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hw: fix "hw: x86_64: clean up vCPU startup"

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Syncing the vCPU state with the VMM before the virtualization technology
was inititialized on the target CPU core may fail, such as on VMX where
the resulting `vmread` instructions will cause #UD faults.

Skip syncing the vCPU state when the vCPU isn't initialized
yet and sync the initial `Vcpu_state` from the VMM when the vCPU is
known to be initialized.

Issue #5474
This commit is contained in:
Benjamin Lamowski 2025-03-17 16:33:26 +01:00 committed by Norman Feske
parent 71e9b603a7
commit dd8b78575e
5 changed files with 40 additions and 71 deletions
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58
repos/base-hw/src/core/spec/x86_64/virtualization/hypervisor.h
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@ -1,58 +0,0 @@
/*
* \brief Interface between kernel and hypervisor
* \author Benjamin Lamowski
* \date 2022-10-14
*/
/*
* Copyright (C) 2022 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _SPEC__PC__VIRTUALIZATION_HYPERVISOR_H_
#define _SPEC__PC__VIRTUALIZATION_HYPERVISOR_H_
#include <base/stdint.h>
#include <base/log.h>
namespace Hypervisor {
using Call_arg = Genode::umword_t;
using Call_ret = Genode::umword_t;
inline void restore_state_for_entry(Call_arg regs, Call_arg fpu_context)
{
asm volatile(
"fxrstor (%[fpu_context]);"
"mov %[regs], %%rsp;"
"popq %%r8;"
"popq %%r9;"
"popq %%r10;"
"popq %%r11;"
"popq %%r12;"
"popq %%r13;"
"popq %%r14;"
"popq %%r15;"
"popq %%rax;"
"popq %%rbx;"
"popq %%rcx;"
"popq %%rdx;"
"popq %%rdi;"
"popq %%rsi;"
"popq %%rbp;"
"sti;" /* maybe enter the kernel to handle an external
interrupt that occured ... */
"nop;"
"cli;" /* ... otherwise, just disable interrupts again */
"jmp _kernel_entry;"
:
: [regs] "r"(regs), [fpu_context] "r"(fpu_context)
: "memory");
};
}
#endif /* _SPEC__PC__VIRTUALIZATION_HYPERVISOR_H_ */

16
repos/base-hw/src/core/spec/x86_64/virtualization/kernel/svm.cc
View File

@ -14,6 +14,7 @@
#include <base/internal/page_size.h>
#include <base/log.h>
#include <hw/spec/x86_64/x86_64.h>
#include <hw/memory_consts.h>
#include <kernel/cpu.h>
#include <platform.h>
#include <spec/x86_64/virtualization/svm.h>
@ -496,7 +497,7 @@ void Vmcb::switch_world(Core::Cpu::Context &regs, addr_t stack_start)
that occured ... */
"nop;"
"cli;" /* ... otherwise, just disable interrupts again */
"subq $568, %%rsp;" /* keep room for fpu and general-purpose registers */
"subq %[stack_offset], %%rsp;" /* keep room for fpu and general-purpose registers */
"pushq %[trap_vmexit];" /* make the stack point to trapno, the right place
to jump to _kernel_entry. We push 256 because
this is outside of the valid range for interrupts
@ -504,11 +505,12 @@ void Vmcb::switch_world(Core::Cpu::Context &regs, addr_t stack_start)
"jmp _kernel_entry;" /* jump to _kernel_entry to save the
GPRs without breaking any */
:
: [regs] "r" (&regs.r8),
[fpu_context] "r" (&regs.fpu_context()),
[guest_state] "r" (vcpu_data.phys_addr + get_page_size()),
[host_state] "r" (root_vmcb_phys),
[stack] "r" (stack_start),
[trap_vmexit] "i"(TRAP_VMEXIT)
: [regs] "r" (&regs.r8),
[fpu_context] "r" (&regs.fpu_context()),
[guest_state] "r" (vcpu_data.phys_addr + get_page_size()),
[host_state] "r" (root_vmcb_phys),
[stack] "r" (stack_start),
[stack_offset] "i" (Hw::Mm::KERNEL_STACK_ERRCODE_OFFSET),
[trap_vmexit] "i"(TRAP_VMEXIT)
: "rax", "memory");
}

24
repos/base-hw/src/core/spec/x86_64/virtualization/kernel/vm.cc
View File

@ -24,7 +24,6 @@
#include <kernel/main.h>
#include <hw/spec/x86_64/x86_64.h>
#include <virtualization/hypervisor.h>
#include <virtualization/svm.h>
#include <virtualization/vmx.h>
@ -77,6 +76,13 @@ void Vm::proceed()
_vcpu_context.initialize(_cpu(),
reinterpret_cast<addr_t>(_id.table));
_vcpu_context.tsc_aux_host = _cpu().id();
_vcpu_context.init_state = Board::Vcpu_context::Init_state::STARTED;
/*
* Sync the initial state from the VMM that was skipped due to
* the vCPU being uninitialized.
*/
_sync_from_vmm();
}
Cpu::Ia32_tsc_aux::write(
@ -161,6 +167,15 @@ void Vm::exception(Genode::Cpu_state &state)
void Vm::_sync_to_vmm()
{
/*
* If the vCPU isn't initialized, sync instructions such as vmread may fail.
* Just sync the startup exit and skip the rest of the synchronization.
*/
if (_vcpu_context.init_state != Board::Vcpu_context::Init_state::STARTED) {
_state.exit_reason = (unsigned) Board::EXIT_STARTUP;
return;
}
_vcpu_context.write_vcpu_state(_state);
/*
@ -173,6 +188,13 @@ void Vm::_sync_to_vmm()
void Vm::_sync_from_vmm()
{
/*
* Syncing the state to an unitialized vCPU may fail.
* The inial state from the VMM will be synced after vCPU initialization.
*/
if (_vcpu_context.init_state != Board::Vcpu_context::Init_state::STARTED)
return;
_vcpu_context.read_vcpu_state(_state);
}

8
repos/base-hw/src/core/spec/x86_64/virtualization/kernel/vmx.cc
View File

@ -14,6 +14,7 @@
#include <base/log.h>
#include <cpu/cpu_state.h>
#include <hw/spec/x86_64/x86_64.h>
#include <hw/memory_consts.h>
#include <kernel/cpu.h>
#include <platform.h>
#include <spec/x86_64/kernel/panic.h>
@ -363,10 +364,11 @@ void Vmcs::initialize(Kernel::Cpu &cpu, Genode::addr_t page_table_phys)
write(E_HOST_IA32_SYSENTER_EIP, reinterpret_cast<Genode::uint64_t>(&kernel_entry_push_trap));
/*
* Set the RSP to trapno, so that _kernel_entry will save the registers
* into the right fields.
* Set the RSP to a stack offset such that kernel_entry_push_trap pushes
* the `TRAP_VMEXIT` value to the right place for consumption by the
* subsequent jump to _kernel_entry.
*/
write(E_HOST_RSP, cpu.stack_start() - 568);
write(E_HOST_RSP, cpu.stack_start() - Hw::Mm::KERNEL_STACK_ERRCODE_OFFSET);
write(E_HOST_RIP, reinterpret_cast<Genode::uint64_t>(&kernel_entry_push_trap));
}

5
repos/base-hw/src/lib/hw/spec/64bit/memory_consts.s
View File

@ -16,8 +16,9 @@
#namespace Hw {
# namespace Mm {
HW_MM_KERNEL_START = 0xffffffc000000000
HW_MM_KERNEL_STACK_SIZE = 0x10000
HW_MM_KERNEL_START = 0xffffffc000000000
HW_MM_KERNEL_STACK_SIZE = 0x10000
HW_MM_KERNEL_STACK_ERRCODE_OFFSET = 568
HW_MM_CPU_LOCAL_MEMORY_AREA_START = 0xffffffe070000000
HW_MM_CPU_LOCAL_MEMORY_AREA_SIZE = 0x10000000