Commit 535f7ef2 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: VMX: Move IRQ invocation to assembly subroutine 



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: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200915191505.10355-2-sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 09e3e2a1

arch/x86/kvm/vmx/vmenter.S

+34 −0
Original line number Diff line number Diff line
@@ -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)

arch/x86/kvm/vmx/vmx.c

+3 −30
Original line number Diff line number Diff line
@@ -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)

{