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[x86_64] fetch MMIO fault instructions across guest pages safely #406

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[x86_64] fetch MMIO fault instructions across guest pages safely #406

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21 changes: 20 additions & 1 deletion src/arch/x86_64/cpu.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,7 @@ pub struct ArchCpu {
// guest_regs and host_stack_top should always be at first.
guest_regs: GeneralRegisters,
host_stack_top: u64,
guest_cr2: usize,
pub cpuid: usize,
pub virt_lapic: VirtLocalApic,
vmx_on: bool,
Expand All @@ -192,6 +193,7 @@ impl ArchCpu {
Self {
guest_regs: GeneralRegisters::default(),
host_stack_top: 0,
guest_cr2: 0,
cpuid,
virt_lapic: VirtLocalApic::new(),
vmx_on: false,
Expand All @@ -207,6 +209,10 @@ impl ArchCpu {
Ok(VmcsGuestNW::RIP.write(VmcsGuestNW::RIP.read()? + instr_len as usize)?)
}

pub fn set_guest_cr2(&mut self, addr: usize) {
self.guest_cr2 = addr;
}

pub fn cr(&self, cr_idx: usize) -> usize {
(|| -> HvResult<usize> {
Ok(match cr_idx {
Expand Down Expand Up @@ -589,7 +595,12 @@ impl ArchCpu {

fn vmexit_handler(&mut self) {
crate::arch::trap::handle_vmexit(self).unwrap();
if this_cpu_data().vcpu_state.is_running() {
let entry_event_pending = VmcsControl32::VMENTRY_INTERRUPTION_INFO_FIELD
.read()
.unwrap()
& (1 << 31)
!= 0;
if this_cpu_data().vcpu_state.is_running() && !entry_event_pending {
check_pending_vectors(self.cpuid);
}
}
Expand All @@ -603,14 +614,19 @@ impl ArchCpu {
asm!(
save_regs_to_stack!(),
"mov r15, rsp", // save temporary RSP to r15
"mov rax, cr2",
"mov [rsp + {guest_cr2}], rax",
"mov rdi, rsp", // set the first arg to RSP
"mov rsp, [rsp + {host_stack_top}]", // set RSP to host_stack_top
"call {vmexit_handler}", // call vmexit_handler
"mov rsp, r15", // load temporary RSP from r15
"mov rax, [rsp + {guest_cr2}]",
"mov cr2, rax",
restore_regs_from_stack!(),
"vmresume",
"jmp {failed}",
host_stack_top = const size_of::<GeneralRegisters>(),
guest_cr2 = const core::mem::offset_of!(ArchCpu, guest_cr2),
vmexit_handler = sym Self::vmexit_handler,
failed = sym Self::vmx_entry_failed,
options(noreturn),
Expand All @@ -622,10 +638,13 @@ impl ArchCpu {
asm!(
// "mov [rdi + {host_stack_top}], rsp", // save current RSP to host_stack_top
"mov rsp, rdi", // set RSP to guest regs area
"mov rax, [rsp + {guest_cr2}]",
"mov cr2, rax",
restore_regs_from_stack!(),
"vmlaunch",
"jmp {failed}",
// host_stack_top = const size_of::<GeneralRegisters>(),
guest_cr2 = const core::mem::offset_of!(ArchCpu, guest_cr2),
failed = sym Self::vmx_entry_failed,
options(noreturn),
)
Expand Down
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