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KVM: VMX: Handle NMI VM-Exits in noinstr region

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Move VMX's handling of NMI VM-Exits into vmx_vcpu_enter_exit() so that
the NMI is handled prior to leaving the safety of noinstr.  Handling the
NMI after leaving noinstr exposes the kernel to potential ordering
problems as an instrumentation-induced fault, e.g. #DB, #BP, #PF, etc.
will unblock NMIs when IRETing back to the faulting instruction.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221213060912.654668-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2022-12-13 06:09:12 +00:00
parent 4f76e86f7e
commit 11df586d77
4 changed files with 30 additions and 22 deletions
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4
arch/x86/kvm/vmx/vmcs.h
View File

@ -75,7 +75,7 @@ struct loaded_vmcs {
struct vmcs_controls_shadow controls_shadow; struct vmcs_controls_shadow controls_shadow;
}; };
static inline bool is_intr_type(u32 intr_info, u32 type) static __always_inline bool is_intr_type(u32 intr_info, u32 type)
{ {
const u32 mask = INTR_INFO_VALID_MASK | INTR_INFO_INTR_TYPE_MASK; const u32 mask = INTR_INFO_VALID_MASK | INTR_INFO_INTR_TYPE_MASK;
@ -146,7 +146,7 @@ static inline bool is_icebp(u32 intr_info)
return is_intr_type(intr_info, INTR_TYPE_PRIV_SW_EXCEPTION); return is_intr_type(intr_info, INTR_TYPE_PRIV_SW_EXCEPTION);
} }
static inline bool is_nmi(u32 intr_info) static __always_inline bool is_nmi(u32 intr_info)
{ {
return is_intr_type(intr_info, INTR_TYPE_NMI_INTR); return is_intr_type(intr_info, INTR_TYPE_NMI_INTR);
} }

8
arch/x86/kvm/vmx/vmenter.S
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@ -299,6 +299,10 @@ SYM_INNER_LABEL(vmx_vmexit, SYM_L_GLOBAL)
SYM_FUNC_END(__vmx_vcpu_run) SYM_FUNC_END(__vmx_vcpu_run)
SYM_FUNC_START(vmx_do_nmi_irqoff)
VMX_DO_EVENT_IRQOFF call asm_exc_nmi_kvm_vmx
SYM_FUNC_END(vmx_do_nmi_irqoff)
.section .text, "ax" .section .text, "ax"
@ -353,10 +357,6 @@ SYM_FUNC_START(vmread_error_trampoline)
SYM_FUNC_END(vmread_error_trampoline) SYM_FUNC_END(vmread_error_trampoline)
#endif #endif
SYM_FUNC_START(vmx_do_nmi_irqoff)
VMX_DO_EVENT_IRQOFF call asm_exc_nmi_kvm_vmx
SYM_FUNC_END(vmx_do_nmi_irqoff)
SYM_FUNC_START(vmx_do_interrupt_irqoff) SYM_FUNC_START(vmx_do_interrupt_irqoff)
VMX_DO_EVENT_IRQOFF CALL_NOSPEC _ASM_ARG1 VMX_DO_EVENT_IRQOFF CALL_NOSPEC _ASM_ARG1
SYM_FUNC_END(vmx_do_interrupt_irqoff) SYM_FUNC_END(vmx_do_interrupt_irqoff)

34
arch/x86/kvm/vmx/vmx.c
View File

@ -5170,8 +5170,13 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
vect_info = vmx->idt_vectoring_info; vect_info = vmx->idt_vectoring_info;
intr_info = vmx_get_intr_info(vcpu); intr_info = vmx_get_intr_info(vcpu);
/*
* Machine checks are handled by handle_exception_irqoff(), or by
* vmx_vcpu_run() if a #MC occurs on VM-Entry. NMIs are handled by
* vmx_vcpu_enter_exit().
*/
if (is_machine_check(intr_info) || is_nmi(intr_info)) if (is_machine_check(intr_info) || is_nmi(intr_info))
return 1; /* handled by handle_exception_nmi_irqoff() */ return 1;
/* /*
* Queue the exception here instead of in handle_nm_fault_irqoff(). * Queue the exception here instead of in handle_nm_fault_irqoff().
@ -6884,7 +6889,7 @@ static void handle_nm_fault_irqoff(struct kvm_vcpu *vcpu)
rdmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err); rdmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
} }
static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx) static void handle_exception_irqoff(struct vcpu_vmx *vmx)
{ {
u32 intr_info = vmx_get_intr_info(&vmx->vcpu); u32 intr_info = vmx_get_intr_info(&vmx->vcpu);
@ -6897,12 +6902,6 @@ static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx)
/* Handle machine checks before interrupts are enabled */ /* Handle machine checks before interrupts are enabled */
else if (is_machine_check(intr_info)) else if (is_machine_check(intr_info))
kvm_machine_check(); kvm_machine_check();
/* We need to handle NMIs before interrupts are enabled */
else if (is_nmi(intr_info)) {
kvm_before_interrupt(&vmx->vcpu, KVM_HANDLING_NMI);
vmx_do_nmi_irqoff();
kvm_after_interrupt(&vmx->vcpu);
}
} }
static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu) static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
@ -6932,7 +6931,7 @@ static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu)
if (vmx->exit_reason.basic == EXIT_REASON_EXTERNAL_INTERRUPT) if (vmx->exit_reason.basic == EXIT_REASON_EXTERNAL_INTERRUPT)
handle_external_interrupt_irqoff(vcpu); handle_external_interrupt_irqoff(vcpu);
else if (vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI) else if (vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI)
handle_exception_nmi_irqoff(vmx); handle_exception_irqoff(vmx);
} }
/* /*
@ -7194,6 +7193,18 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
vmx_enable_fb_clear(vmx); vmx_enable_fb_clear(vmx);
if (unlikely(vmx->fail))
vmx->exit_reason.full = 0xdead;
else
vmx->exit_reason.full = vmcs_read32(VM_EXIT_REASON);
if ((u16)vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI &&
is_nmi(vmx_get_intr_info(vcpu))) {
kvm_before_interrupt(vcpu, KVM_HANDLING_NMI);
vmx_do_nmi_irqoff();
kvm_after_interrupt(vcpu);
}
guest_state_exit_irqoff(); guest_state_exit_irqoff();
} }
@ -7335,12 +7346,9 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
vmx->idt_vectoring_info = 0; vmx->idt_vectoring_info = 0;
if (unlikely(vmx->fail)) { if (unlikely(vmx->fail))
vmx->exit_reason.full = 0xdead;
return EXIT_FASTPATH_NONE; return EXIT_FASTPATH_NONE;
}
vmx->exit_reason.full = vmcs_read32(VM_EXIT_REASON);
if (unlikely((u16)vmx->exit_reason.basic == EXIT_REASON_MCE_DURING_VMENTRY)) if (unlikely((u16)vmx->exit_reason.basic == EXIT_REASON_MCE_DURING_VMENTRY))
kvm_machine_check(); kvm_machine_check();

6
arch/x86/kvm/x86.h
View File

@ -382,13 +382,13 @@ enum kvm_intr_type {
KVM_HANDLING_NMI, KVM_HANDLING_NMI,
}; };
static inline void kvm_before_interrupt(struct kvm_vcpu *vcpu, static __always_inline void kvm_before_interrupt(struct kvm_vcpu *vcpu,
enum kvm_intr_type intr) enum kvm_intr_type intr)
{ {
WRITE_ONCE(vcpu->arch.handling_intr_from_guest, (u8)intr); WRITE_ONCE(vcpu->arch.handling_intr_from_guest, (u8)intr);
} }
static inline void kvm_after_interrupt(struct kvm_vcpu *vcpu) static __always_inline void kvm_after_interrupt(struct kvm_vcpu *vcpu)
{ {
WRITE_ONCE(vcpu->arch.handling_intr_from_guest, 0); WRITE_ONCE(vcpu->arch.handling_intr_from_guest, 0);
} }