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Commit cd3ff653 authored by Joerg Roedel's avatar Joerg Roedel Committed by Avi Kivity
Browse files

KVM: SVM: Move INTR vmexit out of atomic code 



The nested SVM code emulates a #vmexit caused by a request
to open the irq window right in the request function. This
is a bug because the request function runs with preemption
and interrupts disabled but the #vmexit emulation might
sleep. This can cause a schedule()-while-atomic bug and is
fixed with this patch.

Signed-off-by: default avatarJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 8d23c466

arch/x86/kvm/svm.c

+25 −1
Original line number Diff line number Diff line
@@ -85,6 +85,9 @@ struct nested_state { 
	/* gpa pointers to the real vectors */

	u64 vmcb_msrpm;



	/* A VMEXIT is required but not yet emulated */

	bool exit_required;



	/* cache for intercepts of the guest */

	u16 intercept_cr_read;

	u16 intercept_cr_write;
@@ -1379,7 +1382,14 @@ static inline int nested_svm_intr(struct vcpu_svm *svm) 


	svm->vmcb->control.exit_code = SVM_EXIT_INTR;



	if (nested_svm_exit_handled(svm)) {

	if (svm->nested.intercept & 1ULL) {

		/*

		 * The #vmexit can't be emulated here directly because this

		 * code path runs with irqs and preemtion disabled. A

		 * #vmexit emulation might sleep. Only signal request for

		 * the #vmexit here.

		 */

		svm->nested.exit_required = true;

		nsvm_printk("VMexit -> INTR\n");

		return 1;

	}
@@ -2340,6 +2350,13 @@ static int handle_exit(struct kvm_vcpu *vcpu) 


	trace_kvm_exit(exit_code, svm->vmcb->save.rip);



	if (unlikely(svm->nested.exit_required)) {

		nested_svm_vmexit(svm);

		svm->nested.exit_required = false;



		return 1;

	}



	if (is_nested(svm)) {

		int vmexit;
@@ -2615,6 +2632,13 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) 
	u16 gs_selector;

	u16 ldt_selector;



	/*

	 * A vmexit emulation is required before the vcpu can be executed

	 * again.

	 */

	if (unlikely(svm->nested.exit_required))

		return;



	svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];

	svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP];

	svm->vmcb->save.rip = vcpu->arch.regs[VCPU_REGS_RIP];