Commit 510958e9 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
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KVM: Force PPC to define its own rcuwait object 



Do not define/reference kvm_vcpu.wait if __KVM_HAVE_ARCH_WQP is true, and
instead force the architecture (PPC) to define its own rcuwait object.
Allowing common KVM to directly access vcpu->wait without a guard makes
it all too easy to introduce potential bugs, e.g. kvm_vcpu_block(),
kvm_vcpu_on_spin(), and async_pf_execute() all operate on vcpu->wait, not
the result of kvm_arch_vcpu_get_wait(), and so may do the wrong thing for
PPC.

Due to PPC's shenanigans with respect to callbacks and waits (it switches
to the virtual core's wait object at KVM_RUN!?!?), it's not clear whether
or not this fixes any bugs.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-5-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 6f390916

arch/powerpc/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -749,6 +749,7 @@ struct kvm_vcpu_arch { 
	u8 irq_pending; /* Used by XIVE to signal pending guest irqs */

	u32 last_inst;



	struct rcuwait wait;

	struct rcuwait *waitp;

	struct kvmppc_vcore *vcore;

	int ret;

arch/powerpc/kvm/powerpc.c

+2 −1
Original line number Diff line number Diff line
@@ -753,7 +753,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) 
	if (err)

		goto out_vcpu_uninit;



	vcpu->arch.waitp = &vcpu->wait;

	rcuwait_init(&vcpu->arch.wait);

	vcpu->arch.waitp = &vcpu->arch.wait;

	kvmppc_create_vcpu_debugfs(vcpu, vcpu->vcpu_id);

	return 0;

include/linux/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -314,7 +314,9 @@ struct kvm_vcpu { 
	struct mutex mutex;

	struct kvm_run *run;



#ifndef __KVM_HAVE_ARCH_WQP

	struct rcuwait wait;

#endif

	struct pid __rcu *pid;

	int sigset_active;

	sigset_t sigset;

virt/kvm/async_pf.c

+1 −1
Original line number Diff line number Diff line
@@ -85,7 +85,7 @@ static void async_pf_execute(struct work_struct *work) 


	trace_kvm_async_pf_completed(addr, cr2_or_gpa);



	rcuwait_wake_up(&vcpu->wait);

	rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu));



	mmput(mm);

	kvm_put_kvm(vcpu->kvm);

virt/kvm/kvm_main.c

+6 −3
Original line number Diff line number Diff line
@@ -422,7 +422,9 @@ static void kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id) 
	vcpu->kvm = kvm;

	vcpu->vcpu_id = id;

	vcpu->pid = NULL;

#ifndef __KVM_HAVE_ARCH_WQP

	rcuwait_init(&vcpu->wait);

#endif

	kvm_async_pf_vcpu_init(vcpu);



	vcpu->pre_pcpu = -1;
@@ -3284,6 +3286,7 @@ update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited) 
 */

void kvm_vcpu_block(struct kvm_vcpu *vcpu)

{

	struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);

	bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);

	ktime_t start, cur, poll_end;

	bool waited = false;
@@ -3322,7 +3325,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) 
	}





	prepare_to_rcuwait(&vcpu->wait);

	prepare_to_rcuwait(wait);

	for (;;) {

		set_current_state(TASK_INTERRUPTIBLE);
@@ -3332,7 +3335,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) 
		waited = true;

		schedule();

	}

	finish_rcuwait(&vcpu->wait);

	finish_rcuwait(wait);

	cur = ktime_get();

	if (waited) {

		vcpu->stat.generic.halt_wait_ns +=
@@ -3544,7 +3547,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode) 
				continue;

			if (vcpu == me)

				continue;

			if (rcuwait_active(&vcpu->wait) &&

			if (rcuwait_active(kvm_arch_vcpu_get_wait(vcpu)) &&

			    !vcpu_dy_runnable(vcpu))

				continue;

			if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&