[RESEND PATCH 0/2] arm/arm64: kvm: Disable branch profiling in HYP code

[RESEND PATCH 0/2] arm/arm64: kvm: Disable branch profiling in HYP code

[Julien Thierry]

[Resending for Christoffer and adding kvmarm to recipients]

Hi,

When enabling branch profiling, a lockup occurs at boot time, after
displaying: "kvm [1]: Hyp mode initialized successfully"

The issue is caused by the Hyp code getting instrumented and trying to
access unmapped code or data, which happens when trying to initialize EL2.

So it also seems like KVM is misleadingly announcing it was initialized and
yet gets stuck during initialization.

* First patch deals with printing the initialization message once KVM has
  fully initialized Hyp mode
* Second patch actually disables branch profiling instrumentation in Hyp
  code

Cheers,

Julien Thierry (2):
  arm/arm64: kvm: Move initialization completion message
  arm/arm64: kvm: Disable branch profiling in HYP code

 arch/arm/kvm/hyp/Makefile   |  2 +-
 arch/arm64/kvm/hyp/Makefile |  2 +-
 virt/kvm/arm/arm.c          | 31 ++++++++++++++-----------------
 3 files changed, 16 insertions(+), 19 deletions(-)

--
1.9.1

[RESEND PATCH 1/2] arm/arm64: kvm: Move initialization completion message

[Julien Thierry]

KVM is being a bit too optimistic, Hyp mode is said to be initialized
when Hyp segments have only been mapped.

Notify KVM's successful initialization only once it is really fully
initialized.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
---
 virt/kvm/arm/arm.c | 31 ++++++++++++++-----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index b9f68e4..95cba07 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1326,21 +1326,12 @@ static void teardown_hyp_mode(void)
 {
 	int cpu;

-	if (is_kernel_in_hyp_mode())
-		return;
-
 	free_hyp_pgds();
 	for_each_possible_cpu(cpu)
 		free_page(per_cpu(kvm_arm_hyp_stack_page, cpu));
 	hyp_cpu_pm_exit();
 }

-static int init_vhe_mode(void)
-{
-	kvm_info("VHE mode initialized successfully\n");
-	return 0;
-}
-
 /**
  * Inits Hyp-mode on all online CPUs
  */
@@ -1421,8 +1412,6 @@ static int init_hyp_mode(void)
 		}
 	}

-	kvm_info("Hyp mode initialized successfully\n");
-
 	return 0;

 out_err:
@@ -1456,6 +1445,7 @@ int kvm_arch_init(void *opaque)
 {
 	int err;
 	int ret, cpu;
+	bool in_hyp_mode;

 	if (!is_hyp_mode_available()) {
 		kvm_err("HYP mode not available\n");
@@ -1474,21 +1464,28 @@ int kvm_arch_init(void *opaque)
 	if (err)
 		return err;

-	if (is_kernel_in_hyp_mode())
-		err = init_vhe_mode();
-	else
+	in_hyp_mode = is_kernel_in_hyp_mode();
+
+	if (!in_hyp_mode) {
 		err = init_hyp_mode();
-	if (err)
-		goto out_err;
+		if (err)
+			goto out_err;
+	}

 	err = init_subsystems();
 	if (err)
 		goto out_hyp;

+	if (in_hyp_mode)
+		kvm_info("VHE mode initialized successfully\n");
+	else
+		kvm_info("Hyp mode initialized successfully\n");
+
 	return 0;

 out_hyp:
-	teardown_hyp_mode();
+	if (!in_hyp_mode)
+		teardown_hyp_mode();
 out_err:
 	teardown_common_resources();
 	return err;
--
1.9.1

[RESEND PATCH 2/2] arm/arm64: kvm: Disable branch profiling in HYP code

[Julien Thierry]

When HYP code runs into branch profiling code, it attempts to jump to
unmapped memory, causing a HYP Panic.

Disable the branch profiling for code designed to run at HYP mode.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: <stable@vger.kernel.org>
---
 arch/arm/kvm/hyp/Makefile   | 2 +-
 arch/arm64/kvm/hyp/Makefile | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kvm/hyp/Makefile b/arch/arm/kvm/hyp/Makefile
index 8679405..92eab1d 100644
--- a/arch/arm/kvm/hyp/Makefile
+++ b/arch/arm/kvm/hyp/Makefile
@@ -2,7 +2,7 @@
 # Makefile for Kernel-based Virtual Machine module, HYP part
 #

-ccflags-y += -fno-stack-protector
+ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING

 KVM=../../../../virt/kvm

diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
index 14c4e3b..48b0354 100644
--- a/arch/arm64/kvm/hyp/Makefile
+++ b/arch/arm64/kvm/hyp/Makefile
@@ -2,7 +2,7 @@
 # Makefile for Kernel-based Virtual Machine module, HYP part
 #

-ccflags-y += -fno-stack-protector
+ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING

 KVM=../../../../virt/kvm

--
1.9.1

Re: [RESEND PATCH 0/2] arm/arm64: kvm: Disable branch profiling in HYP code

[Christoffer Dall]

On Fri, Oct 20, 2017 at 12:34:15PM +0100, Julien Thierry wrote:
> [Resending for Christoffer and adding kvmarm to recipients]
> 
> Hi,
> 
> When enabling branch profiling, a lockup occurs at boot time, after
> displaying: "kvm [1]: Hyp mode initialized successfully"
> 
> The issue is caused by the Hyp code getting instrumented and trying to
> access unmapped code or data, which happens when trying to initialize EL2.
> 
> So it also seems like KVM is misleadingly announcing it was initialized and
> yet gets stuck during initialization.
> 
> * First patch deals with printing the initialization message once KVM has
>   fully initialized Hyp mode
> * Second patch actually disables branch profiling instrumentation in Hyp
>   code

Applied, thanks.

-Christoffer