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: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index e4d23193eba75abd2fd2d27b90ab87c689f26011..6ec97eff9563d6a84aa2bf86d0d635824efe8afe 100644 (file)
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -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;

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index f1233500f4dcf018e841c9fcf654c2c33bca88b9..7de9ddbc6af175713fcaa52be34beb31b474b82c 100644 (file)
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -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;
 

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3eb7695aaa733ff74834e928dc8cff9a601e4fde..afacbfb2e4825e4f11394332916f5413995dc801 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -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;

diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index dd777688d14a926debd4ccc8c998c6995697a03a..ccb35c22785e3ac8f5d14d52bb7279ca18d63e9b 100644 (file)
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -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);

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a26b069a6929e72a20f8dbbf4e17740438f0412f..11db44f4110eb7cf08e1bee03fbad13d40683f17 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -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 &&