[PATCH] arm/arm64: KVM: Check for properly initialized timer on init

When the arch timer code fails to initialize (for example because the
memory mapped timer doesn't work, which is currently seen with the AEM
model), then KVM just continues happily with a final result that KVM
eventually does a NULL pointer dereference of the uninitialized cycle
counter.

Check directly for this in the init path and give the user a reasonable
error in this case.

Cc: Shih-Wei Li <redacted>
Signed-off-by: Christoffer Dall <redacted>
---
 virt/kvm/arm/arch_timer.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 27a1f63..5c12f53 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c

@@ -425,6 +425,11 @@ int kvm_timer_hyp_init(void)
 	info = arch_timer_get_kvm_info();
 	timecounter = &info->timecounter;
 
+	if (!timecounter->cc) {
+		kvm_err("arch_timer: uninitialized timecounter\n");
+		return -ENODEV;
+	}
+
 	if (info->virtual_irq <= 0) {
 		kvm_err("kvm_arch_timer: invalid virtual timer IRQ: %d\n",
 			info->virtual_irq);

-- 
2.9.0

On 05/12/16 09:32, Christoffer Dall wrote:

For consistency, I'll change the error message to say "kvm_arch_timer",
just like the below case.

Otherwise looks good to me. I'll queue it now.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

On Tue, Dec 06, 2016 at 11:25:42AM +0000, Marc Zyngier wrote:

On 05/12/16 09:32, Christoffer Dall wrote:

quoted

When the arch timer code fails to initialize (for example because the
memory mapped timer doesn't work, which is currently seen with the AEM
model), then KVM just continues happily with a final result that KVM
eventually does a NULL pointer dereference of the uninitialized cycle
counter.

Check directly for this in the init path and give the user a reasonable
error in this case.

Cc: Shih-Wei Li <redacted>
Signed-off-by: Christoffer Dall <redacted>
---
 virt/kvm/arm/arch_timer.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 27a1f63..5c12f53 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c

@@ -425,6 +425,11 @@ int kvm_timer_hyp_init(void)
 	info = arch_timer_get_kvm_info();
 	timecounter = &info->timecounter;
 
+	if (!timecounter->cc) {
+		kvm_err("arch_timer: uninitialized timecounter\n");

For consistency, I'll change the error message to say "kvm_arch_timer",
just like the below case.

No objections, only problem is that the patch you queued uses
kcm_arch_timer ;)

quoted

+		return -ENODEV;
+	}
+
 	if (info->virtual_irq <= 0) {
 		kvm_err("kvm_arch_timer: invalid virtual timer IRQ: %d\n",
 			info->virtual_irq);

Otherwise looks good to me. I'll queue it now.

Thanks,
-Christoffer

On 06/12/16 19:56, Christoffer Dall wrote:

On Tue, Dec 06, 2016 at 11:25:42AM +0000, Marc Zyngier wrote:

quoted

On 05/12/16 09:32, Christoffer Dall wrote:

quoted

When the arch timer code fails to initialize (for example because the
memory mapped timer doesn't work, which is currently seen with the AEM
model), then KVM just continues happily with a final result that KVM
eventually does a NULL pointer dereference of the uninitialized cycle
counter.

Check directly for this in the init path and give the user a reasonable
error in this case.

Cc: Shih-Wei Li <redacted>
Signed-off-by: Christoffer Dall <redacted>
---
 virt/kvm/arm/arch_timer.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 27a1f63..5c12f53 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c

@@ -425,6 +425,11 @@ int kvm_timer_hyp_init(void)
 	info = arch_timer_get_kvm_info();
 	timecounter = &info->timecounter;
 
+	if (!timecounter->cc) {
+		kvm_err("arch_timer: uninitialized timecounter\n");

For consistency, I'll change the error message to say "kvm_arch_timer",
just like the below case.

No objections, only problem is that the patch you queued uses
kcm_arch_timer ;)

Yeah, that's the new and upgraded version: Kernel Cryogenic Machine, it
freezes time ;-).

I'll fix that shortly, thanks for the heads up!

	M.
-- 
Jazz is not dead. It just smells funny...