Re: [PATCH v1 2/2] kvm: arm64: handle single-step of userspace mmio instructions

From: Julien Thierry
Date: Fri Oct 06 2017 - 09:13:46 EST

On 06/10/17 12:39, Alex BennÃe wrote:
The system state of KVM when using userspace emulation is not complete
until we return into KVM_RUN. To handle mmio related updates we wait
until they have been committed and then schedule our KVM_EXIT_DEBUG.

I've introduced a new function kvm_arm_maybe_return_debug() to wrap up
the differences between arm/arm64 which is currently null for arm.

Signed-off-by: Alex BennÃe <alex.bennee@xxxxxxxxxx>
arch/arm/include/asm/kvm_host.h | 2 ++
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/kvm/debug.c | 21 +++++++++++++++++++++
arch/arm64/kvm/handle_exit.c | 9 +++------
virt/kvm/arm/arm.c | 2 +-
virt/kvm/arm/mmio.c | 3 ++-
6 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 4a879f6ff13b..aec943f6d123 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -285,6 +285,8 @@ static inline void kvm_arm_init_debug(void) {}
static inline void kvm_arm_setup_debug(struct kvm_vcpu *vcpu) {}
static inline void kvm_arm_clear_debug(struct kvm_vcpu *vcpu) {}
static inline void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu) {}
+static inline int kvm_arm_maybe_return_debug(struct kvm_vcpu *vcpu,
+ struct kvm_run *run) {}

This function should return 1.

int kvm_arm_vcpu_arch_set_attr(struct kvm_vcpu *vcpu,
struct kvm_device_attr *attr);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e923b58606e2..fa67d21662f6 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -369,6 +369,7 @@ void kvm_arm_init_debug(void);
void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);
void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu);
+int kvm_arm_maybe_return_debug(struct kvm_vcpu *vcpu, struct kvm_run *run);

I feel the name could be a little bit more explicit:

kvm_arm_trap_need_step_debug, kvm_arm_trap_step_return_debug, kvm_arm_trap_need_return_debug.

At least, I think it would be nice that the name reflect that this check is meant for emulated instructions.


Reviewed-by: Julien Thierry <julien.thierry@xxxxxxx>


Julien Thierry