11: regs.r11,
r12: regs.r12,
r13: regs.r13,
r14: regs.r14,
r15: regs.r15,

rip: regs.rip,
rflags: regs.rflags,
};
let new_regs = regs.into();

vcpu_fd
.set_regs(&new_regs)
.map_err(|e| new_error!("Could not write guest registers: {:?}", e))?;

// load existing values and replace the xmm registers
let mut fpu = match vcpu_fd.get_fpu() {
Ok(fpu) => fpu,
Err(e) => {
return Err(new_error!("Could not write guest registers: {:?}", e));
}
};

// Convert XMM registers from [u128; 16] (our internal representation)
// to [[u8; 16]; 16] (KVM FPU representation) using little-endian byte order.
fpu.xmm = regs.xmm.map(u128::to_le_bytes);
// Only xmm and mxcsr is piped though in the given fpu, so only set those
let mut current_fpu: CommonFpu = (&vcpu_fd.get_fpu()?).into();
current_fpu.mxcsr = fpu.mxcsr;
current_fpu.xmm = fpu.xmm;
vcpu_fd
.set_fpu(&fpu)
.set_fpu(&(&current_fpu).into())
.map_err(|e| new_error!("Could not write guest registers: {:?}", e))?;

// Read XMM registers from FPU state
// note kvm get_fpu doesn't actually set or read the mxcsr value
// https://elixir.bootlin.com/linux/v6.16/source/arch/x86/kvm/x86.c#L12229
// Update MXCSR using XSAVE region entry 6 (MXCSR) if available.
let mut xsave = match vcpu_fd.get_xsave() {
Ok(xsave) => xsave,
Expand All @@ -287,7 +241,7 @@ impl GuestDebug for KvmDebug {
}
};

xsave.region[6] = regs.mxcsr;
xsave.region[6] = fpu.mxcsr;
unsafe {
vcpu_fd
.set_xsave(&xsave)
Expand Down
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