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KVM: VMX: Move IRQ invocation to assembly subroutine

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Move the asm blob that invokes the appropriate IRQ handler after VM-Exit
into a proper subroutine.  Unconditionally create a stack frame in the
subroutine so that, as objtool sees things, the function has standard
stack behavior.  The dynamic stack adjustment makes using unwind hints
problematic.

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200915191505.10355-2-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-09-15 12:15:04 -07:00 committed by Paolo Bonzini
parent 09e3e2a1cc
commit 535f7ef2ab
2 changed files with 37 additions and 30 deletions
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34
arch/x86/kvm/vmx/vmenter.S
View File

@ -4,6 +4,7 @@
#include <asm/bitsperlong.h>
#include <asm/kvm_vcpu_regs.h>
#include <asm/nospec-branch.h>
#include <asm/segment.h>
#define WORD_SIZE (BITS_PER_LONG / 8)
@ -294,3 +295,36 @@ SYM_FUNC_START(vmread_error_trampoline)
ret
SYM_FUNC_END(vmread_error_trampoline)
SYM_FUNC_START(vmx_do_interrupt_nmi_irqoff)
/*
* Unconditionally create a stack frame, getting the correct RSP on the
* stack (for x86-64) would take two instructions anyways, and RBP can
* be used to restore RSP to make objtool happy (see below).
*/
push %_ASM_BP
mov %_ASM_SP, %_ASM_BP
#ifdef CONFIG_X86_64
/*
* Align RSP to a 16-byte boundary (to emulate CPU behavior) before
* creating the synthetic interrupt stack frame for the IRQ/NMI.
*/
and $-16, %rsp
push $__KERNEL_DS
push %rbp
#endif
pushf
push $__KERNEL_CS
CALL_NOSPEC _ASM_ARG1
/*
* "Restore" RSP from RBP, even though IRET has already unwound RSP to
* the correct value. objtool doesn't know the callee will IRET and,
* without the explicit restore, thinks the stack is getting walloped.
* Using an unwind hint is problematic due to x86-64's dynamic alignment.
*/
mov %_ASM_BP, %_ASM_SP
pop %_ASM_BP
ret
SYM_FUNC_END(vmx_do_interrupt_nmi_irqoff)

33
arch/x86/kvm/vmx/vmx.c
View File

@ -6323,6 +6323,8 @@ static void vmx_apicv_post_state_restore(struct kvm_vcpu *vcpu)
memset(vmx->pi_desc.pir, 0, sizeof(vmx->pi_desc.pir));
}
void vmx_do_interrupt_nmi_irqoff(unsigned long entry);
static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx)
{
u32 intr_info = vmx_get_intr_info(&vmx->vcpu);
@ -6344,10 +6346,6 @@ static void handle_exception_nmi_irqoff(struct vcpu_vmx *vmx)
static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
{
unsigned int vector;
unsigned long entry;
#ifdef CONFIG_X86_64
unsigned long tmp;
#endif
gate_desc *desc;
u32 intr_info = vmx_get_intr_info(vcpu);
@ -6357,36 +6355,11 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
vector = intr_info & INTR_INFO_VECTOR_MASK;
desc = (gate_desc *)host_idt_base + vector;
entry = gate_offset(desc);
kvm_before_interrupt(vcpu);
asm volatile(
#ifdef CONFIG_X86_64
"mov %%rsp, %[sp]\n\t"
"and $-16, %%rsp\n\t"
"push %[ss]\n\t"
"push %[sp]\n\t"
#endif
"pushf\n\t"
"push %[cs]\n\t"
CALL_NOSPEC
:
#ifdef CONFIG_X86_64
[sp]"=&r"(tmp),
#endif
ASM_CALL_CONSTRAINT
:
[thunk_target]"r"(entry),
#ifdef CONFIG_X86_64
[ss]"i"(__KERNEL_DS),
#endif
[cs]"i"(__KERNEL_CS)
);
vmx_do_interrupt_nmi_irqoff(gate_offset(desc));
kvm_after_interrupt(vcpu);
}
STACK_FRAME_NON_STANDARD(handle_external_interrupt_irqoff);
static void vmx_handle_exit_irqoff(struct kvm_vcpu *vcpu)
{