linux-kernel - [PATCH v3 3/3] kvm: arm64: handle single-step of userspace mmio instructions

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Date:   Thu, 16 Nov 2017 15:39:21 +0000
From:   Alex Bennée <alex.bennee@...aro.org>
To:     julien.thierry@....com, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        christoffer.dall@...aro.org, marc.zyngier@....com
Cc:     Alex Bennée <alex.bennee@...aro.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v3 3/3] kvm: arm64: handle single-step of userspace mmio instructions

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.

The kvm_arm_handle_step_debug() helper tells us if we need to return
and sets up the exit_reason for us.

Signed-off-by: Alex Bennée <alex.bennee@...aro.org>

---
v2
  - call helper directly from kvm_arch_vcpu_ioctl_run
v3
  - return 0 (ioctl success) instead of 1
---
 virt/kvm/arm/arm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 95cba0799828..b40440defca1 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -625,6 +625,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		ret = kvm_handle_mmio_return(vcpu, vcpu->run);
 		if (ret)
 			return ret;
+		if (kvm_arm_handle_step_debug(vcpu, vcpu->run))
+			return 0;
+
 	}
 
 	if (run->immediate_exit)
-- 
2.15.0