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authorMark Rutland <mark.rutland@arm.com>2018-11-09 15:07:11 +0000
committerMarc Zyngier <marc.zyngier@arm.com>2018-12-18 14:11:37 +0000
commitbd7d95cafb499e24903b7d21f9eeb2c5208160c2 (patch)
tree854152408fc000dcb53d6256d8843d2656468506 /arch/arm64/kvm/handle_exit.c
parent0d640732dbebed0f10f18526de21652931f0b2f2 (diff)
downloadlwn-bd7d95cafb499e24903b7d21f9eeb2c5208160c2.tar.gz
lwn-bd7d95cafb499e24903b7d21f9eeb2c5208160c2.zip
arm64: KVM: Consistently advance singlestep when emulating instructions
When we emulate a guest instruction, we don't advance the hardware singlestep state machine, and thus the guest will receive a software step exception after a next instruction which is not emulated by the host. We bodge around this in an ad-hoc fashion. Sometimes we explicitly check whether userspace requested a single step, and fake a debug exception from within the kernel. Other times, we advance the HW singlestep state rely on the HW to generate the exception for us. Thus, the observed step behaviour differs for host and guest. Let's make this simpler and consistent by always advancing the HW singlestep state machine when we skip an instruction. Thus we can rely on the hardware to generate the singlestep exception for us, and never need to explicitly check for an active-pending step, nor do we need to fake a debug exception from the guest. Cc: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Christoffer Dall <christoffer.dall@arm.com> Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'arch/arm64/kvm/handle_exit.c')
-rw-r--r--arch/arm64/kvm/handle_exit.c14
1 files changed, 1 insertions, 13 deletions
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 35a81bebd02b..b0643f9c4873 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -229,13 +229,6 @@ static int handle_trap_exceptions(struct kvm_vcpu *vcpu, struct kvm_run *run)
handled = exit_handler(vcpu, run);
}
- /*
- * kvm_arm_handle_step_debug() sets the exit_reason on the kvm_run
- * structure if we need to return to userspace.
- */
- if (handled > 0 && kvm_arm_handle_step_debug(vcpu, run))
- handled = 0;
-
return handled;
}
@@ -269,12 +262,7 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
case ARM_EXCEPTION_IRQ:
return 1;
case ARM_EXCEPTION_EL1_SERROR:
- /* We may still need to return for single-step */
- if (!(*vcpu_cpsr(vcpu) & DBG_SPSR_SS)
- && kvm_arm_handle_step_debug(vcpu, run))
- return 0;
- else
- return 1;
+ return 1;
case ARM_EXCEPTION_TRAP:
return handle_trap_exceptions(vcpu, run);
case ARM_EXCEPTION_HYP_GONE: