Commit 9fc77441 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Marcelo Tosatti
Browse files

KVM: make processes waiting on vcpu mutex killable 



vcpu mutex can be held for unlimited time so
taking it with mutex_lock on an ioctl is wrong:
one process could be passed a vcpu fd and
call this ioctl on the vcpu used by another process,
it will then be unkillable until the owner exits.

Call mutex_lock_killable instead and return status.
Note: mutex_lock_interruptible would be even nicer,
but I am not sure all users are prepared to handle EINTR
from these ioctls. They might misinterpret it as an error.

Cleanup paths expect a vcpu that can't be used by
any userspace so this will always succeed - catch bugs
by calling BUG_ON.

Catch callers that don't check return state by adding
__must_check.

Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 7454766f

arch/x86/kvm/x86.c

+9 −3
Original line number Diff line number Diff line
@@ -6016,7 +6016,9 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu) 
	int r;



	vcpu->arch.mtrr_state.have_fixed = 1;

	vcpu_load(vcpu);

	r = vcpu_load(vcpu);

	if (r)

		return r;

	r = kvm_arch_vcpu_reset(vcpu);

	if (r == 0)

		r = kvm_mmu_setup(vcpu);
@@ -6027,9 +6029,11 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu) 


void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)

{

	int r;

	vcpu->arch.apf.msr_val = 0;



	vcpu_load(vcpu);

	r = vcpu_load(vcpu);

	BUG_ON(r);

	kvm_mmu_unload(vcpu);

	vcpu_put(vcpu);
@@ -6275,7 +6279,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 


static void kvm_unload_vcpu_mmu(struct kvm_vcpu *vcpu)

{

	vcpu_load(vcpu);

	int r;

	r = vcpu_load(vcpu);

	BUG_ON(r);

	kvm_mmu_unload(vcpu);

	vcpu_put(vcpu);

}

include/linux/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -408,7 +408,7 @@ static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i) 
int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id);

void kvm_vcpu_uninit(struct kvm_vcpu *vcpu);



void vcpu_load(struct kvm_vcpu *vcpu);

int __must_check vcpu_load(struct kvm_vcpu *vcpu);

void vcpu_put(struct kvm_vcpu *vcpu);



int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,

virt/kvm/kvm_main.c

+7 −3
Original line number Diff line number Diff line
@@ -131,11 +131,12 @@ bool kvm_is_mmio_pfn(pfn_t pfn) 
/*

 * Switches to specified vcpu, until a matching vcpu_put()

 */

void vcpu_load(struct kvm_vcpu *vcpu)

int vcpu_load(struct kvm_vcpu *vcpu)

{

	int cpu;



	mutex_lock(&vcpu->mutex);

	if (mutex_lock_killable(&vcpu->mutex))

		return -EINTR;

	if (unlikely(vcpu->pid != current->pids[PIDTYPE_PID].pid)) {

		/* The thread running this VCPU changed. */

		struct pid *oldpid = vcpu->pid;
@@ -148,6 +149,7 @@ void vcpu_load(struct kvm_vcpu *vcpu) 
	preempt_notifier_register(&vcpu->preempt_notifier);

	kvm_arch_vcpu_load(vcpu, cpu);

	put_cpu();

	return 0;

}



void vcpu_put(struct kvm_vcpu *vcpu)
@@ -1891,7 +1893,9 @@ static long kvm_vcpu_ioctl(struct file *filp, 
#endif





	vcpu_load(vcpu);

	r = vcpu_load(vcpu);

	if (r)

		return r;

	switch (ioctl) {

	case KVM_RUN:

		r = -EINVAL;

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