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KVM: VMX: Make VMREAD error path play nice with noinstr
Mark vmread_error_trampoline() as noinstr, and add a second trampoline for the CONFIG_CC_HAS_ASM_GOTO_OUTPUT=n case to enable instrumentation when handling VM-Fail on VMREAD. VMREAD is used in various noinstr flows, e.g. immediately after VM-Exit, and objtool rightly complains that the call to the error trampoline leaves a no-instrumentation section without annotating that it's safe to do so. vmlinux.o: warning: objtool: vmx_vcpu_enter_exit+0xc9: call to vmread_error_trampoline() leaves .noinstr.text section Note, strictly speaking, enabling instrumentation in the VM-Fail path isn't exactly safe, but if VMREAD fails the kernel/system is likely hosed anyways, and logging that there is a fatal error is more important than *maybe* encountering slightly unsafe instrumentation. Reported-by: Su Hui <suhui@nfschina.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20230721235637.2345403-2-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -303,10 +303,8 @@ SYM_FUNC_START(vmx_do_nmi_irqoff)
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VMX_DO_EVENT_IRQOFF call asm_exc_nmi_kvm_vmx
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SYM_FUNC_END(vmx_do_nmi_irqoff)
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.section .text, "ax"
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#ifndef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
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/**
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* vmread_error_trampoline - Trampoline from inline asm to vmread_error()
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* @field: VMCS field encoding that failed
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@ -335,7 +333,7 @@ SYM_FUNC_START(vmread_error_trampoline)
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mov 3*WORD_SIZE(%_ASM_BP), %_ASM_ARG2
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mov 2*WORD_SIZE(%_ASM_BP), %_ASM_ARG1
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call vmread_error
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call vmread_error_trampoline2
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/* Zero out @fault, which will be popped into the result register. */
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_ASM_MOV $0, 3*WORD_SIZE(%_ASM_BP)
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@ -357,6 +355,8 @@ SYM_FUNC_START(vmread_error_trampoline)
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SYM_FUNC_END(vmread_error_trampoline)
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#endif
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.section .text, "ax"
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SYM_FUNC_START(vmx_do_interrupt_irqoff)
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VMX_DO_EVENT_IRQOFF CALL_NOSPEC _ASM_ARG1
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SYM_FUNC_END(vmx_do_interrupt_irqoff)
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@ -441,14 +441,24 @@ do { \
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pr_warn_ratelimited(fmt); \
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} while (0)
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void vmread_error(unsigned long field, bool fault)
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noinline void vmread_error(unsigned long field)
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{
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if (fault)
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kvm_spurious_fault();
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else
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vmx_insn_failed("vmread failed: field=%lx\n", field);
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vmx_insn_failed("vmread failed: field=%lx\n", field);
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}
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#ifndef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
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noinstr void vmread_error_trampoline2(unsigned long field, bool fault)
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{
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if (fault) {
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kvm_spurious_fault();
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} else {
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instrumentation_begin();
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vmread_error(field);
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instrumentation_end();
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}
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}
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#endif
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noinline void vmwrite_error(unsigned long field, unsigned long value)
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{
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vmx_insn_failed("vmwrite failed: field=%lx val=%lx err=%u\n",
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@ -10,7 +10,7 @@
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#include "vmcs.h"
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#include "../x86.h"
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void vmread_error(unsigned long field, bool fault);
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void vmread_error(unsigned long field);
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void vmwrite_error(unsigned long field, unsigned long value);
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void vmclear_error(struct vmcs *vmcs, u64 phys_addr);
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void vmptrld_error(struct vmcs *vmcs, u64 phys_addr);
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@ -31,6 +31,13 @@ void invept_error(unsigned long ext, u64 eptp, gpa_t gpa);
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* void vmread_error_trampoline(unsigned long field, bool fault);
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*/
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extern unsigned long vmread_error_trampoline;
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/*
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* The second VMREAD error trampoline, called from the assembly trampoline,
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* exists primarily to enable instrumentation for the VM-Fail path.
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*/
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void vmread_error_trampoline2(unsigned long field, bool fault);
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#endif
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static __always_inline void vmcs_check16(unsigned long field)
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