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KVM: x86: Prevent starting PIT timers in the absence of irqchip support

PATCH Applied Jan Kiszka 2 participants 3 messages Dec 14, 2011 – Dec 21, 2011

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Jan Kiszka

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#0 lore raw

PATCH 1/2 KVM: x86: Prevent starting PIT timers in the absence of irqchip support

User space may create the PIT and forgets about setting up the irqchips. In that case, firing PIT IRQs will crash the host:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000128
IP: [<ffffffffa10f6280>] kvm_set_irq+0x30/0x170 [kvm]
...
Call Trace:
 [<ffffffffa11228c1>] pit_do_work+0x51/0xd0 [kvm]
 [<ffffffff81071431>] process_one_work+0x111/0x4d0
 [<ffffffff81071bb2>] worker_thread+0x152/0x340
 [<ffffffff81075c8e>] kthread+0x7e/0x90
 [<ffffffff815a4474>] kernel_thread_helper+0x4/0x10

Prevent this by checking the irqchip mode before starting a timer. We can't deny creating the PIT if the irqchips aren't set up yet as current user land expects this order to work.

Signed-off-by Jan Kiszka <[email protected]>

---

This is for stable, the next patch just a cleanup.

 arch/x86/kvm/i8254.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)
arch/x86/kvm/i8254.c +7 -3
index 76e3f1c..405f262 100644
@@ -338,11 +338,15 @@ static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
 		return HRTIMER_NORESTART;
 }
 
-static void create_pit_timer(struct kvm_kpit_state *ps, u32 val, int is_period)
+static void create_pit_timer(struct kvm *kvm, u32 val, int is_period)
 {
+	struct kvm_kpit_state *ps = &kvm->arch.vpit->pit_state;
 	struct kvm_timer *pt = &ps->pit_timer;
 	s64 interval;
 
+	if (!irqchip_in_kernel(kvm))
+		return;
+
 	interval = muldiv64(val, NSEC_PER_SEC, KVM_PIT_FREQ);
 
 	pr_debug("create pit timer, interval is %llu nsec\n", interval);

@@ -394,13 +398,13 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val)
         /* FIXME: enhance mode 4 precision */
 	case 4:
 		if (!(ps->flags & KVM_PIT_FLAGS_HPET_LEGACY)) {
-			create_pit_timer(ps, val, 0);
+			create_pit_timer(kvm, val, 0);
 		}
 		break;
 	case 2:
 	case 3:
 		if (!(ps->flags & KVM_PIT_FLAGS_HPET_LEGACY)){
-			create_pit_timer(ps, val, 1);
+			create_pit_timer(kvm, val, 1);
 		}
 		break;
 	default:
Signature · 1 line
1.7.3.4
author
#1 lore raw

PATCH 2/2 KVM: x86: Consolidate PIT legacy test

Move the test for KVM_PIT_FLAGS_HPET_LEGACY into create_pit_timer instead of replicating it on the caller site.

Signed-off-by Jan Kiszka <[email protected]>
---
 arch/x86/kvm/i8254.c |   10 +++-------
 1 files changed, 3 insertions(+), 7 deletions(-)
arch/x86/kvm/i8254.c +3 -7
index 405f262..d68f99d 100644
@@ -344,7 +344,7 @@ static void create_pit_timer(struct kvm *kvm, u32 val, int is_period)
 	struct kvm_timer *pt = &ps->pit_timer;
 	s64 interval;
 
-	if (!irqchip_in_kernel(kvm))
+	if (!irqchip_in_kernel(kvm) || ps->flags & KVM_PIT_FLAGS_HPET_LEGACY)
 		return;
 
 	interval = muldiv64(val, NSEC_PER_SEC, KVM_PIT_FREQ);

@@ -397,15 +397,11 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val)
 	case 1:
         /* FIXME: enhance mode 4 precision */
 	case 4:
-		if (!(ps->flags & KVM_PIT_FLAGS_HPET_LEGACY)) {
-			create_pit_timer(kvm, val, 0);
-		}
+		create_pit_timer(kvm, val, 0);
 		break;
 	case 2:
 	case 3:
-		if (!(ps->flags & KVM_PIT_FLAGS_HPET_LEGACY)){
-			create_pit_timer(kvm, val, 1);
-		}
+		create_pit_timer(kvm, val, 1);
 		break;
 	default:
 		destroy_pit_timer(kvm->arch.vpit);
Signature · 1 line
1.7.3.4
Applied
#2 lore raw

Re: [PATCH 2/2] KVM: x86: Consolidate PIT legacy test

Quoted 7 lines · Jan Kiszka

Move the test for KVM_PIT_FLAGS_HPET_LEGACY into create_pit_timer instead of replicating it on the caller site.

Signed-off-by Jan Kiszka <[email protected]>
---
 arch/x86/kvm/i8254.c |   10 +++-------
 1 files changed, 3 insertions(+), 7 deletions(-)

Applied, thanks.