[PATCH v6 6/7] KVM: arm64: allow get exception information from userspace

[Dongjiu Geng]

when userspace gets SIGBUS signal, it does not know whether
this is a synchronous external abort or SError, so needs
to get the exception syndrome. This patch allows userspace
can get this values. For syndrome, only give userspace
syndrome EC and ISS.

Now we move the synchronous external abort injection logic to
userspace, when userspace injects the SEA exception to guest
OS, it needs to specify the far_el1 value, so this patch gives
the exception virtual address to userspace.

change since v5:
1. modify some patch description

Signed-off-by: Dongjiu Geng <gengdongjiu@xxxxxxxxxx>
Signed-off-by: Quanming Wu <wuquanming@xxxxxxxxxx>
---
 arch/arm64/include/uapi/asm/kvm.h |  5 +++++
 arch/arm64/kvm/guest.c            | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 9f3ca24bbcc6..514261f682b8 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -181,6 +181,11 @@ struct kvm_arch_memory_slot {
 #define KVM_REG_ARM64_SYSREG_OP2_MASK	0x0000000000000007
 #define KVM_REG_ARM64_SYSREG_OP2_SHIFT	0
 
+/* AArch64 fault registers */
+#define KVM_REG_ARM64_FAULT		(0x0014 << KVM_REG_ARM_COPROC_SHIFT)
+#define KVM_REG_ARM64_FAULT_ESR_EC_ISS	(0)
+#define KVM_REG_ARM64_FAULT_FAR		(1)
+
 #define ARM64_SYS_REG_SHIFT_MASK(x,n) \
 	(((x) << KVM_REG_ARM64_SYSREG_ ## n ## _SHIFT) & \
 	KVM_REG_ARM64_SYSREG_ ## n ## _MASK)
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 5c7f657dd207..020a644b20d7 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -128,6 +128,39 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 out:
 	return err;
 }
+static int get_fault_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+	void __user *uaddr = (void __user *)(unsigned long)reg->addr;
+	u32 value;
+	u32 id = reg->id & ~(KVM_REG_ARCH_MASK |
+			KVM_REG_SIZE_MASK | KVM_REG_ARM64_FAULT);
+
+	switch (id) {
+	case KVM_REG_ARM64_FAULT_ESR_EC_ISS:
+		/*
+		 * The user space may need to know the fault exception class
+		 * ESR_ELx.EC and instruction specific syndrome ESR_ELx.ISS
+		 */
+		value = kvm_vcpu_get_hsr(vcpu) & (ESR_ELx_EC_MASK | ESR_ELx_ISS_MASK);
+		if (copy_to_user(uaddr, &value, KVM_REG_SIZE(reg->id)) != 0)
+			return -EFAULT;
+		break;
+	case KVM_REG_ARM64_FAULT_FAR:
+		/*
+		 * When user space injects synchronized abort, it needs
+		 * to inject the faulting virtual address to guest OS, so
+		 * needs to get it from kvm.
+		 */
+		if (copy_to_user(uaddr, &(vcpu->arch.fault.far_el2),
+				KVM_REG_SIZE(reg->id)) != 0)
+			return -EFAULT;
+		break;
+	default:
+		return -ENOENT;
+	}
+	return 0;
+}
+
 
 int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 {
@@ -243,6 +276,9 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
 		return get_core_reg(vcpu, reg);
 
+	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM64_FAULT)
+		return get_fault_reg(vcpu, reg);
+
 	if (is_timer_reg(reg->id))
 		return get_timer_reg(vcpu, reg);
 
-- 
2.14.1